node_geo_input_mesh_face_area.cc

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/* SPDX-FileCopyrightText: 2023 Blender Authors
 *
 * SPDX-License-Identifier: GPL-2.0-or-later */
 
#include "BKE_mesh.hh"
 
#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>("Area")
      .translation_context(BLT_I18NCONTEXT_AMOUNT)
      .field_source()
      .description("The surface area of each of the mesh's faces");
}
 
static VArray<float> construct_face_area_varray(const Mesh &mesh, const AttrDomain domain)
{
  const Span<float3> positions = mesh.vert_positions();
  const OffsetIndices faces = mesh.faces();
  const Span<int> corner_verts = mesh.corner_verts();
 
  auto area_fn = [positions, faces, corner_verts](const int i) -> float {
    return bke::mesh::face_area_calc(positions, corner_verts.slice(faces[i]));
  };
 
  return mesh.attributes().adapt_domain<float>(
      VArray<float>::from_func(faces.size(), area_fn), AttrDomain::Face, domain);
}
 
class FaceAreaFieldInput final : public bke::MeshFieldInput {
 public:
  FaceAreaFieldInput() : bke::MeshFieldInput(CPPType::get<float>(), "Face Area Field")
  {
    category_ = Category::Generated;
  }
 
  GVArray get_varray_for_context(const Mesh &mesh,
                                 const AttrDomain domain,
                                 const IndexMask & /*mask*/) const final
  {
    return construct_face_area_varray(mesh, domain);
  }
 
  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;
  }
 
  std::optional<AttrDomain> preferred_domain(const Mesh & /*mesh*/) const override
  {
    return AttrDomain::Face;
  }
};
 
static void node_geo_exec(GeoNodeExecParams params)
{
  params.set_output("Area", Field<float>(std::make_shared<FaceAreaFieldInput>()));
}
 
static void node_register()
{
  static blender::bke::bNodeType ntype;
  geo_node_type_base(&ntype, "GeometryNodeInputMeshFaceArea", GEO_NODE_INPUT_MESH_FACE_AREA);
  ntype.ui_name = "Face Area";
  ntype.ui_description = "Calculate the surface area of a mesh's faces";
  ntype.enum_name_legacy = "MESH_FACE_AREA";
  ntype.nclass = NODE_CLASS_INPUT;
  ntype.declare = node_declare;
  ntype.geometry_node_execute = node_geo_exec;
  blender::bke::node_register_type(ntype);
}
NOD_REGISTER_NODE(node_register)
 
}  // namespace blender::nodes::node_geo_input_mesh_face_area_cc