vertex attribute cosumer/ providers

[paroj]

Some SRS stages might want to access the same vertex attribute, e.g. TEXCOORD0.

Other SRS stages do provide it by different means, e.g. by computing it.

Currently the consumers check whether somebody already provides it via probing for it with get:

getOutputParameter(Parameter::SPC_TEXTURE_COORDINATE0, GCT_FLOAT2)

If this fails, they fall back to a minimal pass-through in the vertex shader.

However, this only works if the provider was executed before e.g. if FFP_LIGHTING cannot query for FFP_TEXTURING as the latter is only executed afterwards.

Also, TEXCOORD0 may mean different things between SRS. E.g. TEXTURING may apply a texture matrix to TEXCOORD0 for the albedo layer. However, the LIGHTING would use TEXCOORD0 to read a specular map. Should we enforce that both are the same?
Should we add more SPC to make them unique?

• swap LIGHTING and TEXTURING order?
• add a matching phase, where SRS may advertise what they provide/ want to consume?