GXSetViewportJitter

• Category: Transformation and Matrix
• Matrix Status: Implemented
• Matrix Notes: SDK-parity half-line jitter rule applied (VI_FIELD_BELOW shifts top by -0.5f), with viewport/depth state handled via normal viewport path.
• 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/Transform/GXSetViewportJitter.html and SDK source in reference/gx/GXTransform.c.
• Runtime updated in src/gx/pc_gx.c:
  • Replaced parity-based jitter approximation with SDK rule:
    • if field == VI_FIELD_BELOW then top -= 0.5f
    • otherwise unchanged
  • Calls GXSetViewport(...) with the adjusted top value to keep shared viewport/depth state flow.
• Result: function-level parity now matches SDK behavior for jitter offset semantics.