skRendered (shader module)

The frame as it entered the style stack, for blocks that list rendered under reads and declare sk_rendered after the shared header. sk_rendered_at(uv) returns it in display code values. Use it for what the renderer said, not what earlier blocks made of it: a light estimate against sk_albedo (texture cancels out), or an original colour to restore. Costs one copy of the frame per frame, shared by every block that reads it (and by excluded objects).