Ambient Occlusion for transparent objects!!


Hi everyone!

Is it normal to render AO even for transparent objects (even if they are 1% or 100%, reflective, refractive etc etc)???

In a company I worked for they were used to make the AO pass hiding all the transparent objects…I’d like to know if it’s the right way or not…




Hi AJDonald,

It really depends on two factors.

  1. If you are baking your occlusion maps. In this case you can hide your transparent objects, unless you want occlusion from the objects. In this case you may want to check out this link

  2. If you’re using render passes and using refraction. If an object is refracting, anything behind it there will be distortion. If you hide this object the distortion will no longer exist and your render pass will not be aligned with the others. For this I would recommend leaving the transparent shader on your object at render time and then using this for your pass.


Technically you wouldnt want occlusion on glass objects as such - but it all depends how you use it. In some cases a label pass and be used to clean up any unwanted occlusion, but may affect any occlusion in the background. You would only want to hide the primary visibility as the object itself could generate occlusion to a surface its contacting. Most people like to multiply their occ however using it in other ways can result in less effect on less visable surfaces - which can work well.

End of the day it is an approximated process and if you are going to render using such a method, a case by case situation is the best approach. Its the trade off for faster results.


Hi guys and thanks for the replies!

I have another question…I want to make a AO pass…I know how to do that…but I want to see the bumped materials in the AO pass…is it possible???

Thanks again :slight_smile:


Yes there is…

Use the mia Material x shader… make it white. turn on AO and setup your AO colour… then add a bump. This should result in a bump mapped AO.


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