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Bumped cubemap aliasing


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#1 Mr_F_   Members   -  Reputation: 279

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Posted 20 March 2013 - 08:50 AM

I've noticed a lot of shimmering coming from shading, especially from specular and environment maps used together with normal maps, and I really really want to fix it some way.

 

The best solution I found on topic is this (because of simplicity and low performance hit): http://blog.selfshadow.com/2011/07/22/specular-showdown/

 

These Toksvig maps gave me kind of acceptable results with blinn-phong:

Without: http://oi48.tinypic.com/mlmfia.jpg

With: http://oi49.tinypic.com/346vnvd.jpg

 

However, I'm still struggling with getting them work with cubemaps. Original Toksvig paper has a little advice, saying "This effect can be modeled by computing lod for the environment map as a function of log2(some_greek_letter)", but it's not really helpful.

Anyway, we can vary the size of specular highlights, but we are still a bit limited with envmaps, because we only have a discrete number of mips and a linear interpolation between them - and I think, this limitation can break some theory behind Toksvig AA (or maybe I'm wrong).

I tried different ways to use Toksvig factor in texCUBElod, but no success, I have either aliasing or everything is just totally blurred.

 

Aliased: http://oi46.tinypic.com/2961zlv.jpg

(1-Toksvig)*numMips as lod: http://oi47.tinypic.com/344fm6v.jpg

 

And here is the best version, just brutally supersampled cubemap inside shader (11 fetches): http://oi46.tinypic.com/1679sf7.jpg

But it's a huge performance hit!

 

Is it possible to get that supersampled quality, only exploiting mips and not relying on heavy amounts of fetches?

 

Thanks in advance.



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#2 C0lumbo   Crossbones+   -  Reputation: 2133

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Posted 20 March 2013 - 11:42 AM

I remember reading a paper about that, I never tried it but it sounds like it addresses the issues you are having: http://www.nvidia.com/object/mipmapping_normal_maps.html



#3 Mr_F_   Members   -  Reputation: 279

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Posted 20 March 2013 - 01:17 PM

Well, I actually quoted this link as "original Toksvig paper" in my first post, it's clickable there )

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OK, I think then it should be log2(toksvigFactor * p), where p is kind of specular power for biggest mip level (as if it contains specular highlights). As I use Modified CubemapGen for cubemaps generation, I even know excatly this number (it's named "cosine power" there).

But results are still disappointing: http://oi50.tinypic.com/hv782f.jpg


Edited by Mr_F_, 21 March 2013 - 12:40 PM.





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