Hardware Oddity Texture Stage Dependencies

Texture-stage dependencies

Evidence: NVIDIA-family specification, not yet an Xbox measurement. The NV_texture_shader specification describes an exception to simple left-to-right evaluation: in a diffuse/reflection cube-map pairing, the stage-2 cube-map lookup depends on a dot product from stage 3. It also distinguishes a stage's texture-shader intermediate from its RGBA result for register combiners; the documented DOT_PRODUCT operation has a floating-point intermediate while its RGBA result is zero.

An all-black stage thumbnail therefore does not prove that the stage contributed nothing. A preview should show the dependency graph and the two output kinds, while retaining the raw method sequence.

Proposed test: trace the corresponding NV2A setup, then vary the stage-3 dot-product inputs and observe the stage-2 lookup and combiner input independently. Until that test, keep the Xbox applicability labeled as a target rather than a verified silicon fact.

See also NV2A Graphics Architecture and Shrek's HILO_1 path.