clouds textures

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

This is a quick way:

void colorpict dist
echo 11 noop noop noop image.pic fisheye.cal fish_u fish_v -rx 90 -rz 90
0
0

dist glow skyglow
0
0
4 1 1 1 0

skyglow source sky
0
0
4 0 0 1 180

Hope it works/helps :slight_smile:
Ciao
G.

SP you need a -vth image...

···

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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

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 <[email protected]>
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

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

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 <[email protected]>
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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