Geometry Nodes: Face is Planar Node

This adds a node with a boolean field output which returns true if all of the
points of the evaluated face are on the same plane. A float field input allows
for the threshold of the face/point comparison to be adjusted on a per face basis.

One clear use case is to only triangulate faces that are not planar.

Differential Revision: https://developer.blender.org/D13906

release/scripts/startup/nodeitems_builtins.py

@@ -142,6 +142,7 @@ def mesh_node_items(context):
     yield NodeItem("GeometryNodeInputMeshEdgeVertices")
     yield NodeItem("GeometryNodeInputMeshFaceArea")
     yield NodeItem("GeometryNodeInputMeshFaceNeighbors")
+    yield NodeItem("GeometryNodeInputMeshFaceIsPlanar")
     yield NodeItem("GeometryNodeInputMeshIsland")
     yield NodeItem("GeometryNodeInputShadeSmooth")
     yield NodeItem("GeometryNodeInputMeshVertexNeighbors")

source/blender/blenkernel/BKE_node.h

@@ -1515,6 +1515,7 @@ struct TexResult;
 #define GEO_NODE_EXTRUDE_MESH 1152
 #define GEO_NODE_MERGE_BY_DISTANCE 1153
 #define GEO_NODE_DUPLICATE_ELEMENTS 1154
+#define GEO_NODE_INPUT_MESH_FACE_IS_PLANAR 1155
 
 /** \} */
 

source/blender/blenkernel/intern/node.cc

@@ -4770,6 +4770,7 @@ static void registerGeometryNodes()
   register_node_type_geo_input_mesh_edge_neighbors();
   register_node_type_geo_input_mesh_edge_vertices();
   register_node_type_geo_input_mesh_face_area();
+  register_node_type_geo_input_mesh_face_is_planar();
   register_node_type_geo_input_mesh_face_neighbors();
   register_node_type_geo_input_mesh_island();
   register_node_type_geo_input_mesh_vertex_neighbors();

source/blender/nodes/NOD_geometry.h

@@ -101,6 +101,7 @@ void register_node_type_geo_input_mesh_edge_angle(void);
 void register_node_type_geo_input_mesh_edge_neighbors(void);
 void register_node_type_geo_input_mesh_edge_vertices(void);
 void register_node_type_geo_input_mesh_face_area(void);
+void register_node_type_geo_input_mesh_face_is_planar(void);
 void register_node_type_geo_input_mesh_face_neighbors(void);
 void register_node_type_geo_input_mesh_island(void);
 void register_node_type_geo_input_mesh_vertex_neighbors(void);

source/blender/nodes/NOD_static_types.h

@@ -359,6 +359,7 @@ DefNode(GeometryNode, GEO_NODE_INPUT_MESH_EDGE_ANGLE, 0, "MESH_EDGE_ANGLE", Inpu
 DefNode(GeometryNode, GEO_NODE_INPUT_MESH_EDGE_NEIGHBORS, 0, "MESH_EDGE_NEIGHBORS", InputMeshEdgeNeighbors, "Edge Neighbors", "")
 DefNode(GeometryNode, GEO_NODE_INPUT_MESH_EDGE_VERTICES, 0, "MESH_EDGE_VERTICES", InputMeshEdgeVertices, "Edge Vertices", "")
 DefNode(GeometryNode, GEO_NODE_INPUT_MESH_FACE_AREA, 0, "MESH_FACE_AREA", InputMeshFaceArea, "Face Area", "")
+DefNode(GeometryNode, GEO_NODE_INPUT_MESH_FACE_IS_PLANAR, 0, "MESH_FACE_IS_PLANAR", InputMeshFaceIsPlanar, "Face is Planar", "")
 DefNode(GeometryNode, GEO_NODE_INPUT_MESH_FACE_NEIGHBORS, 0, "MESH_FACE_NEIGHBORS", InputMeshFaceNeighbors, "Face Neighbors", "")
 DefNode(GeometryNode, GEO_NODE_INPUT_MESH_ISLAND, 0, "MESH_ISLAND", InputMeshIsland, "Mesh Island", "")
 DefNode(GeometryNode, GEO_NODE_INPUT_MESH_VERTEX_NEIGHBORS, 0, "MESH_VERTEX_NEIGHBORS", InputMeshVertexNeighbors, "Vertex Neighbors", "")

source/blender/nodes/geometry/CMakeLists.txt

@@ -117,6 +117,7 @@ set(SRC
   nodes/node_geo_input_mesh_edge_neighbors.cc
   nodes/node_geo_input_mesh_edge_vertices.cc
   nodes/node_geo_input_mesh_face_area.cc
+  nodes/node_geo_input_mesh_face_is_planar.cc
   nodes/node_geo_input_mesh_face_neighbors.cc
   nodes/node_geo_input_mesh_island.cc
   nodes/node_geo_input_mesh_vertex_neighbors.cc

source/blender/nodes/geometry/nodes/node_geo_input_mesh_face_is_planar.cc

@@ -0,0 +1,116 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+
+#include "DNA_mesh_types.h"
+#include "DNA_meshdata_types.h"
+#include "node_geometry_util.hh"
+
+namespace blender::nodes::node_geo_input_mesh_face_is_planar_cc {
+
+static void node_declare(NodeDeclarationBuilder &b)
+{
+  b.add_input<decl::Float>("Threshold")
+      .field_source()
+      .default_value(0.01f)
+      .subtype(PROP_DISTANCE)
+      .supports_field()
+      .description(N_("The distance a point can be from the surface before the face is no longer "
+                      "considered planar"))
+      .min(0.0f);
+  b.add_output<decl::Bool>("Planar").field_source();
+}
+
+class PlanarFieldInput final : public GeometryFieldInput {
+ private:
+  Field<float> threshold_;
+
+ public:
+  PlanarFieldInput(Field<float> threshold)
+      : GeometryFieldInput(CPPType::get<bool>(), "Planar"), threshold_(threshold)
+  {
+    category_ = Category::Generated;
+  }
+
+  GVArray get_varray_for_context(const GeometryComponent &component,
+                                 const AttributeDomain domain,
+                                 [[maybe_unused]] IndexMask mask) const final
+  {
+    if (component.type() != GEO_COMPONENT_TYPE_MESH) {
+      return {};
+    }
+
+    const MeshComponent &mesh_component = static_cast<const MeshComponent &>(component);
+    const Mesh *mesh = mesh_component.get_for_read();
+    if (mesh == nullptr) {
+      return {};
+    }
+
+    GeometryComponentFieldContext context{mesh_component, ATTR_DOMAIN_FACE};
+    fn::FieldEvaluator evaluator{context, mesh->totpoly};
+    evaluator.add(threshold_);
+    evaluator.evaluate();
+    const VArray<float> &thresholds = evaluator.get_evaluated<float>(0);
+
+    Span<float3> poly_normals{(float3 *)BKE_mesh_poly_normals_ensure(mesh), mesh->totpoly};
+
+    auto planar_fn = [mesh, thresholds, poly_normals](const int i_poly) -> bool {
+      if (mesh->mpoly[i_poly].totloop <= 3) {
+        return true;
+      }
+      const int loopstart = mesh->mpoly[i_poly].loopstart;
+      const int loops = mesh->mpoly[i_poly].totloop;
+      Span<MLoop> poly_loops(&mesh->mloop[loopstart], loops);
+      float3 reference_normal = poly_normals[i_poly];
+
+      float min = FLT_MAX;
+      float max = FLT_MIN;
+
+      for (const int i_loop : poly_loops.index_range()) {
+        const float3 vert = mesh->mvert[poly_loops[i_loop].v].co;
+        float dot = math::dot(reference_normal, vert);
+        if (dot > max) {
+          max = dot;
+        }
+        if (dot < min) {
+          min = dot;
+        }
+      }
+      return max - min < thresholds[i_poly] / 2.0f;
+    };
+
+    return component.attribute_try_adapt_domain<bool>(
+        VArray<bool>::ForFunc(mesh->totpoly, planar_fn), ATTR_DOMAIN_FACE, domain);
+  }
+
+  uint64_t hash() const override
+  {
+    /* Some random constant hash. */
+    return 2356235652;
+  }
+
+  bool is_equal_to(const fn::FieldNode &other) const override
+  {
+    return dynamic_cast<const PlanarFieldInput *>(&other) != nullptr;
+  }
+};
+
+static void geo_node_exec(GeoNodeExecParams params)
+{
+  Field<float> threshold = params.extract_input<Field<float>>("Threshold");
+  Field<bool> planar_field{std::make_shared<PlanarFieldInput>(threshold)};
+  params.set_output("Planar", std::move(planar_field));
+}
+
+}  // namespace blender::nodes::node_geo_input_mesh_face_is_planar_cc
+
+void register_node_type_geo_input_mesh_face_is_planar()
+{
+  namespace file_ns = blender::nodes::node_geo_input_mesh_face_is_planar_cc;
+
+  static bNodeType ntype;
+
+  geo_node_type_base(
+      &ntype, GEO_NODE_INPUT_MESH_FACE_IS_PLANAR, "Face is Planar", NODE_CLASS_INPUT);
+  ntype.geometry_node_execute = file_ns::geo_node_exec;
+  ntype.declare = file_ns::node_declare;
+  nodeRegisterType(&ntype);
+}