[Sidefx-houdini-list] GLSL Function library

François Duchesneau sidefx at trinix.ca
Mon Dec 14 23:00:38 EST 2009


I've continued my test.

First problem was the way I called the texture. I've figured out I need 
a parameter of type "File - Image" and not just "File" because that 
doesn't work.
Second problem is how to generate the texture permTexture from the C 
code provided. My knowledge is too limited here but I've found on the 
web the permTexture.png that works well apart from an edge artifact.

I will put that aside for a while but eventually I'd be interested in 
using SideFx functions but I still wonder how I can call 
perlin_turbulence for example.

Thanks

François

malexander wrote:
> The files in gpgpu are heavily macro'ed to overcome a lot of hardware 
> limitations, and also so that they can run in Nvidia's Cg (Sony Cell 
> workstation) and OpenGL's GLSL. Most are texture lookups in pixel 
> coords, not UVs. You can consider code there to be like pseudocode, 
> rather than GLSL (the framework around it is also built on the fly, like 
> uniforms and other functions).
>
> All the noise functions in that directory require a source texture with 
> random values in it, otherwise it won't be terribly noisy.
> And yeah, most implementations of GLSL's noise() function that I've seen 
> return a rather un-noisy constant 0.
>
> The link Ed posted is a good quality noise method, though it still 
> requires a source texture to operate (though it specifies that texture 
> for you). You might be able to embed one in a SHOP asset, and reference 
> it from an invisible texture map parameter on the node.
>
> Cheers,
> M.
>
> François Duchesneau wrote:
>   
>> I've manage to compile it and it gives a result. However it doesn't look 
>> really like the noise.
>>
>>  From what I understand it uses a permutation texture and a lookup 
>> texture but they don't provide it. I think I can figure it out from the 
>> array of pseudo-random number in the C code. For now I'll concentrate to 
>> better understand GLSL altogether but I'm pretty confident it'll work.
>>
>> Thanks
>>
>> François
>>
>>     
>
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