Final Gather Question

[T-R]

Occlusion will do this for you. You can use the built in shader or download the dirtmap shader. There are a couple ways of doing this, the best bet being doing an occlusion pass and compositing it in later.

[sidiggas]

thanks....im not quite sure how to set up the ambient occlusion...all i find in Mental Ray is (mib-illum_) and stuff like that, i find nothing that says (amb_occlusion_)...when i apply the occlusion, when i find it....do i have to lower my final gather settings cause my scene becomes to bright and washed out...another thing, i dont know how to render layers seperatly...not sure what everyone is talking about when they say that

[T-R]

oh i see. It depends what version of maya you are running. If its 6.5 or 7.0 there will be an mib occlusion shader in the mental ray shader section. If you are running an older version than you need to download the dirtmap shader right here:
http://animus.brinkster.net/stuff/plg_dirtmap/plg_dirtmap.html

If you are going to composite it you need to delete all the lights in your scene and make sure raytracing is on. No FG or GI is needed. Then assign a surface shader to all your objects in the scene. From the outcolour of the surface shader plug in the dirtmap/mib occlusion and you are ready. After you render you can adjust the quality by the number of samples in the shader node. It begins at 16(i think) for testing purposes. You can also play with the min/max distance. This is important for realistic results. When you composite this pass in post you usulally use a multiply to get the final result.

If you really want to do it all in one shot(although compositing is much better for control) and you are using the dirtmap, keep all the lights and shaders on and to the diffuse slot of the shader you assign an RGB luminence node and then the dirtmap to that. The thing is if you have a ton of shaders that can be a pain in the ass. I kind of recall someone having a work around to applying this all at once.

If you are using the mib occ then you can pipe it directly into the ambient node of your shaders. I think you will need to lower the white colour in the occlusion node because the object will seem to bright.

Hope that helps.

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