Geometry Nodes: Curve Set Spline Type

This node sets the selected (or all) splines in curve to a chosen target
spline type. Poly, Bezier, and NURB splines can be converted to any of
the other types. This is meant to be a building block node, useful in
many procedural situations.

In the future the node could be optimized with multi-threading, or by
avoiding copying in many cases, either by retrieving the curve for write
access or by passing the raw vectors to the new splines where possible.

With edits from Hans Goudey (@HooglyBoogly)

Differential Revision: https://developer.blender.org/D12013

source/blender/blenkernel/BKE_node.h

@@ -1475,6 +1475,7 @@ int ntreeTexExecTree(struct bNodeTree *ntree,
 #define GEO_NODE_CURVE_PRIMITIVE_QUADRILATERAL 1070
 #define GEO_NODE_CURVE_TRIM 1071
 #define GEO_NODE_CURVE_SET_HANDLES 1072
+#define GEO_NODE_CURVE_SPLINE_TYPE 1073
 
 /** \} */