1 files changed, 96 insertions, 0 deletions
diff --git a/source/blender/nodes/geometry/nodes/node_geo_input_mesh_face_area.cc b/source/blender/nodes/geometry/nodes/node_geo_input_mesh_face_area.cc
new file mode 100644
index 00000000000..538b9e9682d
--- /dev/null
+++ b/source/blender/nodes/geometry/nodes/node_geo_input_mesh_face_area.cc
@@ -0,0 +1,96 @@
+/*
+ * 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 "DNA_mesh_types.h"
+#include "DNA_meshdata_types.h"
+
+#include "BKE_mesh.h"
+
+#include "node_geometry_util.hh"
+
+namespace blender::nodes::node_geo_input_mesh_face_area_cc {
+
+static void node_declare(NodeDeclarationBuilder &b)
+{
+  b.add_output<decl::Float>(N_("Area"))
+      .field_source()
+      .description(N_("The surface area of each of the mesh's faces"));
+}
+
+static VArray<float> construct_face_area_gvarray(const MeshComponent &component,
+                                                 const AttributeDomain domain)
+{
+  const Mesh *mesh = component.get_for_read();
+  if (mesh == nullptr) {
+    return {};
+  }
+
+  auto area_fn = [mesh](const int i) -> float {
+    const MPoly *mp = &mesh->mpoly[i];
+    return BKE_mesh_calc_poly_area(mp, &mesh->mloop[mp->loopstart], mesh->mvert);
+  };
+
+  return component.attribute_try_adapt_domain<float>(
+      VArray<float>::ForFunc(mesh->totpoly, area_fn), ATTR_DOMAIN_FACE, domain);
+}
+
+class FaceAreaFieldInput final : public GeometryFieldInput {
+ public:
+  FaceAreaFieldInput() : GeometryFieldInput(CPPType::get<float>(), "Face Area Field")
+  {
+    category_ = Category::Generated;
+  }
+
+  GVArray get_varray_for_context(const GeometryComponent &component,
+                                 const AttributeDomain domain,
+                                 IndexMask UNUSED(mask)) const final
+  {
+    if (component.type() == GEO_COMPONENT_TYPE_MESH) {
+      const MeshComponent &mesh_component = static_cast<const MeshComponent &>(component);
+      return construct_face_area_gvarray(mesh_component, domain);
+    }
+    return {};
+  }
+
+  uint64_t hash() const override
+  {
+    /* Some random constant hash. */
+    return 1346334523;
+  }
+
+  bool is_equal_to(const fn::FieldNode &other) const override
+  {
+    return dynamic_cast<const FaceAreaFieldInput *>(&other) != nullptr;
+  }
+};
+
+static void node_geo_exec(GeoNodeExecParams params)
+{
+  params.set_output("Area", Field<float>(std::make_shared<FaceAreaFieldInput>()));
+}
+
+}  // namespace blender::nodes::node_geo_input_mesh_face_area_cc
+
+void register_node_type_geo_input_mesh_face_area()
+{
+  namespace file_ns = blender::nodes::node_geo_input_mesh_face_area_cc;
+
+  static bNodeType ntype;
+  geo_node_type_base(&ntype, GEO_NODE_INPUT_MESH_FACE_AREA, "Face Area", NODE_CLASS_INPUT, 0);
+  ntype.declare = file_ns::node_declare;
+  ntype.geometry_node_execute = file_ns::node_geo_exec;
+  nodeRegisterType(&ntype);
+}