Geometry Nodes: Add "Set Curve Order" node

Adds a dedicated node to set the order of NURBS curves.
Design at #154612

Pull Request: https://projects.blender.org/blender/blender/pulls/154648

scripts/startup/bl_ui/node_add_menu_geometry.py

@@ -97,6 +97,7 @@ class NODE_MT_gn_curve_write_base(node_add_menu.NodeMenu):
     def draw(self, _context):
         layout = self.layout
         self.node_operator(layout, "GeometryNodeSetCurveNormal")
+        self.node_operator(layout, "GeometryNodeSetCurveOrder")
         self.node_operator(layout, "GeometryNodeSetCurveRadius")
         self.node_operator(layout, "GeometryNodeSetCurveTilt")
         self.node_operator(layout, "GeometryNodeSetCurveHandlePositions")

source/blender/makesrna/intern/rna_nodetree.cc

@@ -10385,6 +10385,7 @@ static void rna_def_nodes(BlenderRNA *brna)
   define("GeometryNode", "GeometryNodeSeparateGeometry");
   define("GeometryNode", "GeometryNodeSetCurveHandlePositions");
   define("GeometryNode", "GeometryNodeSetCurveNormal");
+  define("GeometryNode", "GeometryNodeSetCurveOrder");
   define("GeometryNode", "GeometryNodeSetCurveRadius");
   define("GeometryNode", "GeometryNodeSetCurveTilt");
   define("GeometryNode", "GeometryNodeSetGeometryBundle");

source/blender/nodes/geometry/CMakeLists.txt

@@ -233,6 +233,7 @@ set(SRC
   nodes/node_geo_separate_geometry.cc
   nodes/node_geo_set_curve_handles.cc
   nodes/node_geo_set_curve_normal.cc
+  nodes/node_geo_set_curve_order.cc
   nodes/node_geo_set_curve_radius.cc
   nodes/node_geo_set_curve_tilt.cc
   nodes/node_geo_set_geometry_bundle.cc

source/blender/nodes/geometry/nodes/node_geo_set_curve_order.cc

@@ -0,0 +1,110 @@
+/* SPDX-FileCopyrightText: 2026 Blender Authors
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later */
+
+#include "BKE_curves.hh"
+#include "BKE_grease_pencil.hh"
+#include "BKE_type_conversions.hh"
+
+#include "FN_multi_function_builder.hh"
+
+#include "GEO_foreach_geometry.hh"
+
+#include "node_geometry_util.hh"
+
+namespace blender::nodes::node_geo_set_curve_order_cc {
+
+static void node_declare(NodeDeclarationBuilder &b)
+{
+  b.use_custom_socket_order();
+  b.allow_any_socket_order();
+  b.add_input<decl::Geometry>("Curves")
+      .supported_type({GeometryComponent::Type::Curve, GeometryComponent::Type::GreasePencil})
+      .description("Curves to change the order of");
+  b.add_output<decl::Geometry>("Curves").propagate_all().align_with_previous();
+  b.add_input<decl::Bool>("Selection").default_value(true).hide_value().field_on_all();
+  b.add_input<decl::Int>("Order").default_value(4).min(2).max(127).field_on_all();
+}
+
+static void set_grease_pencil_order(GreasePencil &grease_pencil,
+                                    const Field<bool> &selection,
+                                    const Field<int8_t> &order,
+                                    std::atomic<bool> &has_nurbs)
+{
+  using namespace blender::bke::greasepencil;
+  for (const int layer_index : grease_pencil.layers().index_range()) {
+    Drawing *drawing = grease_pencil.get_eval_drawing(grease_pencil.layer(layer_index));
+    if (drawing == nullptr) {
+      continue;
+    }
+    bke::CurvesGeometry &curves = drawing->strokes_for_write();
+    if (curves.has_curve_with_type(CURVE_TYPE_NURBS)) {
+      bke::try_capture_field_on_geometry(
+          curves.attributes_for_write(),
+          bke::GreasePencilLayerFieldContext(grease_pencil, AttrDomain::Curve, layer_index),
+          "nurbs_order",
+          bke::AttrDomain::Curve,
+          selection,
+          order);
+      has_nurbs = true;
+    }
+    else {
+      continue;
+    }
+  }
+}
+
+static void node_geo_exec(GeoNodeExecParams params)
+{
+  GeometrySet geometry_set = params.extract_input<GeometrySet>("Curves");
+  const Field<bool> selection = params.extract_input<Field<bool>>("Selection");
+  const Field<int> order = params.extract_input<Field<int>>("Order");
+
+  const bke::DataTypeConversions &conversions = bke::get_implicit_type_conversions();
+  const Field<int8_t> order_int8 = conversions.try_convert(order, CPPType::get<int8_t>());
+
+  std::atomic<bool> has_nurbs = false;
+
+  geometry::foreach_real_geometry(geometry_set, [&](GeometrySet &geometry_set) {
+    if (Curves *curves_id = geometry_set.get_curves_for_write()) {
+      bke::CurvesGeometry &curves = curves_id->geometry.wrap();
+      if (curves.has_curve_with_type(CURVE_TYPE_NURBS)) {
+        const bke::CurvesFieldContext field_context{*curves_id, AttrDomain::Curve};
+        bke::try_capture_field_on_geometry(curves.attributes_for_write(),
+                                           field_context,
+                                           "nurbs_order",
+                                           bke::AttrDomain::Curve,
+                                           selection,
+                                           order_int8);
+        has_nurbs = true;
+      }
+    }
+    if (GreasePencil *grease_pencil = geometry_set.get_grease_pencil_for_write()) {
+      set_grease_pencil_order(*grease_pencil, selection, order_int8, has_nurbs);
+    }
+  });
+
+  if (!has_nurbs) {
+    params.error_message_add(NodeWarningType::Info, TIP_("Input curves do not have NURBS type"));
+  }
+
+  params.set_output("Curves", std::move(geometry_set));
+}
+
+static void node_register()
+{
+  static bke::bNodeType ntype;
+
+  geo_node_type_base(&ntype, "GeometryNodeSetCurveOrder");
+  ntype.ui_name = "Set Curve Order";
+  ntype.ui_description =
+      "Control how many control points influence each evaluated point by changing the "
+      "\"nurbs_order\" attribute";
+  ntype.nclass = NODE_CLASS_GEOMETRY;
+  ntype.geometry_node_execute = node_geo_exec;
+  ntype.declare = node_declare;
+  bke::node_register_type(ntype);
+}
+NOD_REGISTER_NODE(node_register)
+
+}  // namespace blender::nodes::node_geo_set_curve_order_cc