Alpha Channels not really transparent - Polyloop

Tassilo · 4th December 2007, 13:38

I've set up a scene with Indirect Light (AO, no interpolation, light through transparency). To simulate print on walls, I placed planes with the print including an alpha channel onto the walls. The alpha channel is correctly set up (alpha and black have got a full value).
Rendering the scene without indirect light gives me a fine result in these planes - rendering with AO on results in a dark rectangle around my wall print (see attachment). Rendering with Full Indirect Light is fine again.
Does anybody of you know about a workaround to use these alpha channel planes without that bug with Ambient Occlusion?

Thanks a lot,
Tassilo

Piem · 4th December 2007, 13:58

Maybe they have full values..but are they compressed (jpeg or else ?).
You can multiply with a 0_1000 value.

It's also possible that you only have to disable the shininess and the highlight .

jones2000u · 5th December 2007, 02:54

It could be a kind of refraction effect. Is the graphic+alpha channel the same size area as your dark square? It is possible that you need to raise the raytracing count quite high to give enough calculations to light through the alpha and to stop it being like a piece of glass placed in front of the wall... which would cast a shadow, even though it's completely transparent.

4th December 2007, 13:38	#1 (permalink)
Tassilo Illustrator Join Date: Mar 2006 Location: Cologne, Germany Posts: 62	Alpha Channels not really transparent I've set up a scene with Indirect Light (AO, no interpolation, light through transparency). To simulate print on walls, I placed planes with the print including an alpha channel onto the walls. The alpha channel is correctly set up (alpha and black have got a full value). Rendering the scene without indirect light gives me a fine result in these planes - rendering with AO on results in a dark rectangle around my wall print (see attachment). Rendering with Full Indirect Light is fine again. Does anybody of you know about a workaround to use these alpha channel planes without that bug with Ambient Occlusion? Thanks a lot, Tassilo Attached Images

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4th December 2007, 13:58	#2 (permalink)
Piem Booh! Join Date: May 2003 Location: Rennes/fr Posts: 6,644	Maybe they have full values..but are they compressed (jpeg or else ?). You can multiply with a 0_1000 value. It's also possible that you only have to disable the shininess and the highlight .

5th December 2007, 02:54	#3 (permalink)
jones2000u NURBS Booleans are your friend Join Date: Jun 2006 Posts: 134	It could be a kind of refraction effect. Is the graphic+alpha channel the same size area as your dark square? It is possible that you need to raise the raytracing count quite high to give enough calculations to light through the alpha and to stop it being like a piece of glass placed in front of the wall... which would cast a shadow, even though it's completely transparent.