subsample pointclouds

Summary: New function to randomly subsample Pointclouds to a maximum size.

Reviewed By: nikhilaravi

Differential Revision: D30936533

fbshipit-source-id: 789eb5004b6a233034ec1c500f20f2d507a303ff

pytorch3d/structures/pointclouds.py

@@ -4,6 +4,10 @@
 # This source code is licensed under the BSD-style license found in the
 # LICENSE file in the root directory of this source tree.
 
+from itertools import zip_longest
+from typing import Sequence, Union
+
+import numpy as np
 import torch
 
 from ..common.types import Device, make_device
@@ -841,6 +845,54 @@ class Pointclouds:
         new_clouds = self.clone()
         return new_clouds.offset_(offsets_packed)
 
+    def subsample(self, max_points: Union[int, Sequence[int]]) -> "Pointclouds":
+        """
+        Subsample each cloud so that it has at most max_points points.
+
+        Args:
+            max_points: maximum number of points in each cloud.
+
+        Returns:
+            new Pointclouds object, or self if nothing to be done.
+        """
+        if isinstance(max_points, int):
+            max_points = [max_points] * len(self)
+        elif len(max_points) != len(self):
+            raise ValueError("wrong number of max_points supplied")
+        if all(
+            int(n_points) <= int(max_)
+            for n_points, max_ in zip(self.num_points_per_cloud(), max_points)
+        ):
+            return self
+
+        points_list = []
+        features_list = []
+        normals_list = []
+        for max_, n_points, points, features, normals in zip_longest(
+            map(int, max_points),
+            map(int, self.num_points_per_cloud()),
+            self.points_list(),
+            self.features_list() or (),
+            self.normals_list() or (),
+        ):
+            if n_points > max_:
+                keep_np = np.random.choice(n_points, max_, replace=False)
+                keep = torch.tensor(keep_np).to(points.device)
+                points = points[keep]
+                if features is not None:
+                    features = features[keep]
+                if normals is not None:
+                    normals = normals[keep]
+            points_list.append(points)
+            features_list.append(features)
+            normals_list.append(normals)
+
+        return Pointclouds(
+            points=points_list,
+            normals=self.normals_list() and normals_list,
+            features=self.features_list() and features_list,
+        )
+
     def scale_(self, scale):
         """
         Multiply the coordinates of this object by a scalar value.

pytorch3d/vis/plotly_vis.py

@@ -7,7 +7,6 @@
 import warnings
 from typing import Dict, List, NamedTuple, Optional, Tuple, Union
 
-import numpy as np
 import plotly.graph_objects as go
 import torch
 from plotly.subplots import make_subplots
@@ -644,31 +643,12 @@ def _add_pointcloud_trace(
         max_points_per_pointcloud: the number of points to render, which are randomly sampled.
         marker_size: the size of the rendered points
     """
-    pointclouds = pointclouds.detach().cpu()
+    pointclouds = pointclouds.detach().cpu().subsample(max_points_per_pointcloud)
     verts = pointclouds.points_packed()
     features = pointclouds.features_packed()
 
-    indices = None
-    if pointclouds.num_points_per_cloud().max() > max_points_per_pointcloud:
-        start_index = 0
-        index_list = []
-        for num_points in pointclouds.num_points_per_cloud():
-            if num_points > max_points_per_pointcloud:
-                indices_cloud = np.random.choice(
-                    num_points, max_points_per_pointcloud, replace=False
-                )
-                index_list.append(start_index + indices_cloud)
-            else:
-                index_list.append(start_index + np.arange(num_points))
-            start_index += num_points
-        indices = np.concatenate(index_list)
-        verts = verts[indices]
-
     color = None
     if features is not None:
-        if indices is not None:
-            # Only select features if we selected vertices above
-            features = features[indices]
         if features.shape[1] == 4:  # rgba
             template = "rgb(%d, %d, %d, %f)"
             rgb = (features[:, :3].clamp(0.0, 1.0) * 255).int()

tests/test_pointclouds.py

@@ -1057,6 +1057,45 @@ class TestPointclouds(TestCaseMixin, unittest.TestCase):
                         clouds.normals_packed(), torch.cat(normals_est_list, dim=0)
                     )
 
+    def test_subsample(self):
+        lengths = [4, 5, 13, 3]
+        points = [torch.rand(length, 3) for length in lengths]
+        features = [torch.rand(length, 5) for length in lengths]
+        normals = [torch.rand(length, 3) for length in lengths]
+
+        pcl1 = Pointclouds(points=points).cuda()
+        self.assertIs(pcl1, pcl1.subsample(13))
+        self.assertIs(pcl1, pcl1.subsample([6, 13, 13, 13]))
+
+        lengths_max_4 = torch.tensor([4, 4, 4, 3]).cuda()
+        for with_normals, with_features in itertools.product([True, False], repeat=2):
+            with self.subTest(f"{with_normals} {with_features}"):
+                pcl = Pointclouds(
+                    points=points,
+                    normals=normals if with_normals else None,
+                    features=features if with_features else None,
+                )
+                pcl_copy = pcl.subsample(max_points=4)
+                for length, points_ in zip(lengths_max_4, pcl_copy.points_list()):
+                    self.assertEqual(points_.shape, (length, 3))
+                if with_normals:
+                    for length, normals_ in zip(lengths_max_4, pcl_copy.normals_list()):
+                        self.assertEqual(normals_.shape, (length, 3))
+                else:
+                    self.assertIsNone(pcl_copy.normals_list())
+                if with_features:
+                    for length, features_ in zip(
+                        lengths_max_4, pcl_copy.features_list()
+                    ):
+                        self.assertEqual(features_.shape, (length, 5))
+                else:
+                    self.assertIsNone(pcl_copy.features_list())
+
+        pcl2 = Pointclouds(points=points)
+        pcl_copy2 = pcl2.subsample(lengths_max_4)
+        for length, points_ in zip(lengths_max_4, pcl_copy2.points_list()):
+            self.assertEqual(points_.shape, (length, 3))
+
     @staticmethod
     def compute_packed_with_init(
         num_clouds: int = 10, max_p: int = 100, features: int = 300