fix pts scale, save ply

Summary:
Fix:
* Scaling of point clouds for scalars
* save_ply compatible cat

Reviewed By: nikhilaravi

Differential Revision: D22298609

fbshipit-source-id: abe94a5b64baf325587202d20adfc36912cc1478

pytorch3d/io/ply_io.py

@@ -783,7 +783,11 @@ def save_ply(
         decimal_places: Number of decimal places for saving.
     """
 
-    verts_normals = torch.FloatTensor([]) if verts_normals is None else verts_normals
+    verts_normals = (
+        torch.tensor([], dtype=torch.float32, device=verts.device)
+        if verts_normals is None
+        else verts_normals
+    )
     faces = torch.LongTensor([]) if faces is None else faces
 
     if len(verts) and not (verts.dim() == 2 and verts.size(1) == 3):

pytorch3d/structures/pointclouds.py

@@ -511,7 +511,6 @@ class Pointclouds(object):
         Returns:
             1D tensor of indices.
         """
-        self._compute_packed()
         if self._padded_to_packed_idx is not None:
             return self._padded_to_packed_idx
         if self._N == 0:
@@ -520,7 +519,7 @@ class Pointclouds(object):
             self._padded_to_packed_idx = torch.cat(
                 [
                     torch.arange(v, dtype=torch.int64, device=self.device) + i * self._P
-                    for (i, v) in enumerate(self._num_points_per_cloud)
+                    for (i, v) in enumerate(self.num_points_per_cloud())
                 ],
                 dim=0,
             )
@@ -797,7 +796,7 @@ class Pointclouds(object):
             self.
         """
         if not torch.is_tensor(scale):
-            scale = torch.full(len(self), scale)
+            scale = torch.full((len(self),), scale, device=self.device)
         new_points_list = []
         points_list = self.points_list()
         for i, old_points in enumerate(points_list):