Geometry Nodes: fix attribute propagation in Delete Geometry node

Previously, attribute propagation did not work correctly in when only
deleting edges and faces (but not points). Face and face corner attributes
were propagated wrongly or not at all respectively.

In order to keep the patch relatively small for the release branch,
it does not include some small optimizations. These can be done in 3.1:
* Use a `Span<int>` instead of `IndexMask` to avoid creating an
  unnecessary `Vector<int64_t>`.
* Only prepare index mappings when there are actually attributes to
  propagate.

Differential Revision: https://developer.blender.org/D13338

1 files changed, 43 insertions, 11 deletions

diff --git a/source/blender/nodes/geometry/nodes/node_geo_delete_geometry.cc b/source/blender/nodes/geometry/nodes/node_geo_delete_geometry.cc
index e0a3faaefb0..b0df6428a06 100644
--- a/source/blender/nodes/geometry/nodes/node_geo_delete_geometry.cc
+++ b/source/blender/nodes/geometry/nodes/node_geo_delete_geometry.cc
@@ -197,6 +197,27 @@ static void copy_attributes_based_on_mask(const Map<AttributeIDRef, AttributeKin
   }
 }
 
+static void copy_face_corner_attributes(const Map<AttributeIDRef, AttributeKind> &attributes,
+                                        const GeometryComponent &in_component,
+                                        GeometryComponent &out_component,
+                                        const int num_selected_loops,
+                                        const Span<int> selected_poly_indices,
+                                        const Mesh &mesh_in)
+{
+  Vector<int64_t> indices;
+  indices.reserve(num_selected_loops);
+  for (const int src_poly_index : selected_poly_indices) {
+    const MPoly &src_poly = mesh_in.mpoly[src_poly_index];
+    const int src_loop_start = src_poly.loopstart;
+    const int tot_loop = src_poly.totloop;
+    for (const int i : IndexRange(tot_loop)) {
+      indices.append_unchecked(src_loop_start + i);
+    }
+  }
+  copy_attributes_based_on_mask(
+      attributes, in_component, out_component, ATTR_DOMAIN_CORNER, IndexMask(indices));
+}
+
 static void copy_masked_edges_to_new_mesh(const Mesh &src_mesh, Mesh &dst_mesh, Span<int> edge_map)
 {
   BLI_assert(src_mesh.totedge == edge_map.size());
@@ -1051,12 +1072,17 @@ static void do_mesh_separation(GeometrySet &geometry_set,
                                     out_component,
                                     ATTR_DOMAIN_EDGE,
                                     index_mask_indices(edge_map, num_selected_edges, indices));
-      copy_attributes_based_on_mask(
-          attributes,
-          in_component,
-          out_component,
-          ATTR_DOMAIN_FACE,
-          index_mask_indices(selected_poly_indices, num_selected_polys, indices));
+      copy_attributes_based_on_mask(attributes,
+                                    in_component,
+                                    out_component,
+                                    ATTR_DOMAIN_FACE,
+                                    IndexMask(Vector<int64_t>(selected_poly_indices.as_span())));
+      copy_face_corner_attributes(attributes,
+                                  in_component,
+                                  out_component,
+                                  num_selected_loops,
+                                  selected_poly_indices,
+                                  mesh_in);
       break;
     }
     case GEO_NODE_DELETE_GEOMETRY_MODE_ONLY_FACE: {
@@ -1103,11 +1129,17 @@ static void do_mesh_separation(GeometrySet &geometry_set,
       copy_attributes(
           attributes, in_component, out_component, {ATTR_DOMAIN_POINT, ATTR_DOMAIN_EDGE});
       copy_masked_polys_to_new_mesh(mesh_in, *mesh_out, selected_poly_indices, new_loop_starts);
-      Vector<int64_t> indices;
-      const IndexMask mask = index_mask_indices(
-          selected_poly_indices, num_selected_polys, indices);
-      copy_attributes_based_on_mask(
-          attributes, in_component, out_component, ATTR_DOMAIN_FACE, mask);
+      copy_attributes_based_on_mask(attributes,
+                                    in_component,
+                                    out_component,
+                                    ATTR_DOMAIN_FACE,
+                                    IndexMask(Vector<int64_t>(selected_poly_indices.as_span())));
+      copy_face_corner_attributes(attributes,
+                                  in_component,
+                                  out_component,
+                                  num_selected_loops,
+                                  selected_poly_indices,
+                                  mesh_in);
       break;
     }
   }