reallow scalar background color for point rendering

Summary: A scalar background color is not meant to be allowed for the point renderer. It used to be ignored with a warning, but a recent code change made it an error. It was being used, at least in the black (value=0.0) case. Re-enable it.

Reviewed By: nikhilaravi

Differential Revision: D34519651

fbshipit-source-id: d37dcf145bb7b8999c9265cf8fc39b084059dd18

pytorch3d/renderer/points/compositor.py

@@ -4,7 +4,6 @@
 # This source code is licensed under the BSD-style license found in the
 # LICENSE file in the root directory of this source tree.
 
-import warnings
 from typing import List, Optional, Tuple, Union
 
 import torch
@@ -85,7 +84,10 @@ def _add_background_color_to_images(pix_idxs, images, background_color):
     if not torch.is_tensor(background_color):
         background_color = images.new_tensor(background_color)
 
-    if len(background_color.shape) != 1:
+    if background_color.ndim == 0:
+        background_color = background_color.expand(images.shape[1])
+
+    if background_color.ndim > 1:
         raise ValueError("Wrong shape of background_color")
 
     background_color = background_color.to(images)
@@ -98,7 +100,8 @@ def _add_background_color_to_images(pix_idxs, images, background_color):
 
     if images.shape[1] != background_color.shape[0]:
         raise ValueError(
-            f"background color has {background_color.shape[0] } channels not {images.shape[1]}"
+            "Background color has %s channels not %s"
+            % (background_color.shape[0], images.shape[1])
         )
 
     num_background_pixels = background_mask.sum()