NV2A/Vertex Shader

The Xbox implements https://www.opengl.org/registry/specs/NV/vertex_program.txt and https://www.opengl.org/registry/specs/NV/vertex_program1_1.txt This article will mainly focus on actual encoding on hardware as the behaviour is mostly outlined in those GL extensions already.

Registers

• 16 input registers v[0] to v[15] (from vertex, v[0] is fed from LAUNCH_DATA for VSPs)
• output registers: o[0] to o[?] (initialized to XYZ=0x00000000 W=0x3F800000)

 * Following indices are aliased: Pos, oD0, oD1, oFog, oPts, oB0, oB1, oT0, oT1, oT2, oT3

• 1 Address register: A0.x
• 12 temporary registers: R0 to R11 (initialized to XYZW=0x00000000)

 * The POS register is mirrored as R12 so it can be used as source operand, so effectively you have 13 temporaries

Instructions

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