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View Full Version : Ambiant Occlusion and normal Map !


SebKaine
05-28-2007, 02:29 PM
Hi !

I'm trying to achieve ambiant occlusion , with normal map. i'm using maya 7 and Mental ray . The normal map was created in ZB2. The normal map works perfectly on a blinn, but when i try to connect my normal map to the occlusion surface shader there is no NormalCamera attribute. I try with the Mi.NormalCamera but with no succes! Does anybody know a custom surface shader that allow to create ambiant occlusion with normal mapping on MR.

Thanks For your Help ! :)

hakanpersson
05-28-2007, 10:31 PM
If it helps you, you can connect your ambient occ to the diffuse channel of a blinn.

SebKaine
05-29-2007, 12:10 AM
Thanks for your answer Hakan ! in facts it looks to be an excellent idea ! But i've try to connect my amb_occlu node to the diffuse with the help of a RGB_Lumi node without succes ! Maybe there is a little trick ...

Could you please show me your node graph for doing this ! I find an other option that give pretty good result ! i connect a cavity Map in the diffuse , it's not occlusion but it give nearly the same effects .

But i'm curious to learn your trick !

Cheers

SK

arjan_meerten
05-29-2007, 12:30 AM
You can try rendering out a bump in zbrush and use that on the diffuse or color in combination with ambient occlusion in maya.
It is faster and exactly the same as an ambient occlusion on the normal map.

SebKaine
05-29-2007, 07:44 PM
Hi Arjan ! Thanks for your help ! Again it sounds to be smart ! but The only map that i know at this time are Displace, Normal and Cavity . How do you create Bump map With Zbrush ? You take your disp map and add some contrast on it ? or zb can directly outpout it for you ?

i'm also interested if you know other type of map that ZB can outpout for compositing tweaking !

Thanks for your support !

Cheers

SK

hakanpersson
05-29-2007, 10:25 PM
exactly the same as an ambient occlusion on the normal map.
Huh?

SebKaine: I actually misunderstood your first request, I thought you had an ambocc in textureformat. diffuse node is for texturebased amb-occlusionmaps (cavity maps from zb is a sort of amb occ map).
You can connect "mib_amb_occ"-node to the diffuse channel if I remember correctly, that way you will get ambocc on render, if you want to render that only (aka, those white and black renders we everywhere), you should be able to connect it to your default color as any texture. But im not sure how the normalmap would react that way.

/Håkan

hakanpersson
05-29-2007, 10:29 PM
btw...
How do you create Bump map With Zbrush ? You take your disp map and add some contrast on it ? or zb can directly outpout it for you ?

In this matter the displacement is pretty much/exact the same as a bumpmap. But you might want to generate the displacement from a higher level, so that it only captures highres details.

SebKaine
05-30-2007, 12:30 AM
Ok Hakan thanks , i had to find the trick to connect mib_amb_occ to the diffuse channel , you can't do this by default , but i remember this manip from a tutorial , but i'm unable to find it now ... maybe on mymentalray

arjan_meerten
05-30-2007, 01:10 PM
You can connect the ambient occlusion and the displacement map to a multiply node or a layered texture and connect it to a luminace node. connect the luminace node to the diffuse channel. and connect the normal map to the bump.
But if there is a way to include a normal map in the occlusion calculation that would be interesting.

bgawboy
05-30-2007, 05:11 PM
The key is to have the bump map change the normal before doing the AO.

mi standard shaders and maya standard shaders expect a normal to be passed in different ways. In order to convert from a maya bump into mi convention, use the misss_set_normal node. The input is the maya bump node, and the output would go into slot in an mi shader designed for calling out the bump first, such as in fast_sss, or called first in some kind of shader list, or sequentially ordered shader execution.

A Phenomenon can be made which executes the shader list.

http://forum.lamrug.org/viewtopic.php?t=1099

So one could design a simple Phenomenon that wrapped a bump around ao using misss_set_normal followed by mib_amb_occlusion.

SebKaine
06-04-2007, 10:12 AM
Thanks a lot For your answers guys ! i got it :thumbsup:

Cheers

SK

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