Bug fix for case where aspect ratio is a float

Summary:
- Fix the calculation of the non square NDC range when the H and W are not integer multiples.
- Add test for this case

Reviewed By: gkioxari

Differential Revision: D26613213

fbshipit-source-id: df6763cac602e9f1d516b41b432c4d2cfbaa356d

pytorch3d/csrc/rasterize_points/rasterization_utils.cuh

@@ -10,7 +10,9 @@
 __device__ inline float NonSquareNdcRange(int S1, int S2) {
   float range = 2.0f;
   if (S1 > S2) {
-    range = ((S1 / S2) * range);
+    // First multiply S1 by float range so that division results
+    // in a float value.
+    range = (S1 * range) / S2;
   }
   return range;
 }

pytorch3d/csrc/rasterize_points/rasterization_utils.h

@@ -10,7 +10,7 @@
 inline float NonSquareNdcRange(int S1, int S2) {
   float range = 2.0f;
   if (S1 > S2) {
-    range = ((S1 / S2) * range);
+    range = (S1 * range) / S2;
   }
   return range;
 }