So… if I understand correctly, Ambient Occlusion is not yet in the beta versions of VRay available to us, right?
If so, how do people recomend doing a dirt map that works this way?
it is essentially a map of how much envieronment each point see’s.. so if you really wanted to fake it, you could simply RendertoTexture a mid grey object in a white background/skylight
not as easy as a dirtymap, but thats basically what it does 
You can also composite them with mentalray occlusion shader.
What happened to good old fashion texture mapping? Dirt looks more real when it is painted. Just MHO…
The specific look I am going for is more like what Ambient Occlusion does. It is a quick way to add to the look of some old, rusted metal. Plus, I am short on time and painting the texture will take too long.
Not to mention, I try to use all procedural maps.
yeah why not use mental ray’s ao shader?
Might help?!?!
Vray ambient occlusion script
http://www.chaosgroup.com/forum/phpBB2/viewtopic.php?t=9399&highlight=ambient+occlusion+script
well he asked for a dirtmap, which can be used in interiors. that script, while cool, is far from a dirtmap.
The only way for interiors is to do it with mental rays version of AO and comp it in later, its not too slow either, just remember to remove the glass.