GPU/Procedural Texture Generation: Difference between revisions

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The 3DS GPU supports procedural generation of texture data using [[GPU_Textures|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 [http://www.4gamer.net/games/017/G001762/20120822007/ presentation] given by DMP.
[[Category:GPU]]
The 3DS GPU supports procedural generation of texture data using [[GPU/Internal_Registers#GPUREG_TEXUNIT3_PROCTEX0|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 [http://www.4gamer.net/games/017/G001762/20120822007/ presentation] given by DMP.
 
The related GPU registers can be found starting [[GPU/Internal_Registers#GPUREG_TEXUNIT3_PROCTEX0|here]].


== Overview ==
== Overview ==
Procedural texture generation has four stages:
Procedural texture generation has four stages:
* Noise Module
* Noise Module (outputs u′,v′)
* Repeat Module
* Repeat Module (outputs u′′,v′′)
* Base Shape
* Base Shape (also notated as G(u′′,v′′), output g)
* F(g) and Lookup Table
* F(g) and Lookup Table


== Noise Module ==
== Noise Module ==
This stage applies noise on the input coordinates. Little is known about this other than that there are three noise parameters:
This stage applies noise on the input coordinates. Little is known about this other than that there are three noise parameters:
* Turbulence (?)
* Amplitude
* Frequency
* Frequency
* Phase
* Phase
These parameters are configured starting [[GPU/Internal_Registers#GPUREG_TEXUNIT3_PROCTEX1|here]].


== Repeat Module ==
== Repeat Module ==
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== Base Shape ==
== Base Shape ==


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:
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 [[GPU/Internal_Registers#GPUREG_TEXUNIT3_PROCTEX0|here]].
* ADDSQRT2: sqrt(U’’*U’’+V’’*V’’) (?)
* U’’: U’’ (discards V’’)
* V’’: V’’ (discards U’’)
* MIN: min(U’’,V’’)
* MAX: min(U’’,V’’)
* ADD: U’’+V’’


The output of this function is named "g".
The output of this function is named "g".
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* a triangle 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.
The final texel color is determined by using the value of F(g) as an index into a configurable [[GPU/Internal_Registers#GPUREG_PROCTEX_LUT|lookup table]].