MSL does not have an implicit global scope, this is emulated via macro's adding an indirection for uniforms, attributes, shader stage inputs and outputs such as:
#define roughness shaderinst->roughness.
Variables in GLSL which exist within uniform blocks can be directly referenced via the global scope, unlike standard C++. This means that variable name pollution occurs if subsequent local variables in the code use the same name, resulting in compilation errors.
A number of these conflicting names have been renamed to ensure unique naming and no further scope pollution.
Ref T96261
Reviewed By: fclem
Maniphest Tasks: T96261
Differential Revision: https://developer.blender.org/D14452
Also adds a few things to GPUShader for easily create shaders.
Heavy usage of macros to compose the createInfo and avoid
duplications and copy paste bugs.
This makes the link between the shader request functions
(in workbench_shader.cc) and the actual createInfo a bit
obscure since the names are composed and not searchable.
Reviewed By: jbakker
Differential Revision: https://developer.blender.org/D13910
