[Radiance-general] clouds textures

[bob coyne]

Thanks a lot (and to Guilio too).  This is a great help!

Greg Ward wrote:

> Hi Bob,
>
> You need to use a mapping that indexes off the ray directions rather  
> than locations, which are meaningless for sources (as you  
> discovered).  The fisheye.cal file included in the ray/lib directory  
> should be a good starting point:
>
> {
>         Calculate coordinates for a 180 degree fisheye lens.
>         Assume view direction is (0,1,0), view up (0,0,1), (1,0,0)  
> right.
>
>         4/30/90
> }
>
> fish_u = .5 + Dx/fish_Rxz * fish_Ry;
> fish_v = .5 + Dz/fish_Rxz * fish_Ry;
>
> fish_Rxz = sqrt(Dx*Dx + Dz*Dz);
> fish_Ry = Acos(Dy) / PI;
>
> ----------
> You may need to apply a rotation to this if your z-axis points up, as  
> is usually the case.  Something like:
>
> void colorpict cloud_pat
> 9 red green blue clouds.pic fisheye.cal fish_u fish_v -rx 90
> 0
> 0
>
> cloud_pat brightfunc skyfunc
> 2 skybr skybright.cal
> 0
> 7 1 3.58e+01 3.07e+01 1.55e+00 0.054270 -0.269929 0.961350
>
> -------
> In this example, I have added your cloud pattern to a sky created by  
> gensky.  If you have an HDR image of the sky you're working from, you  
> may just be able to go with that.
>
> Additional resources:
>
> Mark Stock's Radiance Miscellany page:
>     http://mark.technolope.org/pages/radmisc.html
>
> Link to Simon Crone's Radiance skies collection:
>     http://radsite.lbl.gov/radiance/pub/libraries/
>
> -Greg
>
>> From: bob coyne <coyne at semanticlight.com>
>> Date: January 31, 2006 9:48:36 AM PST
>>
>> What's the best way to get a sky with a cloud texture map in  
>> Radiance (assuming
>> the cloud texture map is already "sphericized")?  I've tried  
>> applying a COLORPICT pattern onto
>> the sky SOURCE  but it doesn't work (I get black).  I assume this  is 
>> because the UV
>> coordinates aren't available in the same way (with Lu, Lv) that  
>> works with mesh objects.
>>
>> I've also tried making a polygonal mesh sky dome. That's easily  
>> textured but creates other problems
>> (shadows and other lighting effects on the sky) .
>>
>> Thanks for any help or guidance on how to do this sort of thing!
>>
>> - Bob
>>
>
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