Merge branch 'fix/explicit_quadrature_indexing_regression' into 'main'

Fix quadrature point indexing in `wp.fem.ExplicitQuadrature`

See merge request omniverse/warp!707

CHANGELOG.md

@@ -19,6 +19,7 @@
 - Fix handling of integer indices in the `input_output_mask` argument to `autograd.jacobian` and `autograd.jacobian_fd` ([GH-289](https://github.com/NVIDIA/warp/issues/289)).
 - Fix `ModelBuilder.collapse_fixed_joints()` to correctly update the body centers of mass and the `ModelBuilder.articulation_start` array.
 - Fix precedence of closure constants over global constants
+- Fix quadrature point indexing in `wp.fem.ExplicitQuadrature` (regression from 1.3.0)
 
 ## [1.3.1] - 2024-07-27
 

warp/fem/quadrature/quadrature.py

@@ -336,6 +336,7 @@ def max_points_per_element(self):
     @cache.cached_arg_value
     def arg_value(self, device):
         arg = self.Arg()
+        arg.points_per_cell = self._points_per_cell
         arg.points = self._points.to(device)
         arg.weights = self._weights.to(device)
 

warp/tests/test_fem.py

@@ -1315,6 +1315,8 @@ def test_particle_quadratures(test, device):
     geo = fem.Grid2D(res=wp.vec2i(2))
 
     domain = fem.Cells(geo)
+
+    # Explicit quadrature
     points, weights = domain.reference_element().instantiate_quadrature(order=4, family=fem.Polynomial.GAUSS_LEGENDRE)
     points_per_cell = len(points)
 
@@ -1329,9 +1331,16 @@ def test_particle_quadratures(test, device):
     test.assertEqual(explicit_quadrature.max_points_per_element(), points_per_cell)
     test.assertEqual(explicit_quadrature.total_point_count(), points_per_cell * geo.cell_count())
 
+    # test integration accuracy
     val = fem.integrate(_bicubic, quadrature=explicit_quadrature)
     test.assertAlmostEqual(val, 1.0 / 16, places=5)
 
+    # test indexing validity
+    arr = wp.empty(explicit_quadrature.total_point_count(), dtype=float)
+    fem.interpolate(_piecewise_constant, dest=arr, quadrature=explicit_quadrature)
+    assert_np_equal(arr.numpy(), np.arange(geo.cell_count()).repeat(points_per_cell))
+
+    # PIC quadrature
     element_indices = wp.array([3, 3, 2], dtype=int, device=device)
     element_coords = wp.array(
         [
@@ -1349,6 +1358,7 @@ def test_particle_quadratures(test, device):
     test.assertEqual(pic_quadrature.total_point_count(), 3)
     test.assertEqual(pic_quadrature.active_cell_count(), 2)
 
+    # Test integration accuracy
     val = fem.integrate(_piecewise_constant, quadrature=pic_quadrature)
     test.assertAlmostEqual(val, 1.25, places=5)