GXInitLightSpot

• Category: Lighting
• Matrix Status: Implemented
• Matrix Notes: Verified SDK-parity spotlight coefficient generation for all GX_SP_* modes, including invalid-cutoff fallback to GX_SP_OFF.
• Matrix Link: Gfx-GX-API-Matrix

Official SDK (Reference)

• Manual root: reference/rvlsdk/man/en_US/gx
• Primary SDK source area: demos/PikminDemo/src/gx (GC-style Dolphin GX source)
• Notes:
  • Confirm official signature/prototype
  • Confirm documented side effects (register/state updates)
  • Confirm special behavior and edge cases from manual

libPorpoise Implementation

• Runtime implementation area: src/gx
• Public API surface: include/dolphin/gx
• Notes:
  • Confirm API signature matches SDK
  • Confirm state writes match SDK semantics
  • Confirm backend behavior in PC renderer path

SDK vs Porpoise Diff

• Signature parity:
  • SDK:
  • Porpoise:
• Behavioral parity:
  • SDK:
  • Porpoise:

• Known divergence:

Validation Checklist

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

Working Notes

• Docs checked against reference/man/gfx/gx/Lighting/GXInitLightSpot.html and SDK source in reference/gx/GXLight.c.
• SDK behavior:
  • If cutoff <= 0 or cutoff > 90, force spot_func = GX_SP_OFF.
  • Computes angular attenuation coefficients (a0..a2) per selected GX_SP_* distribution formula.
  • Writes only angular coefficients in the light object.
• Runtime behavior in src/gx/pc_gx.c:
  • Mirrors cutoff validation and GX_SP_OFF fallback.
  • Uses equivalent formulas for GX_SP_FLAT/COS/COS2/SHARP/RING1/RING2/OFF.
  • Writes a0/a1/a2 only.
• Result:
  • Function semantics match SDK for spotlight attenuation setup.