Material constants (a.k.a: specialization constants) can only be set
during Material creation through Material::Builder.
This change somewhat relaxes that limitation by allowing constants to
be set at runtime on Material directly.
Currently this new API is still private and only supported on FMaterial.
This feature works by invalidating the HwProgram cache of the concerned
Material, causing a shader recompile per variant; so this API is costly
and should be used only for debugging or during app/game configuration.
The TAA material is modified to use constants instead of #defines for
various settings and those are exposed in TaaOptions as well is in
ViewerGui. So with this change all aspects of the TAA material can
be changed at runtime.
2a67152dda
