Geometry Nodes: Spline Length Input Node

The Spline Length Input node provides a field containing the
length of the current evaluated spline to the Point and Spline
domains.

Differential Revision: https://developer.blender.org/D12706

release/scripts/startup/nodeitems_builtins.py

@@ -525,6 +525,7 @@ geometry_node_categories = [
         NodeItem("GeometryNodeCurveFill"),
         NodeItem("GeometryNodeCurveTrim"),
         NodeItem("GeometryNodeCurveLength"),
+        NodeItem("GeometryNodeSplineLength"),
         NodeItem("GeometryNodeCurveSubdivide"),
         NodeItem("GeometryNodeCurveParameter"),
         NodeItem("GeometryNodeInputTangent"),

source/blender/blenkernel/BKE_node.h

@@ -1508,8 +1508,9 @@ int ntreeTexExecTree(struct bNodeTree *ntree,
 #define GEO_NODE_POINTS_TO_VERTICES 1094
 #define GEO_NODE_CURVE_REVERSE 1095
 #define GEO_NODE_PROXIMITY 1096
-
 #define GEO_NODE_CURVE_SUBDIVIDE 1097
+#define GEO_NODE_INPUT_SPLINE_LENGTH 1098
+
 /** \} */
 
 /* -------------------------------------------------------------------- */

source/blender/blenkernel/intern/node.cc

@@ -5767,6 +5767,7 @@ static void registerGeometryNodes()
   register_node_type_geo_input_normal();
   register_node_type_geo_input_position();
   register_node_type_geo_input_tangent();
+  register_node_type_geo_input_spline_length();
   register_node_type_geo_instance_on_points();
   register_node_type_geo_is_viewport();
   register_node_type_geo_join_geometry();

source/blender/nodes/CMakeLists.txt

@@ -217,6 +217,7 @@ set(SRC
   geometry/nodes/node_geo_input_material.cc
   geometry/nodes/node_geo_input_normal.cc
   geometry/nodes/node_geo_input_position.cc
+  geometry/nodes/node_geo_input_spline_length.cc
   geometry/nodes/node_geo_input_tangent.cc
   geometry/nodes/node_geo_instance_on_points.cc
   geometry/nodes/node_geo_is_viewport.cc

source/blender/nodes/NOD_geometry.h

@@ -86,6 +86,7 @@ void register_node_type_geo_input_index(void);
 void register_node_type_geo_input_material(void);
 void register_node_type_geo_input_normal(void);
 void register_node_type_geo_input_position(void);
+void register_node_type_geo_input_spline_length(void);
 void register_node_type_geo_input_tangent(void);
 void register_node_type_geo_instance_on_points(void);
 void register_node_type_geo_is_viewport(void);

source/blender/nodes/NOD_static_types.h

@@ -345,6 +345,7 @@ DefNode(GeometryNode, GEO_NODE_INPUT_INDEX, 0, "INDEX", InputIndex, "Index", "")
 DefNode(GeometryNode, GEO_NODE_INPUT_MATERIAL, def_geo_input_material, "INPUT_MATERIAL", InputMaterial, "Material", "")
 DefNode(GeometryNode, GEO_NODE_INPUT_NORMAL, 0, "INPUT_NORMAL", InputNormal, "Normal", "")
 DefNode(GeometryNode, GEO_NODE_INPUT_POSITION, 0, "POSITION", InputPosition, "Position", "")
+DefNode(GeometryNode, GEO_NODE_INPUT_SPLINE_LENGTH, 0, "SPLINE_LENGTH", SplineLength, "Spline Length", "")
 DefNode(GeometryNode, GEO_NODE_INPUT_TANGENT, 0, "INPUT_TANGENT", InputTangent, "Curve Tangent", "")
 DefNode(GeometryNode, GEO_NODE_INSTANCE_ON_POINTS, 0, "INSTANCE_ON_POINTS", InstanceOnPoints, "Instance on Points", "")
 DefNode(GeometryNode, GEO_NODE_IS_VIEWPORT, 0, "IS_VIEWPORT", IsViewport, "Is Viewport", "")

source/blender/nodes/geometry/nodes/node_geo_input_spline_length.cc

@@ -0,0 +1,109 @@
+/*
+ * 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 "node_geometry_util.hh"
+
+#include "BKE_spline.hh"
+
+namespace blender::nodes {
+
+static void geo_node_input_spline_length_declare(NodeDeclarationBuilder &b)
+{
+  b.add_output<decl::Float>("Length").field_source();
+}
+
+static const GVArray *construct_spline_length_gvarray(const CurveComponent &component,
+                                                      const AttributeDomain domain,
+                                                      ResourceScope &scope)
+{
+  const CurveEval *curve = component.get_for_read();
+  if (curve == nullptr) {
+    return nullptr;
+  }
+
+  Span<SplinePtr> splines = curve->splines();
+  auto length_fn = [splines](int i) { return splines[i]->length(); };
+
+  if (domain == ATTR_DOMAIN_CURVE) {
+    return &scope.construct<
+        fn::GVArray_For_EmbeddedVArray<float, VArray_For_Func<float, decltype(length_fn)>>>(
+        splines.size(), splines.size(), length_fn);
+  }
+  if (domain == ATTR_DOMAIN_POINT) {
+    GVArrayPtr length = std::make_unique<
+        fn::GVArray_For_EmbeddedVArray<float, VArray_For_Func<float, decltype(length_fn)>>>(
+        splines.size(), splines.size(), length_fn);
+    return scope
+        .add_value(component.attribute_try_adapt_domain(
+            std::move(length), ATTR_DOMAIN_CURVE, ATTR_DOMAIN_POINT))
+        .get();
+  }
+
+  return nullptr;
+}
+
+class SplineLengthFieldInput final : public fn::FieldInput {
+ public:
+  SplineLengthFieldInput() : fn::FieldInput(CPPType::get<float>(), "Spline Length")
+  {
+  }
+
+  const GVArray *get_varray_for_context(const fn::FieldContext &context,
+                                        IndexMask UNUSED(mask),
+                                        ResourceScope &scope) const final
+  {
+    if (const GeometryComponentFieldContext *geometry_context =
+            dynamic_cast<const GeometryComponentFieldContext *>(&context)) {
+
+      const GeometryComponent &component = geometry_context->geometry_component();
+      const AttributeDomain domain = geometry_context->domain();
+      if (component.type() == GEO_COMPONENT_TYPE_CURVE) {
+        const CurveComponent &curve_component = static_cast<const CurveComponent &>(component);
+        return construct_spline_length_gvarray(curve_component, domain, scope);
+      }
+    }
+    return nullptr;
+  }
+
+  uint64_t hash() const override
+  {
+    /* Some random constant hash. */
+    return 3549623580;
+  }
+
+  bool is_equal_to(const fn::FieldNode &other) const override
+  {
+    return dynamic_cast<const SplineLengthFieldInput *>(&other) != nullptr;
+  }
+};
+
+static void geo_node_input_spline_length_exec(GeoNodeExecParams params)
+{
+  Field<float> length_field{std::make_shared<SplineLengthFieldInput>()};
+  params.set_output("Length", std::move(length_field));
+}
+
+}  // namespace blender::nodes
+
+void register_node_type_geo_input_spline_length()
+{
+  static bNodeType ntype;
+
+  geo_node_type_base(&ntype, GEO_NODE_INPUT_SPLINE_LENGTH, "Spline Length", NODE_CLASS_INPUT, 0);
+  ntype.geometry_node_execute = blender::nodes::geo_node_input_spline_length_exec;
+  ntype.declare = blender::nodes::geo_node_input_spline_length_declare;
+  nodeRegisterType(&ntype);
+}