1 files changed, 89 insertions, 0 deletions
diff --git a/source/blender/nodes/geometry/nodes/node_geo_mesh_face_set_boundaries.cc b/source/blender/nodes/geometry/nodes/node_geo_mesh_face_set_boundaries.cc
new file mode 100644
index 00000000000..88cccfb2f94
--- /dev/null
+++ b/source/blender/nodes/geometry/nodes/node_geo_mesh_face_set_boundaries.cc
@@ -0,0 +1,89 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+
+#include "DNA_mesh_types.h"
+#include "DNA_meshdata_types.h"
+
+#include "BKE_mesh.h"
+
+#include "node_geometry_util.hh"
+
+namespace blender::nodes::node_geo_mesh_face_set_boundaries_cc {
+
+static void node_declare(NodeDeclarationBuilder &b)
+{
+  b.add_input<decl::Int>(N_("Face Set"))
+      .default_value(0)
+      .hide_value()
+      .supports_field()
+      .description(N_("An identifier for the group of each face. All contiguous faces with the "
+                      "same value are in the same region"));
+  b.add_output<decl::Bool>(N_("Boundary Edges"))
+      .field_source()
+      .description(N_("The edges that lie on the boundaries between the different face sets"));
+}
+
+class BoundaryFieldInput final : public bke::MeshFieldInput {
+ private:
+  const Field<int> face_set;
+
+ public:
+  BoundaryFieldInput(const Field<int> face_set)
+      : bke::MeshFieldInput(CPPType::get<bool>(), "Boundary Field"), face_set(face_set)
+  {
+    category_ = Category::Generated;
+  }
+
+  GVArray get_varray_for_context(const Mesh &mesh,
+                                 const eAttrDomain domain,
+                                 const IndexMask /*mask*/) const final
+  {
+    const bke::MeshFieldContext face_context{mesh, ATTR_DOMAIN_FACE};
+    FieldEvaluator face_evaluator{face_context, mesh.totpoly};
+    face_evaluator.add(face_set);
+    face_evaluator.evaluate();
+    const VArray<int> face_set = face_evaluator.get_evaluated<int>(0);
+
+    Array<bool> boundary(mesh.totedge, false);
+    Array<bool> edge_visited(mesh.totedge, false);
+    Array<int> edge_face_set(mesh.totedge, 0);
+    const Span<MPoly> polys = mesh.polys();
+    const Span<MLoop> loops = mesh.loops();
+    for (const int i : polys.index_range()) {
+      const MPoly &poly = polys[i];
+      for (const MLoop &loop : loops.slice(poly.loopstart, poly.totloop)) {
+        const int edge = loop.e;
+        if (edge_visited[edge]) {
+          if (edge_face_set[edge] != face_set[i]) {
+            /* This edge is connected to two faces on different face sets. */
+            boundary[edge] = true;
+          }
+        }
+        edge_visited[edge] = true;
+        edge_face_set[edge] = face_set[i];
+      }
+    }
+    return mesh.attributes().adapt_domain<bool>(
+        VArray<bool>::ForContainer(std::move(boundary)), ATTR_DOMAIN_EDGE, domain);
+  }
+};
+
+static void node_geo_exec(GeoNodeExecParams params)
+{
+  const Field<int> face_set_field = params.extract_input<Field<int>>("Face Set");
+  Field<bool> face_set_boundaries{std::make_shared<BoundaryFieldInput>(face_set_field)};
+  params.set_output("Boundary Edges", std::move(face_set_boundaries));
+}
+
+}  // namespace blender::nodes::node_geo_mesh_face_set_boundaries_cc
+
+void register_node_type_geo_mesh_face_set_boundaries()
+{
+  namespace file_ns = blender::nodes::node_geo_mesh_face_set_boundaries_cc;
+
+  static bNodeType ntype;
+  geo_node_type_base(
+      &ntype, GEO_NODE_MESH_FACE_SET_BOUNDARIES, "Face Set Boundaries", NODE_CLASS_INPUT);
+  ntype.declare = file_ns::node_declare;
+  ntype.geometry_node_execute = file_ns::node_geo_exec;
+  nodeRegisterType(&ntype);
+}