Add the OverfitModel

Summary: Introduces the OverfitModel for NeRF-style training with overfitting to one scene. It is a specific case of GenericModel. It has been disentangle to ease usage. ## General modification 1. Modularize a minimum GenericModel to introduce OverfitModel 2. Introduce OverfitModel and ensure through unit testing that it behaves like GenericModel. ## Modularization The following methods have been extracted from GenericModel to allow modularity with ManyViewModel: - get_objective is now a call to weighted_sum_losses - log_loss_weights - prepare_inputs The generic methods have been moved to an utils.py file. Simplify the code to introduce OverfitModel. Private methods like chunk_generator are now public and can now be used by ManyViewModel. Reviewed By: shapovalov Differential Revision: D43771992 fbshipit-source-id: 6102aeb21c7fdd56aa2ff9cd1dd23fd9fbf26315
2025-07-31 10:52:50 +08:00 · 2023-03-24 07:27:39 -07:00 · 2023-03-24 07:27:39 -07:00 · 813e941de5
commit 813e941de5
parent 7d8b029aae
16 changed files with 2012 additions and 201 deletions
--- a/projects/implicitron_trainer/README.md
+++ b/projects/implicitron_trainer/README.md
@ -248,7 +248,7 @@ The main object for this trainer loop is `Experiment`. It has four top-level rep
 * `data_source`: This is a `DataSourceBase` which defaults to `ImplicitronDataSource`.
 It constructs the data sets and dataloaders.
 * `model_factory`: This is a `ModelFactoryBase` which defaults to `ImplicitronModelFactory`.
-It constructs the model, which is usually an instance of implicitron's main `GenericModel` class, and can load its weights from a checkpoint.
+It constructs the model, which is usually an instance of `OverfitModel` (for NeRF-style training with overfitting to one scene) or `GenericModel` (that is able to generalize to multiple scenes by NeRFormer-style conditioning on other scene views), and can load its weights from a checkpoint.
 * `optimizer_factory`: This is an `OptimizerFactoryBase` which defaults to `ImplicitronOptimizerFactory`.
 It constructs the optimizer and can load its weights from a checkpoint.
 * `training_loop`: This is a `TrainingLoopBase` which defaults to `ImplicitronTrainingLoop` and defines the main training loop.
@ -292,6 +292,43 @@ model_GenericModel_args: GenericModel
        ╘== ReductionFeatureAggregator
 ```

+Here is the class structure of OverfitModel:
+
+```
+model_OverfitModel_args: OverfitModel
+└-- raysampler_*_args: RaySampler
+    ╘== AdaptiveRaysampler
+    ╘== NearFarRaysampler
+└-- renderer_*_args: BaseRenderer
+    ╘== MultiPassEmissionAbsorptionRenderer
+    ╘== LSTMRenderer
+    ╘== SignedDistanceFunctionRenderer
+        └-- ray_tracer_args: RayTracing
+        └-- ray_normal_coloring_network_args: RayNormalColoringNetwork
+└-- implicit_function_*_args: ImplicitFunctionBase
+    ╘== NeuralRadianceFieldImplicitFunction
+    ╘== SRNImplicitFunction
+        └-- raymarch_function_args: SRNRaymarchFunction
+        └-- pixel_generator_args: SRNPixelGenerator
+    ╘== SRNHyperNetImplicitFunction
+        └-- hypernet_args: SRNRaymarchHyperNet
+        └-- pixel_generator_args: SRNPixelGenerator
+    ╘== IdrFeatureField
+└-- coarse_implicit_function_*_args: ImplicitFunctionBase
+    ╘== NeuralRadianceFieldImplicitFunction
+    ╘== SRNImplicitFunction
+        └-- raymarch_function_args: SRNRaymarchFunction
+        └-- pixel_generator_args: SRNPixelGenerator
+    ╘== SRNHyperNetImplicitFunction
+        └-- hypernet_args: SRNRaymarchHyperNet
+        └-- pixel_generator_args: SRNPixelGenerator
+    ╘== IdrFeatureField
+```
+
+OverfitModel has been introduced to create a simple class to disantagle Nerfs which the overfit pattern
+from the GenericModel.
+
+
 Please look at the annotations of the respective classes or functions for the lists of hyperparameters.
 `tests/experiment.yaml` shows every possible option if you have no user-defined classes.

--- a/projects/implicitron_trainer/configs/overfit_base.yaml
+++ b/projects/implicitron_trainer/configs/overfit_base.yaml
@ -0,0 +1,79 @@
+defaults:
+- default_config
+- _self_
+exp_dir: ./data/exps/overfit_base/
+training_loop_ImplicitronTrainingLoop_args:
+  visdom_port: 8097
+  visualize_interval: 0
+  max_epochs: 1000
+data_source_ImplicitronDataSource_args:
+  data_loader_map_provider_class_type: SequenceDataLoaderMapProvider
+  dataset_map_provider_class_type: JsonIndexDatasetMapProvider
+  data_loader_map_provider_SequenceDataLoaderMapProvider_args:
+    dataset_length_train: 1000
+    dataset_length_val: 1
+    num_workers: 8
+  dataset_map_provider_JsonIndexDatasetMapProvider_args:
+    dataset_root: ${oc.env:CO3D_DATASET_ROOT}
+    n_frames_per_sequence: -1
+    test_on_train: true
+    test_restrict_sequence_id: 0
+    dataset_JsonIndexDataset_args:
+      load_point_clouds: false
+      mask_depths: false
+      mask_images: false
+model_factory_ImplicitronModelFactory_args:
+  model_class_type: "OverfitModel"
+  model_OverfitModel_args:
+    loss_weights:
+      loss_mask_bce: 1.0
+      loss_prev_stage_mask_bce: 1.0
+      loss_autodecoder_norm: 0.01
+      loss_rgb_mse: 1.0
+      loss_prev_stage_rgb_mse: 1.0
+    output_rasterized_mc: false
+    chunk_size_grid: 102400
+    render_image_height: 400
+    render_image_width: 400
+    share_implicit_function_across_passes: false
+    implicit_function_class_type: "NeuralRadianceFieldImplicitFunction"
+    implicit_function_NeuralRadianceFieldImplicitFunction_args:
+      n_harmonic_functions_xyz: 10
+      n_harmonic_functions_dir: 4
+      n_hidden_neurons_xyz: 256
+      n_hidden_neurons_dir: 128
+      n_layers_xyz: 8
+      append_xyz:
+      - 5
+    coarse_implicit_function_class_type: "NeuralRadianceFieldImplicitFunction"
+    coarse_implicit_function_NeuralRadianceFieldImplicitFunction_args:
+      n_harmonic_functions_xyz: 10
+      n_harmonic_functions_dir: 4
+      n_hidden_neurons_xyz: 256
+      n_hidden_neurons_dir: 128
+      n_layers_xyz: 8
+      append_xyz:
+      - 5
+    raysampler_AdaptiveRaySampler_args:
+      n_rays_per_image_sampled_from_mask: 1024
+      scene_extent: 8.0
+      n_pts_per_ray_training: 64
+      n_pts_per_ray_evaluation: 64
+      stratified_point_sampling_training: true
+      stratified_point_sampling_evaluation: false
+    renderer_MultiPassEmissionAbsorptionRenderer_args:
+      n_pts_per_ray_fine_training: 64
+      n_pts_per_ray_fine_evaluation: 64
+      append_coarse_samples_to_fine: true
+      density_noise_std_train: 1.0
+optimizer_factory_ImplicitronOptimizerFactory_args:
+  breed: Adam
+  weight_decay: 0.0
+  lr_policy: MultiStepLR
+  multistep_lr_milestones: []
+  lr: 0.0005
+  gamma: 0.1
+  momentum: 0.9
+  betas:
+  - 0.9
+  - 0.999
--- a/projects/implicitron_trainer/configs/overfit_singleseq_base.yaml
+++ b/projects/implicitron_trainer/configs/overfit_singleseq_base.yaml
@ -0,0 +1,42 @@
+defaults:
+- overfit_base
+- _self_
+data_source_ImplicitronDataSource_args:
+  data_loader_map_provider_SequenceDataLoaderMapProvider_args:
+    batch_size: 1
+    dataset_length_train: 1000
+    dataset_length_val: 1
+    num_workers: 8
+  dataset_map_provider_JsonIndexDatasetMapProvider_args:
+    assert_single_seq: true
+    n_frames_per_sequence: -1
+    test_restrict_sequence_id: 0
+    test_on_train: false
+model_factory_ImplicitronModelFactory_args:
+  model_class_type: "OverfitModel"
+  model_OverfitModel_args:
+    render_image_height: 800
+    render_image_width: 800
+    log_vars:
+    - loss_rgb_psnr_fg
+    - loss_rgb_psnr
+    - loss_eikonal
+    - loss_prev_stage_rgb_psnr
+    - loss_mask_bce
+    - loss_prev_stage_mask_bce
+    - loss_rgb_mse
+    - loss_prev_stage_rgb_mse
+    - loss_depth_abs
+    - loss_depth_abs_fg
+    - loss_kl
+    - loss_mask_neg_iou
+    - objective
+    - epoch
+    - sec/it
+optimizer_factory_ImplicitronOptimizerFactory_args:
+  lr: 0.0005
+  multistep_lr_milestones:
+  - 200
+  - 300
+training_loop_ImplicitronTrainingLoop_args:
+  max_epochs: 400
--- a/projects/implicitron_trainer/configs/overfit_singleseq_nerf_blender.yaml
+++ b/projects/implicitron_trainer/configs/overfit_singleseq_nerf_blender.yaml
@ -0,0 +1,56 @@
+defaults:
+- overfit_singleseq_base
+- _self_
+exp_dir: "./data/overfit_nerf_blender_repro/${oc.env:BLENDER_SINGLESEQ_CLASS}"
+data_source_ImplicitronDataSource_args:
+  data_loader_map_provider_SequenceDataLoaderMapProvider_args:
+    dataset_length_train: 100
+  dataset_map_provider_class_type: BlenderDatasetMapProvider
+  dataset_map_provider_BlenderDatasetMapProvider_args:
+    base_dir: ${oc.env:BLENDER_DATASET_ROOT}/${oc.env:BLENDER_SINGLESEQ_CLASS}
+    n_known_frames_for_test: null
+    object_name: ${oc.env:BLENDER_SINGLESEQ_CLASS}
+    path_manager_factory_class_type: PathManagerFactory
+    path_manager_factory_PathManagerFactory_args:
+      silence_logs: true
+
+model_factory_ImplicitronModelFactory_args:
+  model_class_type: "OverfitModel"
+  model_OverfitModel_args:
+    mask_images: false
+    raysampler_class_type: AdaptiveRaySampler
+    raysampler_AdaptiveRaySampler_args:
+      n_pts_per_ray_training: 64
+      n_pts_per_ray_evaluation: 64
+      n_rays_per_image_sampled_from_mask: 4096
+      stratified_point_sampling_training: true
+      stratified_point_sampling_evaluation: false
+      scene_extent: 2.0
+      scene_center:
+      - 0.0
+      - 0.0
+      - 0.0
+    renderer_MultiPassEmissionAbsorptionRenderer_args:
+      density_noise_std_train: 0.0
+      n_pts_per_ray_fine_training: 128
+      n_pts_per_ray_fine_evaluation: 128
+      raymarcher_EmissionAbsorptionRaymarcher_args:
+        blend_output: false
+    loss_weights:
+      loss_rgb_mse: 1.0
+      loss_prev_stage_rgb_mse: 1.0
+      loss_mask_bce: 0.0
+      loss_prev_stage_mask_bce: 0.0
+      loss_autodecoder_norm: 0.00
+
+optimizer_factory_ImplicitronOptimizerFactory_args:
+  exponential_lr_step_size: 3001
+  lr_policy: LinearExponential
+  linear_exponential_lr_milestone: 200
+
+training_loop_ImplicitronTrainingLoop_args:
+  max_epochs: 6000
+  metric_print_interval: 10
+  store_checkpoints_purge: 3
+  test_when_finished: true
+  validation_interval: 100
--- a/projects/implicitron_trainer/experiment.py
+++ b/projects/implicitron_trainer/experiment.py
@ -59,7 +59,7 @@ from pytorch3d.implicitron.dataset.data_source import (
    DataSourceBase,
    ImplicitronDataSource,
 )
-from pytorch3d.implicitron.models.generic_model import ImplicitronModelBase
+from pytorch3d.implicitron.models.base_model import ImplicitronModelBase

 from pytorch3d.implicitron.models.renderer.multipass_ea import (
    MultiPassEmissionAbsorptionRenderer,
--- a/projects/implicitron_trainer/tests/experiment.yaml
+++ b/projects/implicitron_trainer/tests/experiment.yaml
@ -561,6 +561,623 @@ model_factory_ImplicitronModelFactory_args:
          use_xavier_init: true
    view_metrics_ViewMetrics_args: {}
    regularization_metrics_RegularizationMetrics_args: {}
+  model_OverfitModel_args:
+    log_vars:
+    - loss_rgb_psnr_fg
+    - loss_rgb_psnr
+    - loss_rgb_mse
+    - loss_rgb_huber
+    - loss_depth_abs
+    - loss_depth_abs_fg
+    - loss_mask_neg_iou
+    - loss_mask_bce
+    - loss_mask_beta_prior
+    - loss_eikonal
+    - loss_density_tv
+    - loss_depth_neg_penalty
+    - loss_autodecoder_norm
+    - loss_prev_stage_rgb_mse
+    - loss_prev_stage_rgb_psnr_fg
+    - loss_prev_stage_rgb_psnr
+    - loss_prev_stage_mask_bce
+    - objective
+    - epoch
+    - sec/it
+    mask_images: true
+    mask_depths: true
+    render_image_width: 400
+    render_image_height: 400
+    mask_threshold: 0.5
+    output_rasterized_mc: false
+    bg_color:
+    - 0.0
+    - 0.0
+    - 0.0
+    chunk_size_grid: 4096
+    render_features_dimensions: 3
+    tqdm_trigger_threshold: 16
+    n_train_target_views: 1
+    sampling_mode_training: mask_sample
+    sampling_mode_evaluation: full_grid
+    global_encoder_class_type: null
+    raysampler_class_type: AdaptiveRaySampler
+    renderer_class_type: MultiPassEmissionAbsorptionRenderer
+    share_implicit_function_across_passes: false
+    implicit_function_class_type: NeuralRadianceFieldImplicitFunction
+    coarse_implicit_function_class_type: null
+    view_metrics_class_type: ViewMetrics
+    regularization_metrics_class_type: RegularizationMetrics
+    loss_weights:
+      loss_rgb_mse: 1.0
+      loss_prev_stage_rgb_mse: 1.0
+      loss_mask_bce: 0.0
+      loss_prev_stage_mask_bce: 0.0
+    global_encoder_HarmonicTimeEncoder_args:
+      n_harmonic_functions: 10
+      append_input: true
+      time_divisor: 1.0
+    global_encoder_SequenceAutodecoder_args:
+      autodecoder_args:
+        encoding_dim: 0
+        n_instances: 1
+        init_scale: 1.0
+        ignore_input: false
+    raysampler_AdaptiveRaySampler_args:
+      n_pts_per_ray_training: 64
+      n_pts_per_ray_evaluation: 64
+      n_rays_per_image_sampled_from_mask: 1024
+      n_rays_total_training: null
+      stratified_point_sampling_training: true
+      stratified_point_sampling_evaluation: false
+      scene_extent: 8.0
+      scene_center:
+      - 0.0
+      - 0.0
+      - 0.0
+    raysampler_NearFarRaySampler_args:
+      n_pts_per_ray_training: 64
+      n_pts_per_ray_evaluation: 64
+      n_rays_per_image_sampled_from_mask: 1024
+      n_rays_total_training: null
+      stratified_point_sampling_training: true
+      stratified_point_sampling_evaluation: false
+      min_depth: 0.1
+      max_depth: 8.0
+    renderer_LSTMRenderer_args:
+      num_raymarch_steps: 10
+      init_depth: 17.0
+      init_depth_noise_std: 0.0005
+      hidden_size: 16
+      n_feature_channels: 256
+      bg_color: null
+      verbose: false
+    renderer_MultiPassEmissionAbsorptionRenderer_args:
+      raymarcher_class_type: EmissionAbsorptionRaymarcher
+      n_pts_per_ray_fine_training: 64
+      n_pts_per_ray_fine_evaluation: 64
+      stratified_sampling_coarse_training: true
+      stratified_sampling_coarse_evaluation: false
+      append_coarse_samples_to_fine: true
+      density_noise_std_train: 0.0
+      return_weights: false
+      raymarcher_CumsumRaymarcher_args:
+        surface_thickness: 1
+        bg_color:
+        - 0.0
+        replicate_last_interval: false
+        background_opacity: 0.0
+        density_relu: true
+        blend_output: false
+      raymarcher_EmissionAbsorptionRaymarcher_args:
+        surface_thickness: 1
+        bg_color:
+        - 0.0
+        replicate_last_interval: false
+        background_opacity: 10000000000.0
+        density_relu: true
+        blend_output: false
+    renderer_SignedDistanceFunctionRenderer_args:
+      ray_normal_coloring_network_args:
+        feature_vector_size: 3
+        mode: idr
+        d_in: 9
+        d_out: 3
+        dims:
+        - 512
+        - 512
+        - 512
+        - 512
+        weight_norm: true
+        n_harmonic_functions_dir: 0
+        pooled_feature_dim: 0
+      bg_color:
+      - 0.0
+      soft_mask_alpha: 50.0
+      ray_tracer_args:
+        sdf_threshold: 5.0e-05
+        line_search_step: 0.5
+        line_step_iters: 1
+        sphere_tracing_iters: 10
+        n_steps: 100
+        n_secant_steps: 8
+    implicit_function_IdrFeatureField_args:
+      d_in: 3
+      d_out: 1
+      dims:
+      - 512
+      - 512
+      - 512
+      - 512
+      - 512
+      - 512
+      - 512
+      - 512
+      geometric_init: true
+      bias: 1.0
+      skip_in: []
+      weight_norm: true
+      n_harmonic_functions_xyz: 0
+      pooled_feature_dim: 0
+    implicit_function_NeRFormerImplicitFunction_args:
+      n_harmonic_functions_xyz: 10
+      n_harmonic_functions_dir: 4
+      n_hidden_neurons_dir: 128
+      input_xyz: true
+      xyz_ray_dir_in_camera_coords: false
+      transformer_dim_down_factor: 2.0
+      n_hidden_neurons_xyz: 80
+      n_layers_xyz: 2
+      append_xyz:
+      - 1
+    implicit_function_NeuralRadianceFieldImplicitFunction_args:
+      n_harmonic_functions_xyz: 10
+      n_harmonic_functions_dir: 4
+      n_hidden_neurons_dir: 128
+      input_xyz: true
+      xyz_ray_dir_in_camera_coords: false
+      transformer_dim_down_factor: 1.0
+      n_hidden_neurons_xyz: 256
+      n_layers_xyz: 8
+      append_xyz:
+      - 5
+    implicit_function_SRNHyperNetImplicitFunction_args:
+      latent_dim_hypernet: 0
+      hypernet_args:
+        n_harmonic_functions: 3
+        n_hidden_units: 256
+        n_layers: 2
+        n_hidden_units_hypernet: 256
+        n_layers_hypernet: 1
+        in_features: 3
+        out_features: 256
+        xyz_in_camera_coords: false
+      pixel_generator_args:
+        n_harmonic_functions: 4
+        n_hidden_units: 256
+        n_hidden_units_color: 128
+        n_layers: 2
+        in_features: 256
+        out_features: 3
+        ray_dir_in_camera_coords: false
+    implicit_function_SRNImplicitFunction_args:
+      raymarch_function_args:
+        n_harmonic_functions: 3
+        n_hidden_units: 256
+        n_layers: 2
+        in_features: 3
+        out_features: 256
+        xyz_in_camera_coords: false
+        raymarch_function: null
+      pixel_generator_args:
+        n_harmonic_functions: 4
+        n_hidden_units: 256
+        n_hidden_units_color: 128
+        n_layers: 2
+        in_features: 256
+        out_features: 3
+        ray_dir_in_camera_coords: false
+    implicit_function_VoxelGridImplicitFunction_args:
+      harmonic_embedder_xyz_density_args:
+        n_harmonic_functions: 6
+        omega_0: 1.0
+        logspace: true
+        append_input: true
+      harmonic_embedder_xyz_color_args:
+        n_harmonic_functions: 6
+        omega_0: 1.0
+        logspace: true
+        append_input: true
+      harmonic_embedder_dir_color_args:
+        n_harmonic_functions: 6
+        omega_0: 1.0
+        logspace: true
+        append_input: true
+      decoder_density_class_type: MLPDecoder
+      decoder_color_class_type: MLPDecoder
+      use_multiple_streams: true
+      xyz_ray_dir_in_camera_coords: false
+      scaffold_calculating_epochs: []
+      scaffold_resolution:
+      - 128
+      - 128
+      - 128
+      scaffold_empty_space_threshold: 0.001
+      scaffold_occupancy_chunk_size: -1
+      scaffold_max_pool_kernel_size: 3
+      scaffold_filter_points: true
+      volume_cropping_epochs: []
+      voxel_grid_density_args:
+        voxel_grid_class_type: FullResolutionVoxelGrid
+        extents:
+        - 2.0
+        - 2.0
+        - 2.0
+        translation:
+        - 0.0
+        - 0.0
+        - 0.0
+        init_std: 0.1
+        init_mean: 0.0
+        hold_voxel_grid_as_parameters: true
+        param_groups: {}
+        voxel_grid_CPFactorizedVoxelGrid_args:
+          align_corners: true
+          padding: zeros
+          mode: bilinear
+          n_features: 1
+          resolution_changes:
+            0:
+            - 128
+            - 128
+            - 128
+          n_components: 24
+          basis_matrix: true
+        voxel_grid_FullResolutionVoxelGrid_args:
+          align_corners: true
+          padding: zeros
+          mode: bilinear
+          n_features: 1
+          resolution_changes:
+            0:
+            - 128
+            - 128
+            - 128
+        voxel_grid_VMFactorizedVoxelGrid_args:
+          align_corners: true
+          padding: zeros
+          mode: bilinear
+          n_features: 1
+          resolution_changes:
+            0:
+            - 128
+            - 128
+            - 128
+          n_components: null
+          distribution_of_components: null
+          basis_matrix: true
+      voxel_grid_color_args:
+        voxel_grid_class_type: FullResolutionVoxelGrid
+        extents:
+        - 2.0
+        - 2.0
+        - 2.0
+        translation:
+        - 0.0
+        - 0.0
+        - 0.0
+        init_std: 0.1
+        init_mean: 0.0
+        hold_voxel_grid_as_parameters: true
+        param_groups: {}
+        voxel_grid_CPFactorizedVoxelGrid_args:
+          align_corners: true
+          padding: zeros
+          mode: bilinear
+          n_features: 1
+          resolution_changes:
+            0:
+            - 128
+            - 128
+            - 128
+          n_components: 24
+          basis_matrix: true
+        voxel_grid_FullResolutionVoxelGrid_args:
+          align_corners: true
+          padding: zeros
+          mode: bilinear
+          n_features: 1
+          resolution_changes:
+            0:
+            - 128
+            - 128
+            - 128
+        voxel_grid_VMFactorizedVoxelGrid_args:
+          align_corners: true
+          padding: zeros
+          mode: bilinear
+          n_features: 1
+          resolution_changes:
+            0:
+            - 128
+            - 128
+            - 128
+          n_components: null
+          distribution_of_components: null
+          basis_matrix: true
+      decoder_density_ElementwiseDecoder_args:
+        scale: 1.0
+        shift: 0.0
+        operation: IDENTITY
+      decoder_density_MLPDecoder_args:
+        param_groups: {}
+        network_args:
+          n_layers: 8
+          output_dim: 256
+          skip_dim: 39
+          hidden_dim: 256
+          input_skips:
+          - 5
+          skip_affine_trans: false
+          last_layer_bias_init: null
+          last_activation: RELU
+          use_xavier_init: true
+      decoder_color_ElementwiseDecoder_args:
+        scale: 1.0
+        shift: 0.0
+        operation: IDENTITY
+      decoder_color_MLPDecoder_args:
+        param_groups: {}
+        network_args:
+          n_layers: 8
+          output_dim: 256
+          skip_dim: 39
+          hidden_dim: 256
+          input_skips:
+          - 5
+          skip_affine_trans: false
+          last_layer_bias_init: null
+          last_activation: RELU
+          use_xavier_init: true
+    coarse_implicit_function_IdrFeatureField_args:
+      d_in: 3
+      d_out: 1
+      dims:
+      - 512
+      - 512
+      - 512
+      - 512
+      - 512
+      - 512
+      - 512
+      - 512
+      geometric_init: true
+      bias: 1.0
+      skip_in: []
+      weight_norm: true
+      n_harmonic_functions_xyz: 0
+      pooled_feature_dim: 0
+    coarse_implicit_function_NeRFormerImplicitFunction_args:
+      n_harmonic_functions_xyz: 10
+      n_harmonic_functions_dir: 4
+      n_hidden_neurons_dir: 128
+      input_xyz: true
+      xyz_ray_dir_in_camera_coords: false
+      transformer_dim_down_factor: 2.0
+      n_hidden_neurons_xyz: 80
+      n_layers_xyz: 2
+      append_xyz:
+      - 1
+    coarse_implicit_function_NeuralRadianceFieldImplicitFunction_args:
+      n_harmonic_functions_xyz: 10
+      n_harmonic_functions_dir: 4
+      n_hidden_neurons_dir: 128
+      input_xyz: true
+      xyz_ray_dir_in_camera_coords: false
+      transformer_dim_down_factor: 1.0
+      n_hidden_neurons_xyz: 256
+      n_layers_xyz: 8
+      append_xyz:
+      - 5
+    coarse_implicit_function_SRNHyperNetImplicitFunction_args:
+      latent_dim_hypernet: 0
+      hypernet_args:
+        n_harmonic_functions: 3
+        n_hidden_units: 256
+        n_layers: 2
+        n_hidden_units_hypernet: 256
+        n_layers_hypernet: 1
+        in_features: 3
+        out_features: 256
+        xyz_in_camera_coords: false
+      pixel_generator_args:
+        n_harmonic_functions: 4
+        n_hidden_units: 256
+        n_hidden_units_color: 128
+        n_layers: 2
+        in_features: 256
+        out_features: 3
+        ray_dir_in_camera_coords: false
+    coarse_implicit_function_SRNImplicitFunction_args:
+      raymarch_function_args:
+        n_harmonic_functions: 3
+        n_hidden_units: 256
+        n_layers: 2
+        in_features: 3
+        out_features: 256
+        xyz_in_camera_coords: false
+        raymarch_function: null
+      pixel_generator_args:
+        n_harmonic_functions: 4
+        n_hidden_units: 256
+        n_hidden_units_color: 128
+        n_layers: 2
+        in_features: 256
+        out_features: 3
+        ray_dir_in_camera_coords: false
+    coarse_implicit_function_VoxelGridImplicitFunction_args:
+      harmonic_embedder_xyz_density_args:
+        n_harmonic_functions: 6
+        omega_0: 1.0
+        logspace: true
+        append_input: true
+      harmonic_embedder_xyz_color_args:
+        n_harmonic_functions: 6
+        omega_0: 1.0
+        logspace: true
+        append_input: true
+      harmonic_embedder_dir_color_args:
+        n_harmonic_functions: 6
+        omega_0: 1.0
+        logspace: true
+        append_input: true
+      decoder_density_class_type: MLPDecoder
+      decoder_color_class_type: MLPDecoder
+      use_multiple_streams: true
+      xyz_ray_dir_in_camera_coords: false
+      scaffold_calculating_epochs: []
+      scaffold_resolution:
+      - 128
+      - 128
+      - 128
+      scaffold_empty_space_threshold: 0.001
+      scaffold_occupancy_chunk_size: -1
+      scaffold_max_pool_kernel_size: 3
+      scaffold_filter_points: true
+      volume_cropping_epochs: []
+      voxel_grid_density_args:
+        voxel_grid_class_type: FullResolutionVoxelGrid
+        extents:
+        - 2.0
+        - 2.0
+        - 2.0
+        translation:
+        - 0.0
+        - 0.0
+        - 0.0
+        init_std: 0.1
+        init_mean: 0.0
+        hold_voxel_grid_as_parameters: true
+        param_groups: {}
+        voxel_grid_CPFactorizedVoxelGrid_args:
+          align_corners: true
+          padding: zeros
+          mode: bilinear
+          n_features: 1
+          resolution_changes:
+            0:
+            - 128
+            - 128
+            - 128
+          n_components: 24
+          basis_matrix: true
+        voxel_grid_FullResolutionVoxelGrid_args:
+          align_corners: true
+          padding: zeros
+          mode: bilinear
+          n_features: 1
+          resolution_changes:
+            0:
+            - 128
+            - 128
+            - 128
+        voxel_grid_VMFactorizedVoxelGrid_args:
+          align_corners: true
+          padding: zeros
+          mode: bilinear
+          n_features: 1
+          resolution_changes:
+            0:
+            - 128
+            - 128
+            - 128
+          n_components: null
+          distribution_of_components: null
+          basis_matrix: true
+      voxel_grid_color_args:
+        voxel_grid_class_type: FullResolutionVoxelGrid
+        extents:
+        - 2.0
+        - 2.0
+        - 2.0
+        translation:
+        - 0.0
+        - 0.0
+        - 0.0
+        init_std: 0.1
+        init_mean: 0.0
+        hold_voxel_grid_as_parameters: true
+        param_groups: {}
+        voxel_grid_CPFactorizedVoxelGrid_args:
+          align_corners: true
+          padding: zeros
+          mode: bilinear
+          n_features: 1
+          resolution_changes:
+            0:
+            - 128
+            - 128
+            - 128
+          n_components: 24
+          basis_matrix: true
+        voxel_grid_FullResolutionVoxelGrid_args:
+          align_corners: true
+          padding: zeros
+          mode: bilinear
+          n_features: 1
+          resolution_changes:
+            0:
+            - 128
+            - 128
+            - 128
+        voxel_grid_VMFactorizedVoxelGrid_args:
+          align_corners: true
+          padding: zeros
+          mode: bilinear
+          n_features: 1
+          resolution_changes:
+            0:
+            - 128
+            - 128
+            - 128
+          n_components: null
+          distribution_of_components: null
+          basis_matrix: true
+      decoder_density_ElementwiseDecoder_args:
+        scale: 1.0
+        shift: 0.0
+        operation: IDENTITY
+      decoder_density_MLPDecoder_args:
+        param_groups: {}
+        network_args:
+          n_layers: 8
+          output_dim: 256
+          skip_dim: 39
+          hidden_dim: 256
+          input_skips:
+          - 5
+          skip_affine_trans: false
+          last_layer_bias_init: null
+          last_activation: RELU
+          use_xavier_init: true
+      decoder_color_ElementwiseDecoder_args:
+        scale: 1.0
+        shift: 0.0
+        operation: IDENTITY
+      decoder_color_MLPDecoder_args:
+        param_groups: {}
+        network_args:
+          n_layers: 8
+          output_dim: 256
+          skip_dim: 39
+          hidden_dim: 256
+          input_skips:
+          - 5
+          skip_affine_trans: false
+          last_layer_bias_init: null
+          last_activation: RELU
+          use_xavier_init: true
+    view_metrics_ViewMetrics_args: {}
+    regularization_metrics_RegularizationMetrics_args: {}
 optimizer_factory_ImplicitronOptimizerFactory_args:
  betas:
  - 0.9
--- a/projects/implicitron_trainer/tests/test_experiment.py
+++ b/projects/implicitron_trainer/tests/test_experiment.py
@ -141,7 +141,11 @@ class TestExperiment(unittest.TestCase):
        # Check that all the pre-prepared configs are valid.
        config_files = []

-        for pattern in ("repro_singleseq*.yaml", "repro_multiseq*.yaml"):
+        for pattern in (
+            "repro_singleseq*.yaml",
+            "repro_multiseq*.yaml",
+            "overfit_singleseq*.yaml",
+        ):
            config_files.extend(
                [
                    f
--- a/pytorch3d/implicitron/models/init.py
+++ b/pytorch3d/implicitron/models/init.py
@ -3,3 +3,8 @@
 #
 # This source code is licensed under the BSD-style license found in the
 # LICENSE file in the root directory of this source tree.
+
+# Allows to register the models
+# see: pytorch3d.implicitron.tools.config.registry:register
+from pytorch3d.implicitron.models.generic_model import GenericModel
+from pytorch3d.implicitron.models.overfit_model import OverfitModel
--- a/pytorch3d/implicitron/models/base_model.py
+++ b/pytorch3d/implicitron/models/base_model.py
@ -8,11 +8,11 @@ from dataclasses import dataclass, field
 from typing import Any, Dict, List, Optional

 import torch
+
+from pytorch3d.implicitron.models.renderer.base import EvaluationMode
 from pytorch3d.implicitron.tools.config import ReplaceableBase
 from pytorch3d.renderer.cameras import CamerasBase

-from .renderer.base import EvaluationMode
-

@dataclass
 class ImplicitronRender:
--- a/pytorch3d/implicitron/models/generic_model.py
+++ b/pytorch3d/implicitron/models/generic_model.py
@ -9,14 +9,11 @@
 # which are part of implicitron. They ensure that the registry is prepopulated.

 import logging
-import warnings
 from dataclasses import field
 from typing import Any, Dict, List, Optional, Tuple, TYPE_CHECKING, Union

 import torch
-import tqdm
 from omegaconf import DictConfig
-from pytorch3d.common.compat import prod

 from pytorch3d.implicitron.models.base_model import (
    ImplicitronModelBase,
@ -33,11 +30,9 @@ from pytorch3d.implicitron.models.implicit_function.idr_feature_field import (
 )
 from pytorch3d.implicitron.models.implicit_function.neural_radiance_field import (  # noqa
    NeRFormerImplicitFunction,
-    NeuralRadianceFieldImplicitFunction,
 )
 from pytorch3d.implicitron.models.implicit_function.scene_representation_networks import (  # noqa
    SRNHyperNetImplicitFunction,
-    SRNImplicitFunction,
 )
 from pytorch3d.implicitron.models.implicit_function.voxel_grid_implicit_function import (  # noqa
    VoxelGridImplicitFunction,
@ -63,8 +58,16 @@ from pytorch3d.implicitron.models.renderer.ray_sampler import RaySamplerBase
 from pytorch3d.implicitron.models.renderer.sdf_renderer import (  # noqa
    SignedDistanceFunctionRenderer,
 )
+
+from pytorch3d.implicitron.models.utils import (
+    apply_chunked,
+    chunk_generator,
+    log_loss_weights,
+    preprocess_input,
+    weighted_sum_losses,
+)
 from pytorch3d.implicitron.models.view_pooler.view_pooler import ViewPooler
-from pytorch3d.implicitron.tools import image_utils, vis_utils
+from pytorch3d.implicitron.tools import vis_utils
 from pytorch3d.implicitron.tools.config import (
    expand_args_fields,
    registry,
@ -72,7 +75,6 @@ from pytorch3d.implicitron.tools.config import (
 )

 from pytorch3d.implicitron.tools.rasterize_mc import rasterize_sparse_ray_bundle
-from pytorch3d.implicitron.tools.utils import cat_dataclass
 from pytorch3d.renderer import utils as rend_utils
 from pytorch3d.renderer.cameras import CamerasBase

@ -323,7 +325,7 @@ class GenericModel(ImplicitronModelBase):  # pyre-ignore: 13

        self._implicit_functions = self._construct_implicit_functions()

-        self.log_loss_weights()
+        log_loss_weights(self.loss_weights, logger)

    def forward(
        self,
@ -367,8 +369,14 @@ class GenericModel(ImplicitronModelBase):  # pyre-ignore: 13
            preds: A dictionary containing all outputs of the forward pass including the
                rendered images, depths, masks, losses and other metrics.
        """
-        image_rgb, fg_probability, depth_map = self._preprocess_input(
-            image_rgb, fg_probability, depth_map
+        image_rgb, fg_probability, depth_map = preprocess_input(
+            image_rgb,
+            fg_probability,
+            depth_map,
+            self.mask_images,
+            self.mask_depths,
+            self.mask_threshold,
+            self.bg_color,
        )

        # Obtain the batch size from the camera as this is the only required input.
@ -453,12 +461,12 @@ class GenericModel(ImplicitronModelBase):  # pyre-ignore: 13
        for func in self._implicit_functions:
            func.bind_args(**custom_args)

-        chunked_renderer_inputs = {}
+        inputs_to_be_chunked = {}
        if fg_probability is not None and self.renderer.requires_object_mask():
            sampled_fb_prob = rend_utils.ndc_grid_sample(
                fg_probability[:n_targets], ray_bundle.xys, mode="nearest"
            )
-            chunked_renderer_inputs["object_mask"] = sampled_fb_prob > 0.5
+            inputs_to_be_chunked["object_mask"] = sampled_fb_prob > 0.5

        # (5)-(6) Implicit function evaluation and Rendering
        rendered = self._render(
@ -466,7 +474,7 @@ class GenericModel(ImplicitronModelBase):  # pyre-ignore: 13
            sampling_mode=sampling_mode,
            evaluation_mode=evaluation_mode,
            implicit_functions=self._implicit_functions,
-            chunked_inputs=chunked_renderer_inputs,
+            inputs_to_be_chunked=inputs_to_be_chunked,
        )

        # Unbind the custom arguments to prevent pytorch from storing
@ -530,30 +538,18 @@ class GenericModel(ImplicitronModelBase):  # pyre-ignore: 13
            raise AssertionError("Unreachable state")

        # (7) Compute losses
-        # finally get the optimization objective using self.loss_weights
        objective = self._get_objective(preds)
        if objective is not None:
            preds["objective"] = objective

        return preds

-    def _get_objective(self, preds) -> Optional[torch.Tensor]:
+    def _get_objective(self, preds: Dict[str, torch.Tensor]) -> Optional[torch.Tensor]:
        """
        A helper function to compute the overall loss as the dot product
        of individual loss functions with the corresponding weights.
        """
-        losses_weighted = [
-            preds[k] * float(w)
-            for k, w in self.loss_weights.items()
-            if (k in preds and w != 0.0)
-        ]
-        if len(losses_weighted) == 0:
-            warnings.warn("No main objective found.")
-            return None
-        loss = sum(losses_weighted)
-        assert torch.is_tensor(loss)
-        # pyre-fixme[7]: Expected `Optional[Tensor]` but got `int`.
-        return loss
+        return weighted_sum_losses(preds, self.loss_weights)

    def visualize(
        self,
@ -585,7 +581,7 @@ class GenericModel(ImplicitronModelBase):  # pyre-ignore: 13
        self,
        *,
        ray_bundle: ImplicitronRayBundle,
-        chunked_inputs: Dict[str, torch.Tensor],
+        inputs_to_be_chunked: Dict[str, torch.Tensor],
        sampling_mode: RenderSamplingMode,
        **kwargs,
    ) -> RendererOutput:
@ -593,7 +589,7 @@ class GenericModel(ImplicitronModelBase):  # pyre-ignore: 13
        Args:
            ray_bundle: A `ImplicitronRayBundle` object containing the parametrizations of the
                sampled rendering rays.
-            chunked_inputs: A collection of tensor of shape `(B, _, H, W)`. E.g.
+            inputs_to_be_chunked: A collection of tensor of shape `(B, _, H, W)`. E.g.
                SignedDistanceFunctionRenderer requires "object_mask", shape
                (B, 1, H, W), the silhouette of the object in the image. When
                chunking, they are passed to the renderer as shape
@ -605,30 +601,27 @@ class GenericModel(ImplicitronModelBase):  # pyre-ignore: 13
            An instance of RendererOutput
        """
        if sampling_mode == RenderSamplingMode.FULL_GRID and self.chunk_size_grid > 0:
-            return _apply_chunked(
+            return apply_chunked(
                self.renderer,
-                _chunk_generator(
+                chunk_generator(
                    self.chunk_size_grid,
                    ray_bundle,
-                    chunked_inputs,
+                    inputs_to_be_chunked,
                    self.tqdm_trigger_threshold,
                    **kwargs,
                ),
-                lambda batch: _tensor_collator(batch, ray_bundle.lengths.shape[:-1]),
+                lambda batch: torch.cat(batch, dim=1).reshape(
+                    *ray_bundle.lengths.shape[:-1], -1
+                ),
            )
        else:
            # pyre-fixme[29]: `BaseRenderer` is not a function.
            return self.renderer(
                ray_bundle=ray_bundle,
-                **chunked_inputs,
+                **inputs_to_be_chunked,
                **kwargs,
            )

-    def _get_global_encoder_encoding_dim(self) -> int:
-        if self.global_encoder is None:
-            return 0
-        return self.global_encoder.get_encoding_dim()
-
    def _get_viewpooled_feature_dim(self) -> int:
        if self.view_pooler is None:
            return 0
@ -720,30 +713,29 @@ class GenericModel(ImplicitronModelBase):  # pyre-ignore: 13
        function(s) are initialized.
        """
        extra_args = {}
+        global_encoder_dim = (
+            0 if self.global_encoder is None else self.global_encoder.get_encoding_dim()
+        )
+        viewpooled_feature_dim = self._get_viewpooled_feature_dim()
+
        if self.implicit_function_class_type in (
            "NeuralRadianceFieldImplicitFunction",
            "NeRFormerImplicitFunction",
        ):
-            extra_args["latent_dim"] = (
-                self._get_viewpooled_feature_dim()
-                + self._get_global_encoder_encoding_dim()
-            )
+            extra_args["latent_dim"] = viewpooled_feature_dim + global_encoder_dim
            extra_args["color_dim"] = self.render_features_dimensions

        if self.implicit_function_class_type == "IdrFeatureField":
            extra_args["feature_vector_size"] = self.render_features_dimensions
-            extra_args["encoding_dim"] = self._get_global_encoder_encoding_dim()
+            extra_args["encoding_dim"] = global_encoder_dim

        if self.implicit_function_class_type == "SRNImplicitFunction":
-            extra_args["latent_dim"] = (
-                self._get_viewpooled_feature_dim()
-                + self._get_global_encoder_encoding_dim()
-            )
+            extra_args["latent_dim"] = viewpooled_feature_dim + global_encoder_dim

        # srn_hypernet preprocessing
        if self.implicit_function_class_type == "SRNHyperNetImplicitFunction":
-            extra_args["latent_dim"] = self._get_viewpooled_feature_dim()
-            extra_args["latent_dim_hypernet"] = self._get_global_encoder_encoding_dim()
+            extra_args["latent_dim"] = viewpooled_feature_dim
+            extra_args["latent_dim_hypernet"] = global_encoder_dim

        # check that for srn, srn_hypernet, idr we have self.num_passes=1
        implicit_function_type = registry.get(
@ -770,147 +762,3 @@ class GenericModel(ImplicitronModelBase):  # pyre-ignore: 13
            for _ in range(self.num_passes)
        ]
        return torch.nn.ModuleList(implicit_functions_list)
-
-    def log_loss_weights(self) -> None:
-        """
-        Print a table of the loss weights.
-        """
-        loss_weights_message = (
-            "-------\nloss_weights:\n"
-            + "\n".join(f"{k:40s}: {w:1.2e}" for k, w in self.loss_weights.items())
-            + "-------"
-        )
-        logger.info(loss_weights_message)
-
-    def _preprocess_input(
-        self,
-        image_rgb: Optional[torch.Tensor],
-        fg_probability: Optional[torch.Tensor],
-        depth_map: Optional[torch.Tensor],
-    ) -> Tuple[Optional[torch.Tensor], Optional[torch.Tensor], Optional[torch.Tensor]]:
-        """
-        Helper function to preprocess the input images and optional depth maps
-        to apply masking if required.
-
-        Args:
-            image_rgb: A tensor of shape `(B, 3, H, W)` containing a batch of rgb images
-                corresponding to the source viewpoints from which features will be extracted
-            fg_probability: A tensor of shape `(B, 1, H, W)` containing a batch
-                of foreground masks with values in [0, 1].
-            depth_map: A tensor of shape `(B, 1, H, W)` containing a batch of depth maps.
-
-        Returns:
-            Modified image_rgb, fg_mask, depth_map
-        """
-        if image_rgb is not None and image_rgb.ndim == 3:
-            # The FrameData object is used for both frames and batches of frames,
-            # and a user might get this error if those were confused.
-            # Perhaps a user has a FrameData `fd` representing a single frame and
-            # wrote something like `model(**fd)` instead of
-            # `model(**fd.collate([fd]))`.
-            raise ValueError(
-                "Model received unbatched inputs. "
-                + "Perhaps they came from a FrameData which had not been collated."
-            )
-
-        fg_mask = fg_probability
-        if fg_mask is not None and self.mask_threshold > 0.0:
-            # threshold masks
-            warnings.warn("Thresholding masks!")
-            fg_mask = (fg_mask >= self.mask_threshold).type_as(fg_mask)
-
-        if self.mask_images and fg_mask is not None and image_rgb is not None:
-            # mask the image
-            warnings.warn("Masking images!")
-            image_rgb = image_utils.mask_background(
-                image_rgb, fg_mask, dim_color=1, bg_color=torch.tensor(self.bg_color)
-            )
-
-        if self.mask_depths and fg_mask is not None and depth_map is not None:
-            # mask the depths
-            assert (
-                self.mask_threshold > 0.0
-            ), "Depths should be masked only with thresholded masks"
-            warnings.warn("Masking depths!")
-            depth_map = depth_map * fg_mask
-
-        return image_rgb, fg_mask, depth_map
-
-
-def _apply_chunked(func, chunk_generator, tensor_collator):
-    """
-    Helper function to apply a function on a sequence of
-    chunked inputs yielded by a generator and collate
-    the result.
-    """
-    processed_chunks = [
-        func(*chunk_args, **chunk_kwargs)
-        for chunk_args, chunk_kwargs in chunk_generator
-    ]
-
-    return cat_dataclass(processed_chunks, tensor_collator)
-
-
-def _tensor_collator(batch, new_dims) -> torch.Tensor:
-    """
-    Helper function to reshape the batch to the desired shape
-    """
-    return torch.cat(batch, dim=1).reshape(*new_dims, -1)
-
-
-def _chunk_generator(
-    chunk_size: int,
-    ray_bundle: ImplicitronRayBundle,
-    chunked_inputs: Dict[str, torch.Tensor],
-    tqdm_trigger_threshold: int,
-    *args,
-    **kwargs,
-):
-    """
-    Helper function which yields chunks of rays from the
-    input ray_bundle, to be used when the number of rays is
-    large and will not fit in memory for rendering.
-    """
-    (
-        batch_size,
-        *spatial_dim,
-        n_pts_per_ray,
-    ) = ray_bundle.lengths.shape  # B x ... x n_pts_per_ray
-    if n_pts_per_ray > 0 and chunk_size % n_pts_per_ray != 0:
-        raise ValueError(
-            f"chunk_size_grid ({chunk_size}) should be divisible "
-            f"by n_pts_per_ray ({n_pts_per_ray})"
-        )
-
-    n_rays = prod(spatial_dim)
-    # special handling for raytracing-based methods
-    n_chunks = -(-n_rays * max(n_pts_per_ray, 1) // chunk_size)
-    chunk_size_in_rays = -(-n_rays // n_chunks)
-
-    iter = range(0, n_rays, chunk_size_in_rays)
-    if len(iter) >= tqdm_trigger_threshold:
-        iter = tqdm.tqdm(iter)
-
-    def _safe_slice(
-        tensor: Optional[torch.Tensor], start_idx: int, end_idx: int
-    ) -> Any:
-        return tensor[start_idx:end_idx] if tensor is not None else None
-
-    for start_idx in iter:
-        end_idx = min(start_idx + chunk_size_in_rays, n_rays)
-        ray_bundle_chunk = ImplicitronRayBundle(
-            origins=ray_bundle.origins.reshape(batch_size, -1, 3)[:, start_idx:end_idx],
-            directions=ray_bundle.directions.reshape(batch_size, -1, 3)[
-                :, start_idx:end_idx
-            ],
-            lengths=ray_bundle.lengths.reshape(batch_size, n_rays, n_pts_per_ray)[
-                :, start_idx:end_idx
-            ],
-            xys=ray_bundle.xys.reshape(batch_size, -1, 2)[:, start_idx:end_idx],
-            camera_ids=_safe_slice(ray_bundle.camera_ids, start_idx, end_idx),
-            camera_counts=_safe_slice(ray_bundle.camera_counts, start_idx, end_idx),
-        )
-        extra_args = kwargs.copy()
-        for k, v in chunked_inputs.items():
-            extra_args[k] = v.flatten(2)[:, :, start_idx:end_idx]
-        yield [ray_bundle_chunk, *args], extra_args
--- a/pytorch3d/implicitron/models/overfit_model.py
+++ b/pytorch3d/implicitron/models/overfit_model.py
@ -0,0 +1,639 @@
+# Copyright (c) Meta Platforms, Inc. and affiliates.
+# All rights reserved.
+#
+# This source code is licensed under the BSD-style license found in the
+# LICENSE file in the root directory of this source tree.
+
+
+# Note: The #noqa comments below are for unused imports of pluggable implementations
+# which are part of implicitron. They ensure that the registry is prepopulated.
+
+import functools
+import logging
+from dataclasses import field
+from typing import Any, Callable, Dict, List, Optional, Tuple, TYPE_CHECKING, Union
+
+import torch
+from omegaconf import DictConfig
+
+from pytorch3d.implicitron.models.base_model import (
+    ImplicitronModelBase,
+    ImplicitronRender,
+)
+from pytorch3d.implicitron.models.global_encoder.global_encoder import GlobalEncoderBase
+from pytorch3d.implicitron.models.implicit_function.base import ImplicitFunctionBase
+from pytorch3d.implicitron.models.metrics import (
+    RegularizationMetricsBase,
+    ViewMetricsBase,
+)
+
+from pytorch3d.implicitron.models.renderer.base import (
+    BaseRenderer,
+    EvaluationMode,
+    ImplicitronRayBundle,
+    RendererOutput,
+    RenderSamplingMode,
+)
+from pytorch3d.implicitron.models.renderer.ray_sampler import RaySamplerBase
+from pytorch3d.implicitron.models.utils import (
+    apply_chunked,
+    chunk_generator,
+    log_loss_weights,
+    preprocess_input,
+    weighted_sum_losses,
+)
+from pytorch3d.implicitron.tools import vis_utils
+from pytorch3d.implicitron.tools.config import (
+    expand_args_fields,
+    registry,
+    run_auto_creation,
+)
+
+from pytorch3d.implicitron.tools.rasterize_mc import rasterize_sparse_ray_bundle
+from pytorch3d.renderer import utils as rend_utils
+from pytorch3d.renderer.cameras import CamerasBase
+
+
+if TYPE_CHECKING:
+    from visdom import Visdom
+logger = logging.getLogger(__name__)
+
+IMPLICIT_FUNCTION_ARGS_TO_REMOVE: List[str] = [
+    "feature_vector_size",
+    "encoding_dim",
+    "latent_dim",
+    "color_dim",
+]
+
+
+@registry.register
+class OverfitModel(ImplicitronModelBase):  # pyre-ignore: 13
+    """
+    OverfitModel is a wrapper for the neural implicit
+    rendering and reconstruction pipeline which consists
+    of the following sequence of 4 steps:
+
+
+        (1) Ray Sampling
+        ------------------
+        Rays are sampled from an image grid based on the target view(s).
+                │
+                ▼
+        (2) Implicit Function Evaluation
+        ------------------
+        Evaluate the implicit function(s) at the sampled ray points
+        (also optionally pass in a global encoding from global_encoder).
+                │
+                ▼
+        (3) Rendering
+        ------------------
+        Render the image into the target cameras by raymarching along
+        the sampled rays and aggregating the colors and densities
+        output by the implicit function in (2).
+                │
+                ▼
+        (4) Loss Computation
+        ------------------
+        Compute losses based on the predicted target image(s).
+
+
+    The `forward` function of OverfitModel executes
+    this sequence of steps. Currently, steps 1, 2, 3
+    can be customized by intializing a subclass of the appropriate
+    base class and adding the newly created module to the registry.
+    Please see https://github.com/facebookresearch/pytorch3d/blob/main/projects/implicitron_trainer/README.md#custom-plugins
+    for more details on how to create and register a custom component.
+
+    In the config .yaml files for experiments, the parameters below are
+    contained in the
+    `model_factory_ImplicitronModelFactory_args.model_OverfitModel_args`
+    node. As OverfitModel derives from ReplaceableBase, the input arguments are
+    parsed by the run_auto_creation function to initialize the
+    necessary member modules. Please see implicitron_trainer/README.md
+    for more details on this process.
+
+    Args:
+        mask_images: Whether or not to mask the RGB image background given the
+            foreground mask (the `fg_probability` argument of `GenericModel.forward`)
+        mask_depths: Whether or not to mask the depth image background given the
+            foreground mask (the `fg_probability` argument of `GenericModel.forward`)
+        render_image_width: Width of the output image to render
+        render_image_height: Height of the output image to render
+        mask_threshold: If greater than 0.0, the foreground mask is
+            thresholded by this value before being applied to the RGB/Depth images
+        output_rasterized_mc: If True, visualize the Monte-Carlo pixel renders by
+            splatting onto an image grid. Default: False.
+        bg_color: RGB values for setting the background color of input image
+            if mask_images=True. Defaults to (0.0, 0.0, 0.0). Each renderer has its own
+            way to determine the background color of its output, unrelated to this.
+        chunk_size_grid: The total number of points which can be rendered
+            per chunk. This is used to compute the number of rays used
+            per chunk when the chunked version of the renderer is used (in order
+            to fit rendering on all rays in memory)
+        render_features_dimensions: The number of output features to render.
+            Defaults to 3, corresponding to RGB images.
+        sampling_mode_training: The sampling method to use during training. Must be
+            a value from the RenderSamplingMode Enum.
+        sampling_mode_evaluation: Same as above but for evaluation.
+        global_encoder_class_type: The name of the class to use for global_encoder,
+            which must be available in the registry. Or `None` to disable global encoder.
+        global_encoder: An instance of `GlobalEncoder`. This is used to generate an encoding
+            of the image (referred to as the global_code) that can be used to model aspects of
+            the scene such as multiple objects or morphing objects. It is up to the implicit
+            function definition how to use it, but the most typical way is to broadcast and
+            concatenate to the other inputs for the implicit function.
+        raysampler_class_type: The name of the raysampler class which is available
+            in the global registry.
+        raysampler: An instance of RaySampler which is used to emit
+            rays from the target view(s).
+        renderer_class_type: The name of the renderer class which is available in the global
+            registry.
+        renderer: A renderer class which inherits from BaseRenderer. This is used to
+            generate the images from the target view(s).
+        share_implicit_function_across_passes: If set to True
+            coarse_implicit_function is automatically set as implicit_function
+            (coarse_implicit_function=implicit_funciton). The
+            implicit_functions are then run sequentially during the rendering.
+        implicit_function_class_type: The type of implicit function to use which
+            is available in the global registry.
+        implicit_function: An instance of ImplicitFunctionBase.
+        coarse_implicit_function_class_type: The type of implicit function to use which
+            is available in the global registry.
+        coarse_implicit_function: An instance of ImplicitFunctionBase.
+            If set and `share_implicit_function_across_passes` is set to False,
+            coarse_implicit_function is instantiated on itself. It
+            is then used as the second pass during the rendering.
+            If set to None, we only do a single pass with implicit_function.
+        view_metrics: An instance of ViewMetricsBase used to compute loss terms which
+            are independent of the model's parameters.
+        view_metrics_class_type: The type of view metrics to use, must be available in
+            the global registry.
+        regularization_metrics: An instance of RegularizationMetricsBase used to compute
+            regularization terms which can depend on the model's parameters.
+        regularization_metrics_class_type: The type of regularization metrics to use,
+            must be available in the global registry.
+        loss_weights: A dictionary with a {loss_name: weight} mapping; see documentation
+            for `ViewMetrics` class for available loss functions.
+        log_vars: A list of variable names which should be logged.
+            The names should correspond to a subset of the keys of the
+            dict `preds` output by the `forward` function.
+    """  # noqa: B950
+
+    mask_images: bool = True
+    mask_depths: bool = True
+    render_image_width: int = 400
+    render_image_height: int = 400
+    mask_threshold: float = 0.5
+    output_rasterized_mc: bool = False
+    bg_color: Tuple[float, float, float] = (0.0, 0.0, 0.0)
+    chunk_size_grid: int = 4096
+    render_features_dimensions: int = 3
+    tqdm_trigger_threshold: int = 16
+
+    n_train_target_views: int = 1
+    sampling_mode_training: str = "mask_sample"
+    sampling_mode_evaluation: str = "full_grid"
+
+    # ---- global encoder settings
+    global_encoder_class_type: Optional[str] = None
+    global_encoder: Optional[GlobalEncoderBase]
+
+    # ---- raysampler
+    raysampler_class_type: str = "AdaptiveRaySampler"
+    raysampler: RaySamplerBase
+
+    # ---- renderer configs
+    renderer_class_type: str = "MultiPassEmissionAbsorptionRenderer"
+    renderer: BaseRenderer
+
+    # ---- implicit function settings
+    share_implicit_function_across_passes: bool = False
+    implicit_function_class_type: str = "NeuralRadianceFieldImplicitFunction"
+    implicit_function: ImplicitFunctionBase
+    coarse_implicit_function_class_type: Optional[str] = None
+    coarse_implicit_function: Optional[ImplicitFunctionBase]
+
+    # ----- metrics
+    view_metrics: ViewMetricsBase
+    view_metrics_class_type: str = "ViewMetrics"
+
+    regularization_metrics: RegularizationMetricsBase
+    regularization_metrics_class_type: str = "RegularizationMetrics"
+
+    # ---- loss weights
+    loss_weights: Dict[str, float] = field(
+        default_factory=lambda: {
+            "loss_rgb_mse": 1.0,
+            "loss_prev_stage_rgb_mse": 1.0,
+            "loss_mask_bce": 0.0,
+            "loss_prev_stage_mask_bce": 0.0,
+        }
+    )
+
+    # ---- variables to be logged (logger automatically ignores if not computed)
+    log_vars: List[str] = field(
+        default_factory=lambda: [
+            "loss_rgb_psnr_fg",
+            "loss_rgb_psnr",
+            "loss_rgb_mse",
+            "loss_rgb_huber",
+            "loss_depth_abs",
+            "loss_depth_abs_fg",
+            "loss_mask_neg_iou",
+            "loss_mask_bce",
+            "loss_mask_beta_prior",
+            "loss_eikonal",
+            "loss_density_tv",
+            "loss_depth_neg_penalty",
+            "loss_autodecoder_norm",
+            # metrics that are only logged in 2+stage renderes
+            "loss_prev_stage_rgb_mse",
+            "loss_prev_stage_rgb_psnr_fg",
+            "loss_prev_stage_rgb_psnr",
+            "loss_prev_stage_mask_bce",
+            # basic metrics
+            "objective",
+            "epoch",
+            "sec/it",
+        ]
+    )
+
+    def __post_init__(self):
+        # The attribute will be filled by run_auto_creation
+        run_auto_creation(self)
+        log_loss_weights(self.loss_weights, logger)
+        # We need to set it here since run_auto_creation
+        # will create coarse_implicit_function before implicit_function
+        if self.share_implicit_function_across_passes:
+            self.coarse_implicit_function = self.implicit_function
+
+    def forward(
+        self,
+        *,  # force keyword-only arguments
+        image_rgb: Optional[torch.Tensor],
+        camera: CamerasBase,
+        fg_probability: Optional[torch.Tensor] = None,
+        mask_crop: Optional[torch.Tensor] = None,
+        depth_map: Optional[torch.Tensor] = None,
+        sequence_name: Optional[List[str]] = None,
+        frame_timestamp: Optional[torch.Tensor] = None,
+        evaluation_mode: EvaluationMode = EvaluationMode.EVALUATION,
+        **kwargs,
+    ) -> Dict[str, Any]:
+        """
+        Args:
+            image_rgb: A tensor of shape `(B, 3, H, W)` containing a batch of rgb images;
+                the first `min(B, n_train_target_views)` images are considered targets and
+                are used to supervise the renders; the rest corresponding to the source
+                viewpoints from which features will be extracted.
+            camera: An instance of CamerasBase containing a batch of `B` cameras corresponding
+                to the viewpoints of target images, from which the rays will be sampled,
+                and source images, which will be used for intersecting with target rays.
+            fg_probability: A tensor of shape `(B, 1, H, W)` containing a batch of
+                foreground masks.
+            mask_crop: A binary tensor of shape `(B, 1, H, W)` deonting valid
+                regions in the input images (i.e. regions that do not correspond
+                to, e.g., zero-padding). When the `RaySampler`'s sampling mode is set to
+                "mask_sample", rays  will be sampled in the non zero regions.
+            depth_map: A tensor of shape `(B, 1, H, W)` containing a batch of depth maps.
+            sequence_name: A list of `B` strings corresponding to the sequence names
+                from which images `image_rgb` were extracted. They are used to match
+                target frames with relevant source frames.
+            frame_timestamp: Optionally a tensor of shape `(B,)` containing a batch
+                of frame timestamps.
+            evaluation_mode: one of EvaluationMode.TRAINING or
+                EvaluationMode.EVALUATION which determines the settings used for
+                rendering.
+
+        Returns:
+            preds: A dictionary containing all outputs of the forward pass including the
+                rendered images, depths, masks, losses and other metrics.
+        """
+        image_rgb, fg_probability, depth_map = preprocess_input(
+            image_rgb,
+            fg_probability,
+            depth_map,
+            self.mask_images,
+            self.mask_depths,
+            self.mask_threshold,
+            self.bg_color,
+        )
+
+        # Determine the used ray sampling mode.
+        sampling_mode = RenderSamplingMode(
+            self.sampling_mode_training
+            if evaluation_mode == EvaluationMode.TRAINING
+            else self.sampling_mode_evaluation
+        )
+
+        # (1) Sample rendering rays with the ray sampler.
+        # pyre-ignore[29]
+        ray_bundle: ImplicitronRayBundle = self.raysampler(
+            camera,
+            evaluation_mode,
+            mask=mask_crop
+            if mask_crop is not None and sampling_mode == RenderSamplingMode.MASK_SAMPLE
+            else None,
+        )
+
+        inputs_to_be_chunked = {}
+        if fg_probability is not None and self.renderer.requires_object_mask():
+            sampled_fb_prob = rend_utils.ndc_grid_sample(
+                fg_probability, ray_bundle.xys, mode="nearest"
+            )
+            inputs_to_be_chunked["object_mask"] = sampled_fb_prob > 0.5
+
+        # (2)-(3) Implicit function evaluation and Rendering
+        implicit_functions: List[Union[Callable, ImplicitFunctionBase]] = [
+            self.implicit_function
+        ]
+        if self.coarse_implicit_function is not None:
+            implicit_functions += [self.coarse_implicit_function]
+
+        if self.global_encoder is not None:
+            global_code = self.global_encoder(  # pyre-fixme[29]
+                sequence_name=sequence_name,
+                frame_timestamp=frame_timestamp,
+            )
+            implicit_functions = [
+                functools.partial(implicit_function, global_code=global_code)
+                if isinstance(implicit_function, Callable)
+                else functools.partial(
+                    implicit_function.forward, global_code=global_code
+                )
+                for implicit_function in implicit_functions
+            ]
+        rendered = self._render(
+            ray_bundle=ray_bundle,
+            sampling_mode=sampling_mode,
+            evaluation_mode=evaluation_mode,
+            implicit_functions=implicit_functions,
+            inputs_to_be_chunked=inputs_to_be_chunked,
+        )
+
+        # A dict to store losses as well as rendering results.
+        preds: Dict[str, Any] = self.view_metrics(
+            results={},
+            raymarched=rendered,
+            ray_bundle=ray_bundle,
+            image_rgb=image_rgb,
+            depth_map=depth_map,
+            fg_probability=fg_probability,
+            mask_crop=mask_crop,
+        )
+
+        preds.update(
+            self.regularization_metrics(
+                results=preds,
+                model=self,
+            )
+        )
+
+        if sampling_mode == RenderSamplingMode.MASK_SAMPLE:
+            if self.output_rasterized_mc:
+                # Visualize the monte-carlo pixel renders by splatting onto
+                # an image grid.
+                (
+                    preds["images_render"],
+                    preds["depths_render"],
+                    preds["masks_render"],
+                ) = rasterize_sparse_ray_bundle(
+                    ray_bundle,
+                    rendered.features,
+                    (self.render_image_height, self.render_image_width),
+                    rendered.depths,
+                    masks=rendered.masks,
+                )
+        elif sampling_mode == RenderSamplingMode.FULL_GRID:
+            preds["images_render"] = rendered.features.permute(0, 3, 1, 2)
+            preds["depths_render"] = rendered.depths.permute(0, 3, 1, 2)
+            preds["masks_render"] = rendered.masks.permute(0, 3, 1, 2)
+
+            preds["implicitron_render"] = ImplicitronRender(
+                image_render=preds["images_render"],
+                depth_render=preds["depths_render"],
+                mask_render=preds["masks_render"],
+            )
+        else:
+            raise AssertionError("Unreachable state")
+
+        # (4) Compute losses
+        # finally get the optimization objective using self.loss_weights
+        objective = self._get_objective(preds)
+        if objective is not None:
+            preds["objective"] = objective
+
+        return preds
+
+    def _get_objective(self, preds: Dict[str, torch.Tensor]) -> Optional[torch.Tensor]:
+        """
+        A helper function to compute the overall loss as the dot product
+        of individual loss functions with the corresponding weights.
+        """
+        return weighted_sum_losses(preds, self.loss_weights)
+
+    def visualize(
+        self,
+        viz: Optional["Visdom"],
+        visdom_env_imgs: str,
+        preds: Dict[str, Any],
+        prefix: str,
+    ) -> None:
+        """
+        Helper function to visualize the predictions generated
+        in the forward pass.
+
+        Args:
+            viz: Visdom connection object
+            visdom_env_imgs: name of visdom environment for the images.
+            preds: predictions dict like returned by forward()
+            prefix: prepended to the names of images
+        """
+        if viz is None or not viz.check_connection():
+            logger.info("no visdom server! -> skipping batch vis")
+            return
+
+        idx_image = 0
+        title = f"{prefix}_im{idx_image}"
+
+        vis_utils.visualize_basics(viz, preds, visdom_env_imgs, title=title)
+
+    def _render(
+        self,
+        *,
+        ray_bundle: ImplicitronRayBundle,
+        inputs_to_be_chunked: Dict[str, torch.Tensor],
+        sampling_mode: RenderSamplingMode,
+        **kwargs,
+    ) -> RendererOutput:
+        """
+        Args:
+            ray_bundle: A `ImplicitronRayBundle` object containing the parametrizations of the
+                sampled rendering rays.
+            inputs_to_be_chunked: A collection of tensor of shape `(B, _, H, W)`. E.g.
+                SignedDistanceFunctionRenderer requires "object_mask", shape
+                (B, 1, H, W), the silhouette of the object in the image. When
+                chunking, they are passed to the renderer as shape
+                `(B, _, chunksize)`.
+            sampling_mode: The sampling method to use. Must be a value from the
+                RenderSamplingMode Enum.
+
+        Returns:
+            An instance of RendererOutput
+        """
+        if sampling_mode == RenderSamplingMode.FULL_GRID and self.chunk_size_grid > 0:
+            return apply_chunked(
+                self.renderer,
+                chunk_generator(
+                    self.chunk_size_grid,
+                    ray_bundle,
+                    inputs_to_be_chunked,
+                    self.tqdm_trigger_threshold,
+                    **kwargs,
+                ),
+                lambda batch: torch.cat(batch, dim=1).reshape(
+                    *ray_bundle.lengths.shape[:-1], -1
+                ),
+            )
+        else:
+            # pyre-fixme[29]: `BaseRenderer` is not a function.
+            return self.renderer(
+                ray_bundle=ray_bundle,
+                **inputs_to_be_chunked,
+                **kwargs,
+            )
+
+    @classmethod
+    def raysampler_tweak_args(cls, type, args: DictConfig) -> None:
+        """
+        We don't expose certain fields of the raysampler because we want to set
+        them from our own members.
+        """
+        del args["sampling_mode_training"]
+        del args["sampling_mode_evaluation"]
+        del args["image_width"]
+        del args["image_height"]
+
+    def create_raysampler(self):
+        extra_args = {
+            "sampling_mode_training": self.sampling_mode_training,
+            "sampling_mode_evaluation": self.sampling_mode_evaluation,
+            "image_width": self.render_image_width,
+            "image_height": self.render_image_height,
+        }
+        raysampler_args = getattr(
+            self, "raysampler_" + self.raysampler_class_type + "_args"
+        )
+        self.raysampler = registry.get(RaySamplerBase, self.raysampler_class_type)(
+            **raysampler_args, **extra_args
+        )
+
+    @classmethod
+    def renderer_tweak_args(cls, type, args: DictConfig) -> None:
+        """
+        We don't expose certain fields of the renderer because we want to set
+        them based on other inputs.
+        """
+        args.pop("render_features_dimensions", None)
+        args.pop("object_bounding_sphere", None)
+
+    def create_renderer(self):
+        extra_args = {}
+
+        if self.renderer_class_type == "SignedDistanceFunctionRenderer":
+            extra_args["render_features_dimensions"] = self.render_features_dimensions
+            if not hasattr(self.raysampler, "scene_extent"):
+                raise ValueError(
+                    "SignedDistanceFunctionRenderer requires"
+                    + " a raysampler that defines the 'scene_extent' field"
+                    + " (this field is supported by, e.g., the adaptive raysampler - "
+                    + " self.raysampler_class_type='AdaptiveRaySampler')."
+                )
+            extra_args["object_bounding_sphere"] = self.raysampler.scene_extent
+
+        renderer_args = getattr(self, "renderer_" + self.renderer_class_type + "_args")
+        self.renderer = registry.get(BaseRenderer, self.renderer_class_type)(
+            **renderer_args, **extra_args
+        )
+
+    @classmethod
+    def implicit_function_tweak_args(cls, type, args: DictConfig) -> None:
+        """
+        We don't expose certain implicit_function fields because we want to set
+        them based on other inputs.
+        """
+        for arg in IMPLICIT_FUNCTION_ARGS_TO_REMOVE:
+            args.pop(arg, None)
+
+    @classmethod
+    def coarse_implicit_function_tweak_args(cls, type, args: DictConfig) -> None:
+        """
+        We don't expose certain implicit_function fields because we want to set
+        them based on other inputs.
+        """
+        for arg in IMPLICIT_FUNCTION_ARGS_TO_REMOVE:
+            args.pop(arg, None)
+
+    def _create_extra_args_for_implicit_function(self) -> Dict[str, Any]:
+        extra_args = {}
+        global_encoder_dim = (
+            0 if self.global_encoder is None else self.global_encoder.get_encoding_dim()
+        )
+        if self.implicit_function_class_type in (
+            "NeuralRadianceFieldImplicitFunction",
+            "NeRFormerImplicitFunction",
+        ):
+            extra_args["latent_dim"] = global_encoder_dim
+            extra_args["color_dim"] = self.render_features_dimensions
+
+        if self.implicit_function_class_type == "IdrFeatureField":
+            extra_args["feature_work_size"] = global_encoder_dim
+            extra_args["feature_vector_size"] = self.render_features_dimensions
+
+        if self.implicit_function_class_type == "SRNImplicitFunction":
+            extra_args["latent_dim"] = global_encoder_dim
+        return extra_args
+
+    def create_implicit_function(self) -> None:
+        implicit_function_type = registry.get(
+            ImplicitFunctionBase, self.implicit_function_class_type
+        )
+        expand_args_fields(implicit_function_type)
+
+        config_name = f"implicit_function_{self.implicit_function_class_type}_args"
+        config = getattr(self, config_name, None)
+        if config is None:
+            raise ValueError(f"{config_name} not present")
+
+        extra_args = self._create_extra_args_for_implicit_function()
+        self.implicit_function = implicit_function_type(**config, **extra_args)
+
+    def create_coarse_implicit_function(self) -> None:
+        # If coarse_implicit_function_class_type has been defined
+        # then we init a module based on its arguments
+        if (
+            self.coarse_implicit_function_class_type is not None
+            and not self.share_implicit_function_across_passes
+        ):
+            config_name = "coarse_implicit_function_{0}_args".format(
+                self.coarse_implicit_function_class_type
+            )
+            config = getattr(self, config_name, {})
+
+            implicit_function_type = registry.get(
+                ImplicitFunctionBase,
+                # pyre-ignore: config is None allow to check if this is None.
+                self.coarse_implicit_function_class_type,
+            )
+            expand_args_fields(implicit_function_type)
+
+            extra_args = self._create_extra_args_for_implicit_function()
+            self.coarse_implicit_function = implicit_function_type(
+                **config, **extra_args
+            )
+        elif self.share_implicit_function_across_passes:
+            # Since coarse_implicit_function is initialised before
+            # implicit_function we handle this case in the post_init.
+            pass
+        else:
+            self.coarse_implicit_function = None
--- a/pytorch3d/implicitron/models/utils.py
+++ b/pytorch3d/implicitron/models/utils.py
@ -0,0 +1,195 @@
+# Copyright (c) Meta Platforms, Inc. and affiliates.
+# All rights reserved.
+#
+# This source code is licensed under the BSD-style license found in the
+# LICENSE file in the root directory of this source tree.
+
+
+# Note: The #noqa comments below are for unused imports of pluggable implementations
+# which are part of implicitron. They ensure that the registry is prepopulated.
+
+import warnings
+from logging import Logger
+from typing import Any, Dict, Optional, Tuple
+
+import torch
+import tqdm
+from pytorch3d.common.compat import prod
+
+from pytorch3d.implicitron.models.renderer.base import ImplicitronRayBundle
+
+from pytorch3d.implicitron.tools import image_utils
+
+from pytorch3d.implicitron.tools.utils import cat_dataclass
+
+
+def preprocess_input(
+    image_rgb: Optional[torch.Tensor],
+    fg_probability: Optional[torch.Tensor],
+    depth_map: Optional[torch.Tensor],
+    mask_images: bool,
+    mask_depths: bool,
+    mask_threshold: float,
+    bg_color: Tuple[float, float, float],
+) -> Tuple[Optional[torch.Tensor], Optional[torch.Tensor], Optional[torch.Tensor]]:
+    """
+    Helper function to preprocess the input images and optional depth maps
+    to apply masking if required.
+
+    Args:
+        image_rgb: A tensor of shape `(B, 3, H, W)` containing a batch of rgb images
+            corresponding to the source viewpoints from which features will be extracted
+        fg_probability: A tensor of shape `(B, 1, H, W)` containing a batch
+            of foreground masks with values in [0, 1].
+        depth_map: A tensor of shape `(B, 1, H, W)` containing a batch of depth maps.
+        mask_images: Whether or not to mask the RGB image background given the
+            foreground mask (the `fg_probability` argument of `GenericModel.forward`)
+        mask_depths: Whether or not to mask the depth image background given the
+            foreground mask (the `fg_probability` argument of `GenericModel.forward`)
+        mask_threshold: If greater than 0.0, the foreground mask is
+            thresholded by this value before being applied to the RGB/Depth images
+        bg_color: RGB values for setting the background color of input image
+            if mask_images=True. Defaults to (0.0, 0.0, 0.0). Each renderer has its own
+            way to determine the background color of its output, unrelated to this.
+
+    Returns:
+        Modified image_rgb, fg_mask, depth_map
+    """
+    if image_rgb is not None and image_rgb.ndim == 3:
+        # The FrameData object is used for both frames and batches of frames,
+        # and a user might get this error if those were confused.
+        # Perhaps a user has a FrameData `fd` representing a single frame and
+        # wrote something like `model(**fd)` instead of
+        # `model(**fd.collate([fd]))`.
+        raise ValueError(
+            "Model received unbatched inputs. "
+            + "Perhaps they came from a FrameData which had not been collated."
+        )
+
+    fg_mask = fg_probability
+    if fg_mask is not None and mask_threshold > 0.0:
+        # threshold masks
+        warnings.warn("Thresholding masks!")
+        fg_mask = (fg_mask >= mask_threshold).type_as(fg_mask)
+
+    if mask_images and fg_mask is not None and image_rgb is not None:
+        # mask the image
+        warnings.warn("Masking images!")
+        image_rgb = image_utils.mask_background(
+            image_rgb, fg_mask, dim_color=1, bg_color=torch.tensor(bg_color)
+        )
+
+    if mask_depths and fg_mask is not None and depth_map is not None:
+        # mask the depths
+        assert (
+            mask_threshold > 0.0
+        ), "Depths should be masked only with thresholded masks"
+        warnings.warn("Masking depths!")
+        depth_map = depth_map * fg_mask
+
+    return image_rgb, fg_mask, depth_map
+
+
+def log_loss_weights(loss_weights: Dict[str, float], logger: Logger) -> None:
+    """
+    Print a table of the loss weights.
+    """
+    loss_weights_message = (
+        "-------\nloss_weights:\n"
+        + "\n".join(f"{k:40s}: {w:1.2e}" for k, w in loss_weights.items())
+        + "-------"
+    )
+    logger.info(loss_weights_message)
+
+
+def weighted_sum_losses(
+    preds: Dict[str, torch.Tensor], loss_weights: Dict[str, float]
+) -> Optional[torch.Tensor]:
+    """
+    A helper function to compute the overall loss as the dot product
+    of individual loss functions with the corresponding weights.
+    """
+    losses_weighted = [
+        preds[k] * float(w)
+        for k, w in loss_weights.items()
+        if (k in preds and w != 0.0)
+    ]
+    if len(losses_weighted) == 0:
+        warnings.warn("No main objective found.")
+        return None
+    loss = sum(losses_weighted)
+    assert torch.is_tensor(loss)
+    # pyre-fixme[7]: Expected `Optional[Tensor]` but got `int`.
+    return loss
+
+
+def apply_chunked(func, chunk_generator, tensor_collator):
+    """
+    Helper function to apply a function on a sequence of
+    chunked inputs yielded by a generator and collate
+    the result.
+    """
+    processed_chunks = [
+        func(*chunk_args, **chunk_kwargs)
+        for chunk_args, chunk_kwargs in chunk_generator
+    ]
+
+    return cat_dataclass(processed_chunks, tensor_collator)
+
+
+def chunk_generator(
+    chunk_size: int,
+    ray_bundle: ImplicitronRayBundle,
+    chunked_inputs: Dict[str, torch.Tensor],
+    tqdm_trigger_threshold: int,
+    *args,
+    **kwargs,
+):
+    """
+    Helper function which yields chunks of rays from the
+    input ray_bundle, to be used when the number of rays is
+    large and will not fit in memory for rendering.
+    """
+    (
+        batch_size,
+        *spatial_dim,
+        n_pts_per_ray,
+    ) = ray_bundle.lengths.shape  # B x ... x n_pts_per_ray
+    if n_pts_per_ray > 0 and chunk_size % n_pts_per_ray != 0:
+        raise ValueError(
+            f"chunk_size_grid ({chunk_size}) should be divisible "
+            f"by n_pts_per_ray ({n_pts_per_ray})"
+        )
+
+    n_rays = prod(spatial_dim)
+    # special handling for raytracing-based methods
+    n_chunks = -(-n_rays * max(n_pts_per_ray, 1) // chunk_size)
+    chunk_size_in_rays = -(-n_rays // n_chunks)
+
+    iter = range(0, n_rays, chunk_size_in_rays)
+    if len(iter) >= tqdm_trigger_threshold:
+        iter = tqdm.tqdm(iter)
+
+    def _safe_slice(
+        tensor: Optional[torch.Tensor], start_idx: int, end_idx: int
+    ) -> Any:
+        return tensor[start_idx:end_idx] if tensor is not None else None
+
+    for start_idx in iter:
+        end_idx = min(start_idx + chunk_size_in_rays, n_rays)
+        ray_bundle_chunk = ImplicitronRayBundle(
+            origins=ray_bundle.origins.reshape(batch_size, -1, 3)[:, start_idx:end_idx],
+            directions=ray_bundle.directions.reshape(batch_size, -1, 3)[
+                :, start_idx:end_idx
+            ],
+            lengths=ray_bundle.lengths.reshape(batch_size, n_rays, n_pts_per_ray)[
+                :, start_idx:end_idx
+            ],
+            xys=ray_bundle.xys.reshape(batch_size, -1, 2)[:, start_idx:end_idx],
+            camera_ids=_safe_slice(ray_bundle.camera_ids, start_idx, end_idx),
+            camera_counts=_safe_slice(ray_bundle.camera_counts, start_idx, end_idx),
+        )
+        extra_args = kwargs.copy()
+        for k, v in chunked_inputs.items():
+            extra_args[k] = v.flatten(2)[:, :, start_idx:end_idx]
+        yield [ray_bundle_chunk, *args], extra_args
--- a/pytorch3d/implicitron/tools/rasterize_mc.py
+++ b/pytorch3d/implicitron/tools/rasterize_mc.py
@ -7,8 +7,9 @@
 import math
 from typing import Optional, Tuple

+import pytorch3d
+
 import torch
-from pytorch3d.implicitron.models.renderer.base import ImplicitronRayBundle
 from pytorch3d.ops import packed_to_padded
 from pytorch3d.renderer import PerspectiveCameras
 from pytorch3d.structures import Pointclouds
@ -18,7 +19,7 @@ from .point_cloud_utils import render_point_cloud_pytorch3d

@torch.no_grad()
 def rasterize_sparse_ray_bundle(
-    ray_bundle: ImplicitronRayBundle,
+    ray_bundle: "pytorch3d.implicitron.models.renderer.base.ImplicitronRayBundle",
    features: torch.Tensor,
    image_size_hw: Tuple[int, int],
    depth: torch.Tensor,
--- a/tests/implicitron/models/init.py
+++ b/tests/implicitron/models/init.py
@ -0,0 +1,5 @@
+# Copyright (c) Meta Platforms, Inc. and affiliates.
+# All rights reserved.
+#
+# This source code is licensed under the BSD-style license found in the
+# LICENSE file in the root directory of this source tree.
--- a/tests/implicitron/models/test_overfit_model.py
+++ b/tests/implicitron/models/test_overfit_model.py
@ -0,0 +1,217 @@
+# Copyright (c) Meta Platforms, Inc. and affiliates.
+# All rights reserved.
+#
+# This source code is licensed under the BSD-style license found in the
+# LICENSE file in the root directory of this source tree.
+
+import unittest
+from typing import Any, Dict
+from unittest.mock import patch
+
+import torch
+from pytorch3d.implicitron.models.generic_model import GenericModel
+from pytorch3d.implicitron.models.overfit_model import OverfitModel
+from pytorch3d.implicitron.models.renderer.base import EvaluationMode
+from pytorch3d.implicitron.tools.config import expand_args_fields
+from pytorch3d.renderer.cameras import look_at_view_transform, PerspectiveCameras
+
+DEVICE = torch.device("cuda:0")
+
+
+def _generate_fake_inputs(N: int, H: int, W: int) -> Dict[str, Any]:
+    R, T = look_at_view_transform(azim=torch.rand(N) * 360)
+    return {
+        "camera": PerspectiveCameras(R=R, T=T, device=DEVICE),
+        "fg_probability": torch.randint(
+            high=2, size=(N, 1, H, W), device=DEVICE
+        ).float(),
+        "depth_map": torch.rand((N, 1, H, W), device=DEVICE) + 0.1,
+        "mask_crop": torch.randint(high=2, size=(N, 1, H, W), device=DEVICE).float(),
+        "sequence_name": ["sequence"] * N,
+        "image_rgb": torch.rand((N, 1, H, W), device=DEVICE),
+    }
+
+
+def mock_safe_multinomial(input: torch.Tensor, num_samples: int) -> torch.Tensor:
+    """Return non deterministic indexes to mock safe_multinomial
+
+    Args:
+        input: tensor of shape [B, n] containing non-negative values;
+                rows are interpreted as unnormalized event probabilities
+                in categorical distributions.
+        num_samples: number of samples to take.
+
+    Returns:
+        Tensor of shape [B, num_samples]
+    """
+    batch_size = input.shape[0]
+    return torch.arange(num_samples).repeat(batch_size, 1).to(DEVICE)
+
+
+class TestOverfitModel(unittest.TestCase):
+    def setUp(self):
+        torch.manual_seed(42)
+
+    def test_overfit_model_vs_generic_model_with_batch_size_one(self):
+        """In this test we compare OverfitModel to GenericModel behavior.
+
+        We use a Nerf setup (2 rendering passes).
+
+        OverfitModel is a specific case of GenericModel. Hence, with the same inputs,
+        they should provide the exact same results.
+        """
+        expand_args_fields(OverfitModel)
+        expand_args_fields(GenericModel)
+        batch_size, image_height, image_width = 1, 80, 80
+        assert batch_size == 1
+        overfit_model = OverfitModel(
+            render_image_height=image_height,
+            render_image_width=image_width,
+            coarse_implicit_function_class_type="NeuralRadianceFieldImplicitFunction",
+            # To avoid randomization to compare the outputs of our model
+            # we deactivate the stratified_point_sampling_training
+            raysampler_AdaptiveRaySampler_args={
+                "stratified_point_sampling_training": False
+            },
+            global_encoder_class_type="SequenceAutodecoder",
+            global_encoder_SequenceAutodecoder_args={
+                "autodecoder_args": {
+                    "n_instances": 1000,
+                    "init_scale": 1.0,
+                    "encoding_dim": 64,
+                }
+            },
+        )
+        generic_model = GenericModel(
+            render_image_height=image_height,
+            render_image_width=image_width,
+            n_train_target_views=batch_size,
+            num_passes=2,
+            # To avoid randomization to compare the outputs of our model
+            # we deactivate the stratified_point_sampling_training
+            raysampler_AdaptiveRaySampler_args={
+                "stratified_point_sampling_training": False
+            },
+            global_encoder_class_type="SequenceAutodecoder",
+            global_encoder_SequenceAutodecoder_args={
+                "autodecoder_args": {
+                    "n_instances": 1000,
+                    "init_scale": 1.0,
+                    "encoding_dim": 64,
+                }
+            },
+        )
+
+        # Check if they do share the number of parameters
+        num_params_mvm = sum(p.numel() for p in overfit_model.parameters())
+        num_params_gm = sum(p.numel() for p in generic_model.parameters())
+        self.assertEqual(num_params_mvm, num_params_gm)
+
+        # Adapt the mapping from generic model to overfit model
+        mapping_om_from_gm = {
+            key.replace("_implicit_functions.0._fn", "implicit_function").replace(
+                "_implicit_functions.1._fn", "coarse_implicit_function"
+            ): val
+            for key, val in generic_model.state_dict().items()
+        }
+        # Copy parameters from generic_model to overfit_model
+        overfit_model.load_state_dict(mapping_om_from_gm)
+
+        overfit_model.to(DEVICE)
+        generic_model.to(DEVICE)
+        inputs_ = _generate_fake_inputs(batch_size, image_height, image_width)
+
+        # training forward pass
+        overfit_model.train()
+        generic_model.train()
+
+        with patch(
+            "pytorch3d.renderer.implicit.raysampling._safe_multinomial",
+            side_effect=mock_safe_multinomial,
+        ):
+            train_preds_om = overfit_model(
+                **inputs_,
+                evaluation_mode=EvaluationMode.TRAINING,
+            )
+            train_preds_gm = generic_model(
+                **inputs_,
+                evaluation_mode=EvaluationMode.TRAINING,
+            )
+
+        self.assertTrue(len(train_preds_om) == len(train_preds_gm))
+
+        self.assertTrue(train_preds_om["objective"].isfinite().item())
+        # We avoid all the randomization and the weights are the same
+        # The objective should be the same
+        self.assertTrue(
+            torch.allclose(train_preds_om["objective"], train_preds_gm["objective"])
+        )
+
+        # Test if the evaluation works
+        overfit_model.eval()
+        generic_model.eval()
+        with torch.no_grad():
+            eval_preds_om = overfit_model(
+                **inputs_,
+                evaluation_mode=EvaluationMode.EVALUATION,
+            )
+            eval_preds_gm = generic_model(
+                **inputs_,
+                evaluation_mode=EvaluationMode.EVALUATION,
+            )
+
+        self.assertEqual(
+            eval_preds_om["images_render"].shape,
+            (batch_size, 3, image_height, image_width),
+        )
+        self.assertTrue(
+            torch.allclose(eval_preds_om["objective"], eval_preds_gm["objective"])
+        )
+        self.assertTrue(
+            torch.allclose(
+                eval_preds_om["images_render"], eval_preds_gm["images_render"]
+            )
+        )
+
+    def test_overfit_model_check_share_weights(self):
+        model = OverfitModel(share_implicit_function_across_passes=True)
+        for p1, p2 in zip(
+            model.implicit_function.parameters(),
+            model.coarse_implicit_function.parameters(),
+        ):
+            self.assertEqual(id(p1), id(p2))
+
+        model.to(DEVICE)
+        inputs_ = _generate_fake_inputs(2, 80, 80)
+        model(**inputs_, evaluation_mode=EvaluationMode.TRAINING)
+
+    def test_overfit_model_check_no_share_weights(self):
+        model = OverfitModel(
+            share_implicit_function_across_passes=False,
+            coarse_implicit_function_class_type="NeuralRadianceFieldImplicitFunction",
+            coarse_implicit_function_NeuralRadianceFieldImplicitFunction_args={
+                "transformer_dim_down_factor": 1.0,
+                "n_hidden_neurons_xyz": 256,
+                "n_layers_xyz": 8,
+                "append_xyz": (5,),
+            },
+        )
+        for p1, p2 in zip(
+            model.implicit_function.parameters(),
+            model.coarse_implicit_function.parameters(),
+        ):
+            self.assertNotEqual(id(p1), id(p2))
+
+        model.to(DEVICE)
+        inputs_ = _generate_fake_inputs(2, 80, 80)
+        model(**inputs_, evaluation_mode=EvaluationMode.TRAINING)
+
+    def test_overfit_model_coarse_implicit_function_is_none(self):
+        model = OverfitModel(
+            share_implicit_function_across_passes=False,
+            coarse_implicit_function_NeuralRadianceFieldImplicitFunction_args=None,
+        )
+        self.assertIsNone(model.coarse_implicit_function)
+        model.to(DEVICE)
+        inputs_ = _generate_fake_inputs(2, 80, 80)
+        model(**inputs_, evaluation_mode=EvaluationMode.TRAINING)
--- a/tests/implicitron/models/test_utils.py
+++ b/tests/implicitron/models/test_utils.py
@ -0,0 +1,66 @@
+# Copyright (c) Meta Platforms, Inc. and affiliates.
+# All rights reserved.
+#
+# This source code is licensed under the BSD-style license found in the
+# LICENSE file in the root directory of this source tree.
+
+
+import unittest
+
+import torch
+
+from pytorch3d.implicitron.models.utils import preprocess_input, weighted_sum_losses
+
+
+class TestUtils(unittest.TestCase):
+    def test_prepare_inputs_wrong_num_dim(self):
+        img = torch.randn(3, 3, 3)
+        with self.assertRaises(ValueError) as context:
+            img, fg_prob, depth_map = preprocess_input(
+                img, None, None, True, True, 0.5, (0.0, 0.0, 0.0)
+            )
+            self.assertEqual(
+                "Model received unbatched inputs. "
+                + "Perhaps they came from a FrameData which had not been collated.",
+                context.exception,
+            )
+
+    def test_prepare_inputs_mask_image_true(self):
+        batch, channels, height, width = 2, 3, 10, 10
+        img = torch.ones(batch, channels, height, width)
+        # Create a mask on the lower triangular matrix
+        fg_prob = torch.tril(torch.ones(batch, 1, height, width)) * 0.3
+
+        out_img, out_fg_prob, out_depth_map = preprocess_input(
+            img, fg_prob, None, True, False, 0.3, (0.0, 0.0, 0.0)
+        )
+
+        self.assertTrue(torch.equal(out_img, torch.tril(img)))
+        self.assertTrue(torch.equal(out_fg_prob, fg_prob >= 0.3))
+        self.assertIsNone(out_depth_map)
+
+    def test_prepare_inputs_mask_depth_true(self):
+        batch, channels, height, width = 2, 3, 10, 10
+        img = torch.ones(batch, channels, height, width)
+        depth_map = torch.randn(batch, channels, height, width)
+        # Create a mask on the lower triangular matrix
+        fg_prob = torch.tril(torch.ones(batch, 1, height, width)) * 0.3
+
+        out_img, out_fg_prob, out_depth_map = preprocess_input(
+            img, fg_prob, depth_map, False, True, 0.3, (0.0, 0.0, 0.0)
+        )
+
+        self.assertTrue(torch.equal(out_img, img))
+        self.assertTrue(torch.equal(out_fg_prob, fg_prob >= 0.3))
+        self.assertTrue(torch.equal(out_depth_map, torch.tril(depth_map)))
+
+    def test_weighted_sum_losses(self):
+        preds = {"a": torch.tensor(2), "b": torch.tensor(2)}
+        weights = {"a": 2.0, "b": 0.0}
+        loss = weighted_sum_losses(preds, weights)
+        self.assertEqual(loss, 4.0)
+
+    def test_weighted_sum_losses_raise_warning(self):
+        preds = {"a": torch.tensor(2), "b": torch.tensor(2)}
+        weights = {"c": 2.0, "d": 2.0}
+        self.assertIsNone(weighted_sum_losses(preds, weights))