Geometry Nodes: Add "normal" attribute for face normals

This commit adds a `normal` attribute on the polygon domain. Since
normal data is derived data purely based off of the location of each
face's vertices, it is exposed as a read-only attribute. After
rB80f7f1070f17, this attribute can be interpolated to the other domains.

Since this attribute is a special case compared to the others, the
implementation subclasses `BuiltinAttributeProvider`. It's possible
there is a better way to abstract this. Something else might also
become apparent if we add similar read-only attributes.

See rB2966871a7a891bf36 for why this is preferred over the previous
implementation.

Differential Revision: https://developer.blender.org/D10677

1 files changed, 1 insertions, 1 deletions

diff --git a/source/blender/blenkernel/intern/geometry_set_instances.cc b/source/blender/blenkernel/intern/geometry_set_instances.cc
index 70b48a253ed..fc9d793c119 100644
--- a/source/blender/blenkernel/intern/geometry_set_instances.cc
+++ b/source/blender/blenkernel/intern/geometry_set_instances.cc
@@ -381,7 +381,7 @@ static void join_instance_groups_mesh(Span<GeometryInstanceGroup> set_groups,
   gather_attribute_info(attributes,
                         component_types,
                         set_groups,
-                        {"position", "material_index", "vertex_normal", "shade_smooth"});
+                        {"position", "material_index", "normal", "shade_smooth"});
   join_attributes(
       set_groups, component_types, attributes, static_cast<GeometryComponent &>(dst_component));
 }