GXSetTevKAlphaSel (HW2)

• Category: Texture Environment
• Matrix Status: Implemented
• Matrix Notes: Implemented per-stage konst-alpha selector state with BP-field-width masking (5-bit).
• Matrix Link: Gfx-GX-API-Matrix

Official SDK (Reference)

• Manual page: reference/man/gfx/gx/Tev/GXSetTevKAlphaSel.html
• SDK source: reference/ACGC-PC-Port/src/static/dolphin/gx/GXTev.c (GXSetTevKAlphaSel)
• SDK behavior:
  • HW2-only API selecting konst alpha source for one TEV stage.
  • Selector is written as a 5-bit field into tevKsel BP register.
  • SDK debug path checks GX-begin and asserts stage < 16.

libPorpoise Implementation

• Public API declaration: include/dolphin/gx/GXTev.h
• Runtime implementation: src/gx/pc_gx.c (GXSetTevKAlphaSel)
• Shader consumption:
  • Stage selectors uploaded via u_tev_ksel[] from pc_gx.c.
  • Interpreted in src/gx/shaders/default.frag (getKonstA) when GX_CA_KONST is used.
• Behavior:
  • Stores per-stage selector and marks TEV-stage state dirty.
  • Applies sel & 0x1F mask to mirror SDK BP-field width.
  • Guards writes with stage < 16.

SDK vs Porpoise Diff

• Signature parity:
  • Signatures match (GXTevStageID, GXTevKAlphaSel).
• Behavioral parity:
  • Per-stage konst-alpha selector behavior is implemented and used in TEV shader path.
  • Selector bit-width semantics now match hardware field width.
• Known divergence:
  • SDK writes packed BP register state directly; Porpoise stores decoded state and evaluates in shader.

Validation Checklist

• GX demo coverage checked
• Pikmin usage path checked
• Matrix status updated if needed
• Notes updated with concrete file/function references

Working Notes

• Runtime parity tweak in this pass: 5-bit selector mask added.