Currently lookup of Object and Instancer attributes is completely
duplicated between Cycles, Eevee and Eevee Next. This is bad design,
so this patch aims to deduplicate it by introducing a common API
in blenkernel.
In case of Cycles this requires certain hacks, but according to
Brecht it is planned to be rewritten later for more direct access
to internal Blender data anyway.
Differential Revision: https://developer.blender.org/D16117
This replaces the direct shader uniform layout declaration by a linear
search through a global buffer.
Each instance has an attribute offset inside the global buffer and an
attribute count.
This removes any padding and tighly pack all uniform attributes inside
a single buffer.
This would also remove the limit of 8 attribute but it is kept because of
compatibility with the old system that is still used by the old draw
manager.
