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Submesh 3/n: Add submeshing functionality

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Summary:
Copypasting the docstring:
```
        Split a mesh into submeshes, defined by face indices of the original Meshes object.

        Args:
          face_indices:
            Let the original mesh have verts_list() of length N.
            Can be either
              - List of length N. The n-th element is a list of length num_submeshes_n
                (empty lists are allowed). Each element of the n-th sublist is a LongTensor
                of length num_faces.
              - List of length N. The n-th element is a possibly empty padded LongTensor of
                shape (num_submeshes_n, max_num_faces).

        Returns:
          Meshes object with selected submeshes. The submesh tensors are cloned.

        Currently submeshing only works with no textures or with the TexturesVertex texture.

        Example:

        Take a Meshes object `cubes` with 4 meshes, each a translated cube. Then:
            * len(cubes) is 4, len(cubes.verts_list()) is 4, len(cubes.faces_list()) is 4,
            * [cube_verts.size for cube_verts in cubes.verts_list()] is [8, 8, 8, 8],
            * [cube_faces.size for cube_faces in cubes.faces_list()] if [6, 6, 6, 6],

        Now let front_facet, top_and_bottom, all_facets be LongTensors of
        sizes (2), (4), and (12), each picking up a number of facets of a cube by specifying
        the appropriate triangular faces.

        Then let `subcubes = cubes.submeshes([[front_facet, top_and_bottom], [], [all_facets], []])`.
            * len(subcubes) is 3.
            * subcubes[0] is the front facet of the cube contained in cubes[0].
            * subcubes[1] is a mesh containing the (disconnected) top and bottom facets of cubes[0].
            * subcubes[2] is a clone of cubes[2].
            * There are no submeshes of cubes[1] and cubes[3] in subcubes.
            * subcubes[0] and subcubes[1] are not watertight. subcubes[2] is.
```

Reviewed By: bottler

Differential Revision: D35440657

fbshipit-source-id: 8a6d2d300ce226b5b9eb440688528b5e795195a1
This commit is contained in:
Krzysztof Chalupka 2022-04-11 16:27:53 -07:00 committed by Facebook GitHub Bot
parent 8596fcacd2
commit 050f650ae8
2 changed files with 249 additions and 0 deletions
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109
pytorch3d/structures/meshes.py
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@ -1556,6 +1556,115 @@ class Meshes:
else:
raise ValueError("Meshes does not have textures")
def submeshes(
self,
face_indices: Union[
List[List[torch.LongTensor]], List[torch.LongTensor], torch.LongTensor
],
) -> "Meshes":
"""
Split a batch of meshes into a batch of submeshes.
The return value is a Meshes object representing
[mesh restricted to only faces indexed by selected_faces
for mesh, selected_faces_list in zip(self, face_indices)
for faces in selected_faces_list]
Args:
face_indices:
Let the original mesh have verts_list() of length N.
Can be either
- List of lists of LongTensors. The n-th element is a list of length
num_submeshes_n (empty lists are allowed). The k-th element of the n-th
sublist is a LongTensor of length num_faces_submesh_n_k.
- List of LongTensors. The n-th element is a (possibly empty) LongTensor
of shape (num_submeshes_n, num_faces_n).
- A LongTensor of shape (N, num_submeshes_per_mesh, num_faces_per_submesh)
where all meshes in the batch will have the same number of submeshes.
This will result in an output Meshes object with batch size equal to
N * num_submeshes_per_mesh.
Returns:
Meshes object of length `sum(len(ids) for ids in face_indices)`.
Submeshing only works with no textures or with the TexturesVertex texture.
Example 1:
If `meshes` has batch size 1, and `face_indices` is a 1D LongTensor,
then `meshes.submeshes([[face_indices]]) and
`meshes.submeshes(face_indices[None, None])` both produce a Meshes of length 1,
containing a single submesh with a subset of `meshes`' faces, whose indices are
specified by `face_indices`.
Example 2:
Take a Meshes object `cubes` with 4 meshes, each a translated cube. Then:
* len(cubes) is 4, len(cubes.verts_list()) is 4, len(cubes.faces_list()) 4,
* [cube_verts.size for cube_verts in cubes.verts_list()] is [8, 8, 8, 8],
* [cube_faces.size for cube_faces in cubes.faces_list()] if [6, 6, 6, 6],
Now let front_facet, top_and_bottom, all_facets be LongTensors of
sizes (2), (4), and (12), each picking up a number of facets of a cube by
specifying the appropriate triangular faces.
Then let `subcubes = cubes.submeshes([[front_facet, top_and_bottom], [],
[all_facets], []])`.
* len(subcubes) is 3.
* subcubes[0] is the front facet of the cube contained in cubes[0].
* subcubes[1] is a mesh containing the (disconnected) top and bottom facets
of cubes[0].
* subcubes[2] is cubes[2].
* There are no submeshes of cubes[1] and cubes[3] in subcubes.
* subcubes[0] and subcubes[1] are not watertight. subcubes[2] is.
"""
if not (
self.textures is None or type(self.textures).__name__ == "TexturesVertex"
):
raise ValueError(
"Submesh extraction only works with no textures or TexturesVertex."
)
if len(face_indices) != len(self):
raise ValueError(
"You must specify exactly one set of submeshes"
" for each mesh in this Meshes object."
)
sub_verts = []
sub_faces = []
for face_ids_per_mesh, faces, verts in zip(
face_indices, self.faces_list(), self.verts_list()
):
for submesh_face_ids in face_ids_per_mesh:
faces_to_keep = faces[submesh_face_ids]
# Say we are keeping two faces from a mesh with six vertices:
# faces_to_keep = [[0, 6, 4],
# [0, 2, 6]]
# Then we want verts_to_keep to contain only vertices [0, 2, 4, 6]:
vertex_ids_to_keep = torch.unique(faces_to_keep, sorted=True)
sub_verts.append(verts[vertex_ids_to_keep])
# Now, convert faces_to_keep to use the new vertex ids.
# In our example, instead of
# [[0, 6, 4],
# [0, 2, 6]]
# we want faces_to_keep to be
# [[0, 3, 2],
# [0, 1, 3]],
# as each point id got reduced to its sort rank.
_, ids_of_unique_ids_in_sorted = torch.unique(
faces_to_keep, return_inverse=True
)
sub_faces.append(ids_of_unique_ids_in_sorted)
return self.__class__(
verts=sub_verts,
faces=sub_faces,
)
def join_meshes_as_batch(meshes: List[Meshes], include_textures: bool = True) -> Meshes:
"""

140
tests/test_meshes.py
View File

@ -233,6 +233,46 @@ def to_sorted(mesh: Meshes) -> "Meshes":
return other
def init_cube_meshes(device: str = "cpu"):
# Make Meshes with four cubes translated from the origin by varying amounts.
verts = torch.FloatTensor(
[
[0, 0, 0],
[1, 0, 0], # 1->0
[1, 1, 0], # 2->1
[0, 1, 0], # 3->2
[0, 1, 1], # 3
[1, 1, 1], # 4
[1, 0, 1], # 5
[0, 0, 1],
],
device=device,
)
faces = torch.FloatTensor(
[
[0, 2, 1],
[0, 3, 2],
[2, 3, 4], # 1,2, 3
[2, 4, 5], #
[1, 2, 5], #
[1, 5, 6], #
[0, 7, 4],
[0, 4, 3],
[5, 4, 7],
[5, 7, 6],
[0, 6, 7],
[0, 1, 6],
],
device=device,
)
return Meshes(
verts=[verts, verts + 1, verts + 2, verts + 3],
faces=[faces, faces, faces, faces],
)
class TestMeshes(TestCaseMixin, unittest.TestCase):
def setUp(self) -> None:
np.random.seed(42)
@ -1257,6 +1297,106 @@ class TestMeshes(TestCaseMixin, unittest.TestCase):
yes_normals.offset_verts_(torch.FloatTensor([1, 2, 3]).expand(12, 3))
self.assertFalse(torch.allclose(yes_normals.verts_normals_padded(), verts))
def test_submeshes(self):
empty_mesh = Meshes([], [])
# Four cubes with offsets [0, 1, 2, 3].
cubes = init_cube_meshes()
# Extracting an empty submesh from an empty mesh is allowed, but extracting
# a nonempty submesh from an empty mesh should result in a value error.
self.assertTrue(mesh_structures_equal(empty_mesh.submeshes([]), empty_mesh))
self.assertTrue(
mesh_structures_equal(cubes.submeshes([[], [], [], []]), empty_mesh)
)
with self.assertRaisesRegex(
ValueError, "You must specify exactly one set of submeshes"
):
empty_mesh.submeshes([torch.LongTensor([0])])
# Check that we can chop the cube up into its facets.
subcubes = to_sorted(
cubes.submeshes(
[ # Do not submesh cube#1.
[],
# Submesh the front face and the top-and-bottom of cube#2.
[
torch.LongTensor([0, 1]),
torch.LongTensor([2, 3, 4, 5]),
],
# Do not submesh cube#3.
[],
# Submesh the whole cube#4 (clone it).
[torch.LongTensor(list(range(12)))],
]
)
)
# The cube should've been chopped into three submeshes.
self.assertEquals(len(subcubes), 3)
# The first submesh should be a single facet of cube#2.
front_facet = to_sorted(
Meshes(
verts=torch.FloatTensor([[[0, 0, 0], [1, 0, 0], [1, 1, 0], [0, 1, 0]]])
+ 1,
faces=torch.LongTensor([[[0, 2, 1], [0, 3, 2]]]),
)
)
self.assertTrue(mesh_structures_equal(front_facet, subcubes[0]))
# The second submesh should be the top and bottom facets of cube#2.
top_and_bottom = Meshes(
verts=torch.FloatTensor(
[[[1, 0, 0], [1, 1, 0], [0, 1, 0], [0, 1, 1], [1, 1, 1], [1, 0, 1]]]
)
+ 1,
faces=torch.LongTensor([[[1, 2, 3], [1, 3, 4], [0, 1, 4], [0, 4, 5]]]),
)
self.assertTrue(mesh_structures_equal(to_sorted(top_and_bottom), subcubes[1]))
# The last submesh should be all of cube#3.
self.assertTrue(mesh_structures_equal(to_sorted(cubes[3]), subcubes[2]))
# Test alternative input parameterization: list of LongTensors.
two_facets = torch.LongTensor([[0, 1], [4, 5]])
subcubes = to_sorted(cubes.submeshes([two_facets, [], two_facets, []]))
expected_verts = torch.FloatTensor(
[
[[0, 0, 0], [0, 1, 0], [1, 0, 0], [1, 1, 0]],
[[1, 0, 0], [1, 0, 1], [1, 1, 0], [1, 1, 1]],
[[2, 2, 2], [2, 3, 2], [3, 2, 2], [3, 3, 2]],
[[3, 2, 2], [3, 2, 3], [3, 3, 2], [3, 3, 3]],
]
)
expected_faces = torch.LongTensor(
[
[[0, 3, 2], [0, 1, 3]],
[[0, 2, 3], [0, 3, 1]],
[[0, 3, 2], [0, 1, 3]],
[[0, 2, 3], [0, 3, 1]],
]
)
expected_meshes = Meshes(verts=expected_verts, faces=expected_faces)
self.assertTrue(mesh_structures_equal(subcubes, expected_meshes))
# Test alternative input parameterization: a single LongTensor.
triangle_per_mesh = torch.LongTensor([[[0]], [[1]], [[4]], [[5]]])
subcubes = to_sorted(cubes.submeshes(triangle_per_mesh))
expected_verts = torch.FloatTensor(
[
[[0, 0, 0], [1, 0, 0], [1, 1, 0]],
[[1, 1, 1], [1, 2, 1], [2, 2, 1]],
[[3, 2, 2], [3, 3, 2], [3, 3, 3]],
[[4, 3, 3], [4, 3, 4], [4, 4, 4]],
]
)
expected_faces = torch.LongTensor(
[[[0, 2, 1]], [[0, 1, 2]], [[0, 1, 2]], [[0, 2, 1]]]
)
expected_meshes = Meshes(verts=expected_verts, faces=expected_faces)
self.assertTrue(mesh_structures_equal(subcubes, expected_meshes))
def test_compute_faces_areas_cpu_cuda(self):
num_meshes = 10
max_v = 100