bugfix in cotcurv laplacian loss. closes #551 (#553)

Summary: Pull Request resolved: https://github.com/facebookresearch/pytorch3d/pull/553

Reviewed By: theschnitz

Differential Revision: D26257591

Pulled By: gkioxari

fbshipit-source-id: 899a3f733a77361e8572b0900a34b55764ff08f2

pytorch3d/loss/mesh_laplacian_smoothing.py

@@ -108,6 +108,7 @@ def mesh_laplacian_smoothing(meshes, method: str = "uniform"):
                 idx = norm_w > 0
                 norm_w[idx] = 1.0 / norm_w[idx]
             else:
+                L_sum = torch.sparse.sum(L, dim=1).to_dense().view(-1, 1)
                 norm_w = 0.25 * inv_areas
         else:
             raise ValueError("Method should be one of {uniform, cot, cotcurv}")
@@ -117,7 +118,7 @@ def mesh_laplacian_smoothing(meshes, method: str = "uniform"):
     elif method == "cot":
         loss = L.mm(verts_packed) * norm_w - verts_packed
     elif method == "cotcurv":
-        loss = (L.mm(verts_packed) - verts_packed) * norm_w
+        loss = (L.mm(verts_packed) - L_sum * verts_packed) * norm_w
     loss = loss.norm(dim=1)
 
     loss = loss * weights

tests/test_mesh_laplacian_smoothing.py

@@ -89,11 +89,12 @@ class TestLaplacianSmoothing(unittest.TestCase):
         inv_areas[idx] = 1.0 / inv_areas[idx]
 
         norm_w = L.sum(dim=1, keepdims=True)
+        L_sum = norm_w.clone()
         idx = norm_w > 0
         norm_w[idx] = 1.0 / norm_w[idx]
 
         if method == "cotcurv":
-            loss = (L.mm(verts_packed) - verts_packed) * inv_areas * 0.25
+            loss = (L.mm(verts_packed) - L_sum * verts_packed) * inv_areas * 0.25
             loss = loss.norm(dim=1)
         else:
             loss = L.mm(verts_packed) * norm_w - verts_packed
@@ -147,7 +148,7 @@ class TestLaplacianSmoothing(unittest.TestCase):
 
     def test_laplacian_smoothing_cot(self):
         """
-        Test Laplacian Smoothing with uniform weights.
+        Test Laplacian Smoothing with cot weights.
         """
         meshes = TestLaplacianSmoothing.init_meshes(10, 100, 300)
 
@@ -161,7 +162,7 @@ class TestLaplacianSmoothing(unittest.TestCase):
 
     def test_laplacian_smoothing_cotcurv(self):
         """
-        Test Laplacian Smoothing with uniform weights.
+        Test Laplacian Smoothing with cotcurv weights.
         """
         meshes = TestLaplacianSmoothing.init_meshes(10, 100, 300)