Geometry Nodes: Curve and mesh topology access nodes

This patch contains an initial set of nodes to access basic
mesh topology information, as explored in T100020.

The nodes allow six direct topology mappings for meshes:
- **Corner -> Face** The face a corner is in, the index in the face
- **Vertex -> Edge** Choose an edge attached to the vertex
- **Vertex -> Corner** Choose a corner attached to the vertex
- **Corner -> Edge** The next and previous edge at each face corner
- **Corner -> Vertex** The vertex associated with a corner
- **Corner -> Corner** Offset a corner index within a face

And two new topology mappings for curves:
- **Curve -> Points** Choose a point within a curve
- **Point -> Curve** The curve a point is in, the index in the curve

The idea is that some of the 16 possible mesh mappings are more
important, and that this is a useful set of nodes to start exploring
this area. For mappings with an arbitrary number of connections, we
must sort them and use an index to choose a single element, because
geometry nodes does not support list fields. Note that the sort
index has repeating behavior as it goes over the "Total" number of
connections, and negative sort indices choose from the end.

Currently which of the "start" elements is used is determined by the
field context, so the "Field at Index" and "Interpolate Domain" nodes
will be quite important. Also, currently the "Sort Index" inputs are
clamped to the number of connections.

One important feature that isn't implemented here is using the winding
order for the output elements. This can be a separate mode for some
of these nodes. It will be optional because of the performance impact.

There are several todos for separate commits after this:
- Rename "Control Point Neighbors" to be consistent with this naming
- Version away the "Vertex Neighbors" node which is fully redundant now
- Implement a special case for when no weights are used for performance
- De-duplicating some of the sorting logic between the nodes
- Improve performance and memory use of topology mappings
- Look into caching some of the mappings on meshes

Differential Revision: https://developer.blender.org/D16029

1 files changed, 9 insertions, 0 deletions

diff --git a/source/blender/nodes/NOD_geometry.h b/source/blender/nodes/NOD_geometry.h
index 4ead6326295..7916bb6d08c 100644
--- a/source/blender/nodes/NOD_geometry.h
+++ b/source/blender/nodes/NOD_geometry.h
@@ -46,6 +46,8 @@ void register_node_type_geo_curve_spline_type(void);
 void register_node_type_geo_curve_subdivide(void);
 void register_node_type_geo_curve_to_mesh(void);
 void register_node_type_geo_curve_to_points(void);
+void register_node_type_geo_curve_topology_curve_of_point(void);
+void register_node_type_geo_curve_topology_points_of_curve(void);
 void register_node_type_geo_curve_trim(void);
 void register_node_type_geo_deform_curves_on_surface(void);
 void register_node_type_geo_delete_geometry(void);
@@ -110,6 +112,13 @@ void register_node_type_geo_mesh_subdivide(void);
 void register_node_type_geo_mesh_to_curve(void);
 void register_node_type_geo_mesh_to_points(void);
 void register_node_type_geo_mesh_to_volume(void);
+void register_node_type_geo_mesh_topology_corners_of_face(void);
+void register_node_type_geo_mesh_topology_corners_of_vertex(void);
+void register_node_type_geo_mesh_topology_edges_of_corner(void);
+void register_node_type_geo_mesh_topology_edges_of_vertex(void);
+void register_node_type_geo_mesh_topology_face_of_corner(void);
+void register_node_type_geo_mesh_topology_offset_corner_in_face(void);
+void register_node_type_geo_mesh_topology_vertex_of_corner(void);
 void register_node_type_geo_object_info(void);
 void register_node_type_geo_points_to_vertices(void);
 void register_node_type_geo_points_to_volume(void);