GXGetLightAttnK

• Category: Lighting
• Matrix Status: Implemented
• Matrix Notes: Verified distance attenuation getter reads k0/k1/k2 from light object state.
• Matrix Link: Gfx-GX-API-Matrix

Official SDK (Reference)

• Manual page: reference/man/gfx/gx/Lighting/GXGetLightAttnK.html
• Reference source: reference/gx/GXLight.c (GXGetLightAttnK)
• SDK behavior:
  • Signature: void GXGetLightAttnK(GXLightObj* lt_obj, f32* k0, f32* k1, f32* k2) (manual) / const GXLightObj* in reference source.
  • Reads distance attenuation coefficients (k[0..2]) from the provided light object.
  • Getter only; no GX/XF register writes.
  • SDK debug path validates input assumptions, then writes all three outputs.

libPorpoise Implementation

• Public API declaration: include/dolphin/gx/GXGet.h
• Runtime implementation: src/gx/pc_gx.c (GXGetLightAttnK)
• Behavior:
  • Casts light object to internal layout and returns k0/k1/k2.
  • Performs per-output null checks (k0/k1/k2) before writing.
  • Does not mutate GX renderer state.

SDK vs Porpoise Diff

• Signature parity:
  • SDK manual: GXLightObj*; SDK source uses const GXLightObj*.
  • Porpoise header: GXLightObj*; runtime uses internal void* and read-only access.
• Behavioral parity:
  • SDK: returns distance attenuation coefficients from light object storage.
  • Porpoise: same coefficient mapping (k0/k1/k2).
• Known divergence:
  • SDK-style code assumes non-null outputs; Porpoise fail-soft allows null output pointers (skips those writes).
  • SDK debug path asserts on invalid inputs; Porpoise does not assert in this getter path.

Validation Checklist

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

Working Notes

• Reference implementation writes all three outputs directly from obj->k[0..2].
• Porpoise mapping is direct and consistent with light-object layout used by init/load light paths.