shade maps or a ambient occlusion map

[joconnell]

Ambient occlusion is a term used to describe parts of a model where light gets trapped and thus they render darker such as corners of a room for example. Another type of pass which is very similar is a dirtmap pass - dirt would normally collect in the same areas as light gets trapped - again in corners of rooms or the grooves of objects or places sheltered from the elements. What happens though is that a dirtmap / ao pass looks very very similar to a skylight pass with no bounced light so a lot of people end up substituting an ao pass for global illumination to give a soft diffuse look to your lighting.

[sculpter21]

Thanks for the explanation that cleared up a great deal for me. Are you familiar with how to use it in max?

[joconnell]

Personally I don't use mental ray which has the dirtmap shader which most people use - have a look here though and it should sort you out.

http://forums.cgsociety.org/showthread.php?t=102087

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