Adding join_mesh in pytorch3d.structures.meshes

Summary: Adding a function in pytorch3d.structures.meshes to join multiple meshes into a Meshes object representing a single mesh. The function currently ignores all textures.

Reviewed By: nikhilaravi

Differential Revision: D21876908

fbshipit-source-id: 448602857e9d3d3f774d18bb4e93076f78329823

pytorch3d/structures/meshes.py

 # Copyright (c) Facebook, Inc. and its affiliates. All rights reserved.
 
-from typing import List
+from typing import List, Union
 
 import torch
 
@@ -1539,3 +1539,28 @@ def join_meshes_as_batch(meshes: List[Meshes], include_textures: bool = True):
 
     tex = Textures(**kwargs)
     return Meshes(verts=verts, faces=faces, textures=tex)
+
+
+def join_mesh(meshes: Union[Meshes, List[Meshes]]) -> Meshes:
+    """
+    Joins a batch of meshes in the form of a Meshes object or a list of Meshes
+    objects as a single mesh. If the input is a list, the Meshes objects in the list
+    must all be on the same device. This version ignores all textures in the input mehses.
+
+    Args:
+        meshes: Meshes object that contains a batch of meshes or a list of Meshes objects
+
+    Returns:
+        new Meshes object containing a single mesh
+    """
+    if isinstance(meshes, List):
+        meshes = join_meshes_as_batch(meshes, include_textures=False)
+
+    if len(meshes) == 1:
+        return meshes
+    verts = meshes.verts_packed()  # (sum(V_n), 3)
+    # Offset automatically done by faces_packed
+    faces = meshes.faces_packed()  # (sum(F_n), 3)
+
+    mesh = Meshes(verts=verts.unsqueeze(0), faces=faces.unsqueeze(0))
+    return mesh

tests/test_obj_io.py

@@ -14,6 +14,7 @@ from pytorch3d.io.mtl_io import (
     _bilinear_interpolation_vectorized,
 )
 from pytorch3d.structures import Meshes, Textures, join_meshes_as_batch
+from pytorch3d.structures.meshes import join_mesh
 from pytorch3d.utils import torus
 
 
@@ -648,6 +649,42 @@ class TestMeshObjIO(TestCaseMixin, unittest.TestCase):
         self.assertClose(cow3_tea.verts_list()[3], mesh_teapot.verts_list()[0])
         self.assertClose(cow3_tea.faces_list()[3], mesh_teapot.faces_list()[0])
 
+    def test_join_meshes(self):
+        """
+        Test that join_mesh joins single meshes and the corresponding values are
+        consistent with the single meshes.
+        """
+
+        # Load cow mesh.
+        DATA_DIR = Path(__file__).resolve().parent.parent / "docs/tutorials/data"
+        cow_obj = DATA_DIR / "cow_mesh/cow.obj"
+
+        cow_mesh = load_objs_as_meshes([cow_obj])
+        cow_verts, cow_faces = cow_mesh.get_mesh_verts_faces(0)
+        # Join a batch of three single meshes and check that the values are consistent
+        # with the individual meshes.
+        cow_mesh3 = join_mesh([cow_mesh, cow_mesh, cow_mesh])
+
+        def check_item(x, y, offset):
+            self.assertClose(torch.cat([x, x + offset, x + 2 * offset], dim=1), y)
+
+        check_item(cow_mesh.verts_padded(), cow_mesh3.verts_padded(), 0)
+        check_item(cow_mesh.faces_padded(), cow_mesh3.faces_padded(), cow_mesh._V)
+
+        # Test the joining of meshes of different sizes.
+        teapot_obj = DATA_DIR / "teapot.obj"
+        teapot_mesh = load_objs_as_meshes([teapot_obj])
+        teapot_verts, teapot_faces = teapot_mesh.get_mesh_verts_faces(0)
+
+        mix_mesh = join_mesh([cow_mesh, teapot_mesh])
+        mix_verts, mix_faces = mix_mesh.get_mesh_verts_faces(0)
+        self.assertEqual(len(mix_mesh), 1)
+
+        self.assertClose(mix_verts[: cow_mesh._V], cow_verts)
+        self.assertClose(mix_faces[: cow_mesh._F], cow_faces)
+        self.assertClose(mix_verts[cow_mesh._V :], teapot_verts)
+        self.assertClose(mix_faces[cow_mesh._F :], teapot_faces + cow_mesh._V)
+
     @staticmethod
     def _bm_save_obj(verts: torch.Tensor, faces: torch.Tensor, decimal_places: int):
         return lambda: save_obj(StringIO(), verts, faces, decimal_places)

tests/test_render_meshes.py

@@ -26,7 +26,7 @@ from pytorch3d.renderer.mesh.shader import (
     TexturedSoftPhongShader,
 )
 from pytorch3d.renderer.mesh.texturing import Textures
-from pytorch3d.structures.meshes import Meshes
+from pytorch3d.structures.meshes import Meshes, join_mesh
 from pytorch3d.utils.ico_sphere import ico_sphere
 
 
@@ -176,7 +176,7 @@ class TestRenderMeshes(TestCaseMixin, unittest.TestCase):
         # Init renderer
         rasterizer = MeshRasterizer(cameras=cameras, raster_settings=raster_settings)
         shaders = {
-            "phong": HardGouraudShader,
+            "phong": HardPhongShader,
             "gouraud": HardGouraudShader,
             "flat": HardFlatShader,
         }
@@ -369,3 +369,70 @@ class TestRenderMeshes(TestCaseMixin, unittest.TestCase):
                 )
 
             self.assertClose(rgb, image_ref, atol=0.05)
+
+    def test_joined_spheres(self):
+        """
+        Test a list of Meshes can be joined as a single mesh and
+        the single mesh is rendered correctly with Phong, Gouraud
+        and Flat Shaders.
+        """
+        device = torch.device("cuda:0")
+
+        # Init mesh with vertex textures.
+        # Initialize a list containing two ico spheres of different sizes.
+        sphere_list = [ico_sphere(3, device), ico_sphere(4, device)]
+        # [(42 verts, 80 faces), (162 verts, 320 faces)]
+        # The scale the vertices need to be set at to resize the spheres
+        scales = [0.25, 1]
+        # The distance the spheres ought to be offset horizontally to prevent overlap.
+        offsets = [1.2, -0.3]
+        # Initialize a list containing the adjusted sphere meshes.
+        sphere_mesh_list = []
+        for i in range(len(sphere_list)):
+            verts = sphere_list[i].verts_padded() * scales[i]
+            verts[0, :, 0] += offsets[i]
+            sphere_mesh_list.append(
+                Meshes(verts=verts, faces=sphere_list[i].faces_padded())
+            )
+        joined_sphere_mesh = join_mesh(sphere_mesh_list)
+        joined_sphere_mesh.textures = Textures(
+            verts_rgb=torch.ones_like(joined_sphere_mesh.verts_padded())
+        )
+
+        # Init rasterizer settings
+        R, T = look_at_view_transform(2.7, 0.0, 0.0)
+        cameras = OpenGLPerspectiveCameras(device=device, R=R, T=T)
+        raster_settings = RasterizationSettings(
+            image_size=512, blur_radius=0.0, faces_per_pixel=1
+        )
+
+        # Init shader settings
+        materials = Materials(device=device)
+        lights = PointLights(device=device)
+        lights.location = torch.tensor([0.0, 0.0, +2.0], device=device)[None]
+        blend_params = BlendParams(1e-4, 1e-4, (0, 0, 0))
+
+        # Init renderer
+        rasterizer = MeshRasterizer(cameras=cameras, raster_settings=raster_settings)
+        shaders = {
+            "phong": HardPhongShader,
+            "gouraud": HardGouraudShader,
+            "flat": HardFlatShader,
+        }
+        for (name, shader_init) in shaders.items():
+            shader = shader_init(
+                lights=lights,
+                cameras=cameras,
+                materials=materials,
+                blend_params=blend_params,
+            )
+            renderer = MeshRenderer(rasterizer=rasterizer, shader=shader)
+            image = renderer(joined_sphere_mesh)
+            rgb = image[..., :3].squeeze().cpu()
+            if DEBUG:
+                file_name = "DEBUG_joined_spheres_%s.png" % name
+                Image.fromarray((rgb.numpy() * 255).astype(np.uint8)).save(
+                    DATA_DIR / file_name
+                )
+            image_ref = load_rgb_image("test_joined_spheres_%s.png" % name, DATA_DIR)
+            self.assertClose(rgb, image_ref, atol=0.05)