Geometry Nodes: fields and anonymous attributes

This implements the initial core framework for fields and anonymous
attributes (also see T91274).

The new functionality is hidden behind the "Geometry Nodes Fields"
feature flag. When enabled in the user preferences, the following
new nodes become available: `Position`, `Index`, `Normal`,
`Set Position` and `Attribute Capture`.

Socket inspection has not been updated to work with fields yet.

Besides these changes at the user level, this patch contains the
ground work for:
* building and evaluating fields at run-time (`FN_fields.hh`) and
* creating and accessing anonymous attributes on geometry
  (`BKE_anonymous_attribute.h`).

For evaluating fields we use a new so called multi-function procedure
(`FN_multi_function_procedure.hh`). It allows composing multi-functions
in arbitrary ways and supports efficient evaluation as is required by
fields. See `FN_multi_function_procedure.hh` for more details on how
this evaluation mechanism can be used.

A new `AttributeIDRef` has been added which allows handling named
and anonymous attributes in the same way in many places.

Hans and I worked on this patch together.

Differential Revision: https://developer.blender.org/D12414

1 files changed, 5 insertions, 0 deletions

diff --git a/source/blender/nodes/NOD_geometry.h b/source/blender/nodes/NOD_geometry.h
index 00062400eee..e9fb4ad123c 100644
--- a/source/blender/nodes/NOD_geometry.h
+++ b/source/blender/nodes/NOD_geometry.h
@@ -37,6 +37,7 @@ void register_node_type_geo_attribute_compare(void);
 void register_node_type_geo_attribute_convert(void);
 void register_node_type_geo_attribute_curve_map(void);
 void register_node_type_geo_attribute_fill(void);
+void register_node_type_geo_attribute_capture(void);
 void register_node_type_geo_attribute_map_range(void);
 void register_node_type_geo_attribute_math(void);
 void register_node_type_geo_attribute_mix(void);
@@ -71,7 +72,10 @@ void register_node_type_geo_curve_to_points(void);
 void register_node_type_geo_curve_trim(void);
 void register_node_type_geo_delete_geometry(void);
 void register_node_type_geo_edge_split(void);
+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_is_viewport(void);
 void register_node_type_geo_join_geometry(void);
 void register_node_type_geo_material_assign(void);
@@ -99,6 +103,7 @@ void register_node_type_geo_sample_texture(void);
 void register_node_type_geo_select_by_handle_type(void);
 void register_node_type_geo_select_by_material(void);
 void register_node_type_geo_separate_components(void);
+void register_node_type_geo_set_position(void);
 void register_node_type_geo_subdivision_surface(void);
 void register_node_type_geo_switch(void);
 void register_node_type_geo_transform(void);