Maya ambient occlusion render pass with alpha transparency?

malcolm · Oct 2010

Is there some trick to using the mib_amb_occlude node and have textures will alpha channels work?

throttlekitty · Oct 2010

Sorry, can you rephrase the question? You want to bake AO+alpha, or bake AO from a source that includes a texture alpha?

malcolm · Oct 2010

Sorry I don't want to bake the ambient occlusion I want to render it but I have some trees in my scene that use alpha channels and the ao comes out with square edges that when multiplied on top of my image look terrible. I found some guy's custom shader that let's you do this but I can't get it working it just errors out in mental ray each time I try to use it.

malcolm · Jan 2011

Finally found a shader that does ambient occlusion with alpha transparencies, still can't believe mental ray hasn't updated their fucking mib_amb_occlude shader to support this. Seriously this has to be the first and most asked question by every 3d artist as soon as they start using mental ray to render or baking ao maps. It's the p_MegaTK shader that has the magical ao, available for maya, max, xsi all versions.

http://www.puppet.tfdv.com/download/shaders_p_e.shtml

renderhjs · Jan 2011

thats interesting I was always under the impression that most AO algorithms were always geometry only based. This one must do some hit testing based on the alpha channel.

r_fletch_r · Jan 2011

I could be wrong but i was under the impression that mia_material supported this using a cutout map.

malcolm · Jan 2011

renderhjs, back in 2005 our pipeline engineer wrote a ambient occlusion baking tool that supported multiple transparencies on top of each other and I've been wishing mental ray could do this since then.

r_fletch_r, I posted on the mental ray forum and the moderator did not mention anything about the mia material. Care to test it out.

r_fletch_r · Jan 2011

they were right, this doesn't work. I was thinking of a material setup tutorial i read a while back. http://3dsmaxrendering.blogspot.com/2008/07/ambient-occlusion-with-transparency.html

apologies

Maya ambient occlusion render pass with alpha transparency?

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