Rebuild Mesh's PMF on vertex position changes

src/render/mesh.cpp

@@ -138,8 +138,8 @@ MI_VARIANT void Mesh<Float, Spectrum>::parameters_changed(const std::vector<std:
         if (has_vertex_normals())
             recompute_vertex_normals();
 
-        if (!m_area_pmf.empty() && (m_emitter || m_sensor))
-            ensure_pmf_built();
+        if (!m_area_pmf.empty() || m_emitter || m_sensor)
+            build_pmf();
 
         if (m_parameterization)
             m_parameterization = nullptr;

src/render/tests/test_mesh.py

@@ -1198,3 +1198,26 @@ def test32_shape_type(variant_scalar_rgb):
         "filename" : "resources/data/tests/ply/rectangle_uv.ply",
     })
     assert mesh.shape_type() == mi.ShapeType.Mesh.value;
+
+
+@fresolver_append_path
+def test33_rebuild_area_pmf(variants_vec_rgb):
+    mesh = mi.load_dict({
+        "type" : "ply",
+        "filename" : "resources/data/tests/ply/triangle.ply",
+        "face_normals" : True
+    })
+
+    surface_area_before = mesh.surface_area()
+
+    params = mi.traverse(mesh)
+    key = 'vertex_positions'
+
+    vertices = dr.unravel(mi.Point3f, params[key])
+    new_vertices = mi.Transform4f().scale(2) @ vertices
+    params[key] = dr.ravel(new_vertices)
+    params.update()
+
+    surface_area_after = mesh.surface_area()
+
+    assert surface_area_after == 4 * surface_area_before