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# 1 16-09-2003 , 05:10 AM
robchis's Avatar
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Join Date: Sep 2003
Posts: 9

Volume lighting and transparency

A tricky scenario here. If somebody knows a solution or a workaround, it would definitely make my week!

Scene: Night, inside a dusty old room with panes of dusty/dirty & broken glass in the window. Moonlight streaming in (ignore the moon image in the background).

I need to create the effect of rays of light from the cracks in the window lighting up the dust inside the room, AND show the two-tone lighting coming from the remaining glass and the holes in the glass .

The glass is several planes that have been sliced with the "cut faces tool", with a simple phong shader at about 50% transparency.

The rays of light are from a distant spotlight, with volume light (light fog) turned on, and using depth map shadows.

The two-tone shadows on the floor are achieved by a duplicate spotlight (in the same position), but using raytrace shadows.

The moon and the trees are actually a plane just outside the room (with casting and recieving shadows turned off), so as to block visibility of any depth of the volume light.

The problem is, the volume lighting, when it hits the glass, causes it to be intensely lit - turning white... This is what I'm trying to get rid of... I need the glass to be visible (partly transparent) and not blown out by the volume light.

I've heard there's a workaround for this situation, but I haven't found it yet. user added image

Could somebody help me?

I'll show the images to clarify things.

Attached Thumbnails

Last edited by robchis; 16-09-2003 at 05:53 AM.
# 2 16-09-2003 , 07:07 AM
kbrown's Avatar
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Enable decay regions on the light emitting the light fog and play with the settings...

EDIT: Now that I think of it again, the decay regions might not work for this situation. Rendering in layers and compositing (kind of what you've already done) might be the only answer...


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Last edited by kbrown; 16-09-2003 at 07:12 AM.
# 3 16-09-2003 , 08:42 AM
robchis's Avatar
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Originally posted by kbrown
Enable decay regions on the light emitting the light fog and play with the settings...

EDIT: Now that I think of it again, the decay regions might not work for this situation. Rendering in layers and compositing (kind of what you've already done) might be the only answer...

Thanks kbrown! But...
That would work if the stream of light was facing the normal of the panes of glass, but the light unfortunately has to be at an angle... So this would cause either overlapping of light on the glass (creating areas of white out) or having the beams of light start away from the surface of the glass enough to be noticable...

And other possibilities? Hmm... maybe render layers?

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