Ambient Occlusion the "correct" method?

[Rez007]

I have a quick question I was hoping someone could help me out with, and that is how to use ambient occlusion the correct way. In the past I was told to just comp (multiply) the AO render of the image in post, but that would always result in a "dirty" feel. I have been looking around and I see some people are using the mia_material_x shader, but I cant find that shader anywhere. Is that the same as the mia_material? (without the "_x") If that is the case, how would I go about setting that up as an override/seperate pass and just using the ambient occlusion setting only for that material, without using any other material properties. Maybe what I am writing here is confusing, because I have been trying to understand various methods that I have found on forums, which may in turn be confusing me. Any help would be greatly appreciated. Thanks

[ace63]

mia_material_x is called mia_material_multioutput in SI and does not appear in the Nodes list.
You can find it under Nodes -> Illumination -> More -> Mental Images

[Rez007]

Thanks for the information. I found the node like you said and I applied it. Works great so far, but I had a couple of questions in regards to that node. Basically I could just forget about the mia_material and use the mia_material_multioutput since it is basically the same thing but just seperates the channels...is there a way to output more than just one channel during render?...is there a hidden node for that? Also, when it comes to compositing the AO layer, what would you recommend would be the best way to do it, so it takes direct light/reflections into account? Thanks a lot for your help.

[Rez007]

...Basically, I would like to know what people do to get nice and correct ambient occlusion without having it baked into the image when using the mia_material ambient occlusion with detail enhancement set to 2...or is this not possible? Thanks to anyone who has any information.

[elhemp]

Hi,

I suppose what you are asking for are two different pair of shoes. If you want to use the mia_material_x shader you should use it in conjunction with mia_x_renderchannels compound by Guillaume Laforge, which you can find here: http://frenchdog.wordpress.com/2008/10/ ... -compound/.

Second the ambient occlusion: I usually render it as a seperate pass and use it as a mask for color correction. Therefore you shouldn't get this "dirty" effect.

[Rez007]

Thanks a lot and I really appreciate the help!