1 files changed, 114 insertions, 0 deletions
diff --git a/source/blender/nodes/geometry/nodes/node_geo_flip_faces.cc b/source/blender/nodes/geometry/nodes/node_geo_flip_faces.cc
new file mode 100644
index 00000000000..41970d75dfe
--- /dev/null
+++ b/source/blender/nodes/geometry/nodes/node_geo_flip_faces.cc
@@ -0,0 +1,114 @@
+/*
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ */
+
+#include "BKE_mesh.h"
+#include "BKE_mesh_runtime.h"
+
+#include "DNA_mesh_types.h"
+#include "DNA_meshdata_types.h"
+
+#include "BKE_attribute_math.hh"
+
+#include "node_geometry_util.hh"
+
+namespace blender::nodes::node_geo_flip_faces_cc {
+
+static void node_declare(NodeDeclarationBuilder &b)
+{
+  b.add_input<decl::Geometry>(N_("Mesh")).supported_type(GEO_COMPONENT_TYPE_MESH);
+  b.add_input<decl::Bool>(N_("Selection")).default_value(true).hide_value().supports_field();
+  b.add_output<decl::Geometry>(N_("Mesh"));
+}
+
+static void mesh_flip_faces(MeshComponent &component, const Field<bool> &selection_field)
+{
+  GeometryComponentFieldContext field_context{component, ATTR_DOMAIN_FACE};
+  const int domain_size = component.attribute_domain_size(ATTR_DOMAIN_FACE);
+  if (domain_size == 0) {
+    return;
+  }
+  fn::FieldEvaluator evaluator{field_context, domain_size};
+  evaluator.add(selection_field);
+  evaluator.evaluate();
+  const IndexMask selection = evaluator.get_evaluated_as_mask(0);
+
+  Mesh *mesh = component.get_for_write();
+
+  mesh->mloop = (MLoop *)CustomData_duplicate_referenced_layer(
+      &mesh->ldata, CD_MLOOP, mesh->totloop);
+  Span<MPoly> polys{mesh->mpoly, mesh->totpoly};
+  MutableSpan<MLoop> loops{mesh->mloop, mesh->totloop};
+
+  for (const int i : selection.index_range()) {
+    const MPoly &poly = polys[selection[i]];
+    int start = poly.loopstart;
+    for (const int j : IndexRange(poly.totloop / 2)) {
+      const int index1 = start + j + 1;
+      const int index2 = start + poly.totloop - j - 1;
+      std::swap(loops[index1].v, loops[index2].v);
+      std::swap(loops[index1 - 1].e, loops[index2].e);
+    }
+  }
+
+  component.attribute_foreach(
+      [&](const bke::AttributeIDRef &attribute_id, const AttributeMetaData &meta_data) {
+        if (meta_data.domain == ATTR_DOMAIN_CORNER) {
+          OutputAttribute attribute = component.attribute_try_get_for_output(
+              attribute_id, ATTR_DOMAIN_CORNER, meta_data.data_type, nullptr);
+          attribute_math::convert_to_static_type(meta_data.data_type, [&](auto dummy) {
+            using T = decltype(dummy);
+            MutableSpan<T> dst_span = attribute.as_span<T>();
+            for (const int j : selection.index_range()) {
+              const MPoly &poly = polys[selection[j]];
+              dst_span.slice(poly.loopstart + 1, poly.totloop - 1).reverse();
+            }
+          });
+          attribute.save();
+        }
+        return true;
+      });
+}
+
+static void node_geo_exec(GeoNodeExecParams params)
+{
+  GeometrySet geometry_set = params.extract_input<GeometrySet>("Mesh");
+
+  const Field<bool> selection_field = params.extract_input<Field<bool>>("Selection");
+
+  geometry_set.modify_geometry_sets([&](GeometrySet &geometry_set) {
+    if (!geometry_set.has_mesh()) {
+      return;
+    }
+    MeshComponent &mesh_component = geometry_set.get_component_for_write<MeshComponent>();
+    mesh_flip_faces(mesh_component, selection_field);
+  });
+
+  params.set_output("Mesh", std::move(geometry_set));
+}
+
+}  // namespace blender::nodes::node_geo_flip_faces_cc
+
+void register_node_type_geo_flip_faces()
+{
+  namespace file_ns = blender::nodes::node_geo_flip_faces_cc;
+
+  static bNodeType ntype;
+
+  geo_node_type_base(&ntype, GEO_NODE_FLIP_FACES, "Flip Faces", NODE_CLASS_GEOMETRY);
+  ntype.geometry_node_execute = file_ns::node_geo_exec;
+  ntype.declare = file_ns::node_declare;
+  nodeRegisterType(&ntype);
+}