Change default settings of clip_barycentric_coords

Summary: When raster_settings.clip_barycentric_coords is unspecified, clip_barycentric_coords is turned on if blur_radius is greater than 0.  This matches the behavior prior to D21705503 (https://github.com/facebookresearch/pytorch3d/commit/cc70950f4064e3feeb55281b829aa55aa4a7e942).

Reviewed By: gkioxari

Differential Revision: D23375257

fbshipit-source-id: 4b87588aabb69d4d835d4dcceb11153628121d30

pytorch3d/renderer/mesh/rasterizer.py

@@ -37,7 +37,7 @@ class RasterizationSettings:
         bin_size: Optional[int] = None,
         max_faces_per_bin: Optional[int] = None,
         perspective_correct: bool = False,
-        clip_barycentric_coords: bool = False,
+        clip_barycentric_coords: Optional[bool] = None,
         cull_backfaces: bool = False,
     ):
         self.image_size = image_size
@@ -125,6 +125,14 @@ class MeshRasterizer(nn.Module):
         """
         meshes_screen = self.transform(meshes_world, **kwargs)
         raster_settings = kwargs.get("raster_settings", self.raster_settings)
+
+        # By default, turn on clip_barycentric_coords if blur_radius > 0.
+        # When blur_radius > 0, a face can be matched to a pixel that is outside the
+        # face, resulting in negative barycentric coordinates.
+        clip_barycentric_coords = raster_settings.clip_barycentric_coords
+        if clip_barycentric_coords is None:
+            clip_barycentric_coords = raster_settings.blur_radius > 0.0
+
         # TODO(jcjohns): Should we try to set perspective_correct automatically
         # based on the type of the camera?
         pix_to_face, zbuf, bary_coords, dists = rasterize_meshes(
@@ -135,7 +143,7 @@ class MeshRasterizer(nn.Module):
             bin_size=raster_settings.bin_size,
             max_faces_per_bin=raster_settings.max_faces_per_bin,
             perspective_correct=raster_settings.perspective_correct,
-            clip_barycentric_coords=raster_settings.clip_barycentric_coords,
+            clip_barycentric_coords=clip_barycentric_coords,
             cull_backfaces=raster_settings.cull_backfaces,
         )
         return Fragments(