Texturing API updates

Summary:
A fairly big refactor of the texturing API with some breaking changes to how textures are defined.

Main changes:
- There are now 3 types of texture classes: `TexturesUV`, `TexturesAtlas` and `TexturesVertex`. Each class:
   - has a `sample_textures` function which accepts the `fragments` from rasterization and returns `texels`. This means that the shaders will not need to know the type of the mesh texture which will resolve several issues people were reporting on GitHub.
  -  has a `join_batch` method for joining multiple textures of the same type into a batch

Reviewed By: gkioxari

Differential Revision: D21067427

fbshipit-source-id: 4b346500a60181e72fdd1b0dd89b5505c7a33926

docs/tutorials/camera_position_optimization_with_differentiable_rendering.ipynb

@@ -520,6 +520,9 @@
  ],
  "metadata": {
   "accelerator": "GPU",
+  "anp_metadata": {
+   "path": "fbsource/fbcode/vision/fair/pytorch3d/docs/tutorials/camera_position_optimization_with_differentiable_rendering.ipynb"
+  },
   "bento_stylesheets": {
    "bento/extensions/flow/main.css": true,
    "bento/extensions/kernel_selector/main.css": true,
@@ -533,6 +536,9 @@
    "provenance": [],
    "toc_visible": true
   },
+  "disseminate_notebook_info": {
+   "backup_notebook_id": "1062179640844868"
+  },
   "kernelspec": {
    "display_name": "pytorch3d (local)",
    "language": "python",

docs/tutorials/render_textured_meshes.ipynb

@@ -84,7 +84,7 @@
     "from skimage.io import imread\n",
     "\n",
     "# Util function for loading meshes\n",
-    "from pytorch3d.io import load_objs_as_meshes\n",
+    "from pytorch3d.io import load_objs_as_meshes, load_obj\n",
     "\n",
     "# Data structures and functions for rendering\n",
     "from pytorch3d.structures import Meshes, Textures\n",
@@ -97,7 +97,7 @@
     "    RasterizationSettings, \n",
     "    MeshRenderer, \n",
     "    MeshRasterizer,  \n",
-    "    TexturedSoftPhongShader\n",
+    "    SoftPhongShader\n",
     ")\n",
     "\n",
     "# add path for demo utils functions \n",
@@ -316,7 +316,7 @@
     "        cameras=cameras, \n",
     "        raster_settings=raster_settings\n",
     "    ),\n",
-    "    shader=TexturedSoftPhongShader(\n",
+    "    shader=SoftPhongShader(\n",
     "        device=device, \n",
     "        cameras=cameras,\n",
     "        lights=lights\n",
@@ -563,6 +563,9 @@
  ],
  "metadata": {
   "accelerator": "GPU",
+  "anp_metadata": {
+   "path": "fbsource/fbcode/vision/fair/pytorch3d/docs/tutorials/render_textured_meshes.ipynb"
+  },
   "bento_stylesheets": {
    "bento/extensions/flow/main.css": true,
    "bento/extensions/kernel_selector/main.css": true,
@@ -575,6 +578,9 @@
    "name": "render_textured_meshes.ipynb",
    "provenance": []
   },
+  "disseminate_notebook_info": {
+   "backup_notebook_id": "569222367081034"
+  },
   "kernelspec": {
    "display_name": "pytorch3d (local)",
    "language": "python",