extend sample_points_from_meshes with texture

Summary:
Enhanced `sample_points_from_meshes` with texture sampling

* This new feature is used to return textures corresponding to the sampled points in `sample_points_from_meshes`

Reviewed By: nikhilaravi

Differential Revision: D24031525

fbshipit-source-id: 8e5d8f784cc38aa391aa8e84e54423bd9fad7ad1

pytorch3d/ops/sample_points_from_meshes.py

@@ -11,11 +11,19 @@
 import torch
 from pytorch3d.ops.mesh_face_areas_normals import mesh_face_areas_normals
 from pytorch3d.ops.packed_to_padded import packed_to_padded
+from pytorch3d.renderer.mesh.rasterizer import Fragments as MeshFragments
 
 
 def sample_points_from_meshes(
-    meshes, num_samples: int = 10000, return_normals: bool = False
-) -> Union[torch.Tensor, Tuple[torch.Tensor, torch.Tensor]]:
+    meshes,
+    num_samples: int = 10000,
+    return_normals: bool = False,
+    return_textures: bool = False,
+) -> Union[
+    torch.Tensor,
+    Tuple[torch.Tensor, torch.Tensor],
+    Tuple[torch.Tensor, torch.Tensor, torch.Tensor],
+]:
     """
     Convert a batch of meshes to a pointcloud by uniformly sampling points on
     the surface of the mesh with probability proportional to the face area.
@@ -24,10 +32,10 @@ def sample_points_from_meshes(
         meshes: A Meshes object with a batch of N meshes.
         num_samples: Integer giving the number of point samples per mesh.
         return_normals: If True, return normals for the sampled points.
-        eps: (float) used to clamp the norm of the normals to avoid dividing by 0.
+        return_textures: If True, return textures for the sampled points.
 
     Returns:
-        2-element tuple containing
+        3-element tuple containing
 
         - **samples**: FloatTensor of shape (N, num_samples, 3) giving the
           coordinates of sampled points for each mesh in the batch. For empty
@@ -36,13 +44,28 @@ def sample_points_from_meshes(
           to each sampled point. Only returned if return_normals is True.
           For empty meshes the corresponding row in the normals array will
           be filled with 0.
+        - **textures**: FloatTensor of shape (N, num_samples, C) giving a C-dimensional
+          texture vector to each sampled point. Only returned if return_textures is True.
+          For empty meshes the corresponding row in the textures array will
+          be filled with 0.
+
+        Note that in a future releases, we will replace the 3-element tuple output
+        with a `Pointclouds` datastructure, as follows
+
+        .. code-block:: python
+
+            Poinclouds(samples, normals=normals, features=textures)
     """
     if meshes.isempty():
         raise ValueError("Meshes are empty.")
 
     verts = meshes.verts_packed()
     if not torch.isfinite(verts).all():
         raise ValueError("Meshes contain nan or inf.")
+
+    if return_textures and meshes.textures is None:
+        raise ValueError("Meshes do not contain textures.")
+
     faces = meshes.faces_packed()
     mesh_to_face = meshes.mesh_to_faces_packed_first_idx()
     num_meshes = len(meshes)
@@ -66,7 +89,7 @@ def sample_points_from_meshes(
         sample_face_idxs += mesh_to_face[meshes.valid].view(num_valid_meshes, 1)
 
     # Get the vertex coordinates of the sampled faces.
-    face_verts = verts[faces.long()]
+    face_verts = verts[faces]
     v0, v1, v2 = face_verts[:, 0], face_verts[:, 1], face_verts[:, 2]
 
     # Randomly generate barycentric coords.
@@ -92,9 +115,29 @@ def sample_points_from_meshes(
         vert_normals = vert_normals[sample_face_idxs]
         normals[meshes.valid] = vert_normals
 
+    if return_textures:
+        # fragment data are of shape NxHxWxK. Here H=S, W=1 & K=1.
+        pix_to_face = sample_face_idxs.view(len(meshes), num_samples, 1, 1)  # NxSx1x1
+        bary = torch.stack((w0, w1, w2), dim=2).unsqueeze(2).unsqueeze(2)  # NxSx1x1x3
+        # zbuf and dists are not used in `sample_textures` so we initialize them with dummy
+        dummy = torch.zeros(
+            (len(meshes), num_samples, 1, 1), device=meshes.device, dtype=torch.float32
+        )  # NxSx1x1
+        fragments = MeshFragments(
+            pix_to_face=pix_to_face, zbuf=dummy, bary_coords=bary, dists=dummy
+        )
+        textures = meshes.sample_textures(fragments)  # NxSx1x1xC
+        textures = textures[:, :, 0, 0, :]  # NxSxC
+
+    # return
+    # TODO(gkioxari) consider returning a Pointclouds instance [breaking]
+    if return_normals and return_textures:
+        return samples, normals, textures
+    if return_normals:  # return_textures is False
         return samples, normals
-    else:
-        return samples
+    if return_textures:  # return_normals is False
+        return samples, textures
+    return samples
 
 
 def _rand_barycentric_coords(

tests/test_sample_points_from_meshes.py

@@ -4,13 +4,31 @@
 import unittest
 from pathlib import Path
 
+import numpy as np
 import torch
 from common_testing import TestCaseMixin, get_random_cuda_device
+from PIL import Image
+from pytorch3d.io import load_objs_as_meshes
 from pytorch3d.ops import sample_points_from_meshes
-from pytorch3d.structures.meshes import Meshes
+from pytorch3d.renderer import TexturesVertex
+from pytorch3d.renderer.cameras import FoVPerspectiveCameras, look_at_view_transform
+from pytorch3d.renderer.mesh.rasterize_meshes import barycentric_coordinates
+from pytorch3d.renderer.points import (
+    NormWeightedCompositor,
+    PointsRasterizationSettings,
+    PointsRasterizer,
+    PointsRenderer,
+)
+from pytorch3d.structures import Meshes, Pointclouds
 from pytorch3d.utils.ico_sphere import ico_sphere
 
 
+# If DEBUG=True, save out images generated in the tests for debugging.
+# All saved images have prefix DEBUG_
+DEBUG = False
+DATA_DIR = Path(__file__).resolve().parent / "data"
+
+
 class TestSamplePoints(TestCaseMixin, unittest.TestCase):
     def setUp(self) -> None:
         super().setUp()
@@ -22,18 +40,27 @@ def init_meshes(
         num_verts: int = 1000,
         num_faces: int = 3000,
         device: str = "cpu",
+        add_texture: bool = False,
     ):
         device = torch.device(device)
         verts_list = []
         faces_list = []
+        texts_list = []
         for _ in range(num_meshes):
             verts = torch.rand((num_verts, 3), dtype=torch.float32, device=device)
             faces = torch.randint(
                 num_verts, size=(num_faces, 3), dtype=torch.int64, device=device
             )
+            texts = torch.rand((num_verts, 3), dtype=torch.float32, device=device)
             verts_list.append(verts)
             faces_list.append(faces)
-        meshes = Meshes(verts_list, faces_list)
+            texts_list.append(texts)
+
+        # create textures
+        textures = None
+        if add_texture:
+            textures = TexturesVertex(texts_list)
+        meshes = Meshes(verts=verts_list, faces=faces_list, textures=textures)
 
         return meshes
 
@@ -264,6 +291,147 @@ def test_verts_nan(self):
                         meshes, num_samples=100, return_normals=True
                     )
 
+    def test_outputs(self):
+
+        for add_texture in (True, False):
+            meshes = TestSamplePoints.init_meshes(
+                device=torch.device("cuda:0"), add_texture=add_texture
+            )
+            out1 = sample_points_from_meshes(meshes, num_samples=100)
+            self.assertTrue(torch.is_tensor(out1))
+
+            out2 = sample_points_from_meshes(
+                meshes, num_samples=100, return_normals=True
+            )
+            self.assertTrue(isinstance(out2, tuple) and len(out2) == 2)
+
+            if add_texture:
+                out3 = sample_points_from_meshes(
+                    meshes, num_samples=100, return_textures=True
+                )
+                self.assertTrue(isinstance(out3, tuple) and len(out3) == 2)
+
+                out4 = sample_points_from_meshes(
+                    meshes, num_samples=100, return_normals=True, return_textures=True
+                )
+                self.assertTrue(isinstance(out4, tuple) and len(out4) == 3)
+            else:
+                with self.assertRaisesRegex(
+                    ValueError, "Meshes do not contain textures."
+                ):
+                    sample_points_from_meshes(
+                        meshes, num_samples=100, return_textures=True
+                    )
+
+                with self.assertRaisesRegex(
+                    ValueError, "Meshes do not contain textures."
+                ):
+                    sample_points_from_meshes(
+                        meshes,
+                        num_samples=100,
+                        return_normals=True,
+                        return_textures=True,
+                    )
+
+    def test_texture_sampling(self):
+        device = torch.device("cuda:0")
+        batch_size = 6
+        # verts
+        verts = torch.rand((batch_size, 6, 3), device=device, dtype=torch.float32)
+        verts[:, :3, 2] = 1.0
+        verts[:, 3:, 2] = -1.0
+        # textures
+        texts = torch.rand((batch_size, 6, 3), device=device, dtype=torch.float32)
+        # faces
+        faces = torch.tensor([[0, 1, 2], [3, 4, 5]], device=device, dtype=torch.int64)
+        faces = faces.view(1, 2, 3).expand(batch_size, -1, -1)
+
+        meshes = Meshes(verts=verts, faces=faces, textures=TexturesVertex(texts))
+
+        num_samples = 24
+        samples, normals, textures = sample_points_from_meshes(
+            meshes, num_samples=num_samples, return_normals=True, return_textures=True
+        )
+
+        textures_naive = torch.zeros(
+            (batch_size, num_samples, 3), dtype=torch.float32, device=device
+        )
+        for n in range(batch_size):
+            for i in range(num_samples):
+                p = samples[n, i]
+                if p[2] > 0.0:  # sampled from 1st face
+                    v0, v1, v2 = verts[n, 0, :2], verts[n, 1, :2], verts[n, 2, :2]
+                    w0, w1, w2 = barycentric_coordinates(p[:2], v0, v1, v2)
+                    t0, t1, t2 = texts[n, 0], texts[n, 1], texts[n, 2]
+                else:  # sampled from 2nd face
+                    v0, v1, v2 = verts[n, 3, :2], verts[n, 4, :2], verts[n, 5, :2]
+                    w0, w1, w2 = barycentric_coordinates(p[:2], v0, v1, v2)
+                    t0, t1, t2 = texts[n, 3], texts[n, 4], texts[n, 5]
+
+                tt = w0 * t0 + w1 * t1 + w2 * t2
+                textures_naive[n, i] = tt
+
+        self.assertClose(textures, textures_naive)
+
+    def test_texture_sampling_cow(self):
+        # test texture sampling for the cow example by converting
+        # the cow mesh and its texture uv to a pointcloud with texture
+
+        device = torch.device("cuda:0")
+        obj_dir = Path(__file__).resolve().parent.parent / "docs/tutorials/data"
+        obj_filename = obj_dir / "cow_mesh/cow.obj"
+
+        for text_type in ("uv", "atlas"):
+            # Load mesh + texture
+            if text_type == "uv":
+                mesh = load_objs_as_meshes(
+                    [obj_filename], device=device, load_textures=True, texture_wrap=None
+                )
+            elif text_type == "atlas":
+                mesh = load_objs_as_meshes(
+                    [obj_filename],
+                    device=device,
+                    load_textures=True,
+                    create_texture_atlas=True,
+                    texture_atlas_size=8,
+                    texture_wrap=None,
+                )
+
+            points, normals, textures = sample_points_from_meshes(
+                mesh, num_samples=50000, return_normals=True, return_textures=True
+            )
+            pointclouds = Pointclouds(points, normals=normals, features=textures)
+
+            for pos in ("front", "back"):
+                # Init rasterizer settings
+                if pos == "back":
+                    azim = 0.0
+                elif pos == "front":
+                    azim = 180
+                R, T = look_at_view_transform(2.7, 0, azim)
+                cameras = FoVPerspectiveCameras(device=device, R=R, T=T)
+
+                raster_settings = PointsRasterizationSettings(
+                    image_size=512, radius=1e-2, points_per_pixel=1
+                )
+
+                rasterizer = PointsRasterizer(
+                    cameras=cameras, raster_settings=raster_settings
+                )
+                compositor = NormWeightedCompositor()
+                renderer = PointsRenderer(rasterizer=rasterizer, compositor=compositor)
+                images = renderer(pointclouds)
+
+                rgb = images[0, ..., :3].squeeze().cpu()
+                if DEBUG:
+                    filename = "DEBUG_cow_mesh_to_pointcloud_%s_%s.png" % (
+                        text_type,
+                        pos,
+                    )
+                    Image.fromarray((rgb.numpy() * 255).astype(np.uint8)).save(
+                        DATA_DIR / filename
+                    )
+
     @staticmethod
     def sample_points_with_init(
         num_meshes: int,