GPU/Procedural Texture Generation

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The 3DS GPU supports procedural generation of texture data using texture unit 3. Little is known about this feature, albeit a few public hints have been dropped. The contents of this page are solely based on reports on a presentation given by DMP.

The related GPU registers can be found starting here.

Overview[edit]

Procedural texture generation has four stages:

  • Noise Module (outputs u′,v′)
  • Repeat Module (outputs u′′,v′′)
  • Base Shape (also notated as G(u′′,v′′), output g)
  • F(g) and Lookup Table

Noise Module[edit]

This stage applies noise on the input coordinates. Little is known about this other than that there are three noise parameters:

  • Amplitude
  • Frequency
  • Phase

These parameters are configured starting here.

Repeat Module[edit]

This stage performs basic texture coordinate wrapping on the noised coordinates. It supports symmetric and mirrored wrapping. They don't seem to be configurable beyond that.

Base Shape[edit]

The U’’ and V’’ coordinates are used to generate a scalar value in the range [0;1] from the wrapped coordinates using one of six functions documented here.

The output of this function is named "g".

F(g) and Lookup Table[edit]

F is a selectable function which transforms g to another scalar value. There are two known options for F:

  • the identity function
  • a triangle function

The final texel color is determined by using the value of F(g) as an index into a configurable lookup table.