Adding the option to choose the texture sampling mode in TexturesUV.

Summary:
This diff adds the `sample_mode` parameter to `TexturesUV` to control the interpolation mode during texture sampling. It simply gets forwarded to `torch.nn.funcitonal.grid_sample`.

This option was requested in this [GitHub issue](#805).

Reviewed By: patricklabatut

Differential Revision: D32665185

fbshipit-source-id: ac0bc66a018bd4cb20d75fec2d7c11145dd20199

Author: anadodik

pytorch3d/renderer/mesh/textures.py

@@ -596,6 +596,7 @@ def __init__(
         verts_uvs: Union[torch.Tensor, List[torch.Tensor], Tuple[torch.Tensor]],
         padding_mode: str = "border",
         align_corners: bool = True,
+        sampling_mode: str = "bilinear",
     ) -> None:
         """
         Textures are represented as a per mesh texture map and uv coordinates for each
@@ -613,6 +614,9 @@ def __init__(
                             indicate the centers of the edge pixels in the maps.
             padding_mode: padding mode for outside grid values
                                 ("zeros", "border" or "reflection").
+            sampling_mode: type of interpolation used to sample the texture.
+                            Corresponds to the mode parameter in PyTorch's
+                            grid_sample ("nearest" or "bilinear").
 
         The align_corners and padding_mode arguments correspond to the arguments
         of the `grid_sample` torch function. There is an informative illustration of
@@ -641,6 +645,7 @@ def __init__(
         """
         self.padding_mode = padding_mode
         self.align_corners = align_corners
+        self.sampling_mode = sampling_mode
         if isinstance(faces_uvs, (list, tuple)):
             for fv in faces_uvs:
                 if fv.ndim != 2 or fv.shape[-1] != 3:
@@ -749,6 +754,9 @@ def clone(self) -> "TexturesUV":
             self.maps_padded().clone(),
             self.faces_uvs_padded().clone(),
             self.verts_uvs_padded().clone(),
+            align_corners=self.align_corners,
+            padding_mode=self.padding_mode,
+            sampling_mode=self.sampling_mode,
         )
         if self._maps_list is not None:
             tex._maps_list = [m.clone() for m in self._maps_list]
@@ -770,6 +778,9 @@ def detach(self) -> "TexturesUV":
             self.maps_padded().detach(),
             self.faces_uvs_padded().detach(),
             self.verts_uvs_padded().detach(),
+            align_corners=self.align_corners,
+            padding_mode=self.padding_mode,
+            sampling_mode=self.sampling_mode,
         )
         if self._maps_list is not None:
             tex._maps_list = [m.detach() for m in self._maps_list]
@@ -801,6 +812,7 @@ def __getitem__(self, index) -> "TexturesUV":
                 maps=maps,
                 padding_mode=self.padding_mode,
                 align_corners=self.align_corners,
+                sampling_mode=self.sampling_mode,
             )
         elif all(torch.is_tensor(f) for f in [faces_uvs, verts_uvs, maps]):
             new_tex = self.__class__(
@@ -809,6 +821,7 @@ def __getitem__(self, index) -> "TexturesUV":
                 maps=[maps],
                 padding_mode=self.padding_mode,
                 align_corners=self.align_corners,
+                sampling_mode=self.sampling_mode,
             )
         else:
             raise ValueError("Not all values are provided in the correct format")
@@ -889,6 +902,7 @@ def extend(self, N: int) -> "TexturesUV":
             verts_uvs=new_props["verts_uvs_padded"],
             padding_mode=self.padding_mode,
             align_corners=self.align_corners,
+            sampling_mode=self.sampling_mode,
         )
 
         new_tex._num_faces_per_mesh = new_props["_num_faces_per_mesh"]
@@ -966,6 +980,7 @@ def sample_textures(self, fragments, **kwargs) -> torch.Tensor:
         texels = F.grid_sample(
             texture_maps,
             pixel_uvs,
+            mode=self.sampling_mode,
             align_corners=self.align_corners,
             padding_mode=self.padding_mode,
         )
@@ -1003,6 +1018,7 @@ def faces_verts_textures_packed(self) -> torch.Tensor:
         textures = F.grid_sample(
             texture_maps,
             faces_verts_uvs,
+            mode=self.sampling_mode,
             align_corners=self.align_corners,
             padding_mode=self.padding_mode,
         )  # NxCxmax(Fi)x3
@@ -1060,6 +1076,7 @@ def join_batch(self, textures: List["TexturesUV"]) -> "TexturesUV":
             faces_uvs=faces_uvs_list,
             padding_mode=self.padding_mode,
             align_corners=self.align_corners,
+            sampling_mode=self.sampling_mode,
         )
         new_tex._num_faces_per_mesh = num_faces_per_mesh
         return new_tex
@@ -1227,6 +1244,7 @@ def join_scene(self) -> "TexturesUV":
             faces_uvs=[torch.cat(faces_uvs_merged)],
             align_corners=self.align_corners,
             padding_mode=self.padding_mode,
+            sampling_mode=self.sampling_mode,
         )
 
     def centers_for_image(self, index: int) -> torch.Tensor:
@@ -1259,6 +1277,7 @@ def centers_for_image(self, index: int) -> torch.Tensor:
                 torch.flip(coords.to(texture_image), [2]),
                 # Convert from [0, 1] -> [-1, 1] range expected by grid sample
                 verts_uvs[:, None] * 2.0 - 1,
+                mode=self.sampling_mode,
                 align_corners=self.align_corners,
                 padding_mode=self.padding_mode,
             ).cpu()