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Texture Atlas sampling bug fix

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Summary: Fixes the index out of bound errors for texture sampling from a texture atlas: when barycentric coordinates are 1.0, the integer index into the (R, R) per face texture map is R (max can only be R-1).

Reviewed By: gkioxari

Differential Revision: D25543803

fbshipit-source-id: 82d0935b981352b49c1d95d5a17f9cc88bad0a82
This commit is contained in:
Nikhila Ravi
2020-12-17 04:09:40 -08:00
committed by Facebook GitHub Bot
parent 3d769a66cb
commit 01759d8ffb
3 changed files with 58 additions and 8 deletions
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docs/notes/renderer_getting_started.md
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@@ -84,7 +84,8 @@ For mesh texturing we offer several options (in `pytorch3d/renderer/mesh/texturi
1. **Vertex Textures**: D dimensional textures for each vertex (for example an RGB color) which can be interpolated across the face. This can be represented as an `(N, V, D)` tensor. This is a fairly simple representation though and cannot model complex textures if the mesh faces are large.
2. **UV Textures**: vertex UV coordinates and **one** texture map for the whole mesh. For a point on a face with given barycentric coordinates, the face color can be computed by interpolating the vertex uv coordinates and then sampling from the texture map. This representation requires two tensors (UVs: `(N, V, 2), Texture map: `(N, H, W, 3)`), and is limited to only support one texture map per mesh.
3. **Face Textures**: In more complex cases such as ShapeNet meshes, there are multiple texture maps per mesh and some faces have texture while other do not. For these cases, a more flexible representation is a texture atlas, where each face is represented as an `(RxR)` texture map where R is the texture resolution. For a given point on the face, the texture value can be sampled from the per face texture map using the barycentric coordinates of the point. This representation requires one tensor of shape `(N, F, R, R, 3)`. This texturing method is inspired by the SoftRasterizer implementation. For more details refer to the [`make_material_atlas`](https://github.com/facebookresearch/pytorch3d/blob/master/pytorch3d/io/mtl_io.py#L123) and [`sample_textures`](https://github.com/facebookresearch/pytorch3d/blob/master/pytorch3d/renderer/mesh/textures.py#L452) functions.
3. **Face Textures**: In more complex cases such as ShapeNet meshes, there are multiple texture maps per mesh and some faces have texture while other do not. For these cases, a more flexible representation is a texture atlas, where each face is represented as an `(RxR)` texture map where R is the texture resolution. For a given point on the face, the texture value can be sampled from the per face texture map using the barycentric coordinates of the point. This representation requires one tensor of shape `(N, F, R, R, 3)`. This texturing method is inspired by the SoftRasterizer implementation. For more details refer to the [`make_material_atlas`](https://github.com/facebookresearch/pytorch3d/blob/master/pytorch3d/io/mtl_io.py#L123) and [`sample_textures`](https://github.com/facebookresearch/pytorch3d/blob/master/pytorch3d/renderer/mesh/textures.py#L452) functions. **NOTE:**: The `TextureAtlas` texture sampling is only differentiable with respect to the texture atlas but not differentiable with respect to the barycentric coordinates.
<img src="assets/texturing.jpg" width="1000">