These implementations remove dependency on the Geometry pass by instead invoking one vertex shader instance for each expected output vertex, matching what a geometry shader would emit. Each vertex shader instance is then responsible for calculating the same output position based on its vertex_id as the logic would in the geometry shader version.
SSBO Vertex fetch enables full random-access into a vertex buffer by binding it as a read-only SSBO. This enables each instance to read neighbouring vertex data to perform contextual calculations as a geometry shader would, for cases where attribute Multiload is not supported.
Authored by Apple: Michael Parkin-White
Ref T96261
Reviewed By: fclem
Differential Revision: https://developer.blender.org/D15901
1514e1a5b7