GS Primitives

The GS supports point, line, triangle, and sprite (2D rectangle with two points) primitives.

00h PRIM

  • 0-2 Primitive type
    • 0=Point
    • 1=Line
    • 2=LineStrip
    • 3=Triangle
    • 4=TriangleStrip
    • 5=TriangleFan
    • 6=Sprite
    • 7=Reserved
  • 3 Gourand shading
  • 4 Texture mapping
  • 5 Fog
  • 6 Alpha blending
  • 7 Antialiasing
  • 8 Use UV for texture coordinates (0=Use STQ)
  • 9 Use Context 2's registers for drawing (0=Use Context 1)
  • 10 Fix fragment value (related to antialiasing?)

1Ah PRMODECONT

When this register is set to 1, bits 3-10 in PRIM are used when rendering primitives. Otherwise, bits 3-10 in PRMODE are used.

1Bh PRMODE

Same as PRIM, except bits 0-2 are unused.

PRMODE can be useful when you want to draw multiple primitives with different attributes but the same type.