GitLab

Summary:
Although we can load per-vertex normals in `load_obj`, saving per-vertex normals is not supported in `save_obj`.

This patch fixes this by allowing passing per-vertex normal data in `save_obj`:
``` python
def save_obj(
    f: PathOrStr,
    verts,
    faces,
    decimal_places: Optional[int] = None,
    path_manager: Optional[PathManager] = None,
    *,
    verts_normals: Optional[torch.Tensor] = None,
    faces_normals: Optional[torch.Tensor] = None,
    verts_uvs: Optional[torch.Tensor] = None,
    faces_uvs: Optional[torch.Tensor] = None,
    texture_map: Optional[torch.Tensor] = None,
) -> None:
    """
    Save a mesh to an .obj file.

    Args:
        f: File (str or path) to which the mesh should be written.
        verts: FloatTensor of shape (V, 3) giving vertex coordinates.
        faces: LongTensor of shape (F, 3) giving faces.
        decimal_places: Number of decimal places for saving.
        path_manager: Optional PathManager for interpreting f if
            it is a str.
        verts_normals: FloatTensor of shape (V, 3) giving the normal per vertex.
        faces_normals: LongTensor of shape (F, 3) giving the index into verts_normals
            for each vertex in the face.
        verts_uvs: FloatTensor of shape (V, 2) giving the uv coordinate per vertex.
        faces_uvs: LongTensor of shape (F, 3) giving the index into verts_uvs for
            each vertex in the face.
        texture_map: FloatTensor of shape (H, W, 3) representing the texture map
            for the mesh which will be saved as an image. The values are expected
            to be in the range [0, 1],
    """
```

Pull Request resolved: https://github.com/facebookresearch/pytorch3d/pull/1511

Reviewed By: shapovalov

Differential Revision: D45086045

Pulled By: bottler

fbshipit-source-id: 666efb0d2c302df6cf9f2f6601d83a07856bf32f