Friday, November 23, 2007

AO with MR



I really liked the results from an ambient occlusion bake with mental ray in 3DSMax, but I always got loads of errors (black splodges). Turns out that this is the low poly mesh intersecting with the high poly mesh, for some reason Mental Ray isn't able to hide the low poly mesh its baking to. So to get around this after you set up the projection cage simply go down the stack into edit poly, select all the faces and then select hide (not the hide command for objects, but the hide button in edit poly), this will hide all the faces of the model. Go back up the stack to the projection modifier and you'll see the cage again. Hit bake and you'll get a nice AO map without the black areas. Here's some settings I've found useful when doing this. The higher spread seems to bake a cavity style map rather than AO which can be very useful. (I'll post an example soon). The memory spinner will need to be increased if you have brought in a very high poly mesh from zbrush (as an .obj) and your getting an error when baking. I usually increase it to 3000MB and don't seem to get an memory errors.

4 comments:

Anthony said...

Your idea of hiding the faces in sub-object mode saved my life! I spent half a day but still did not have luck until I saw your blog, thanks man!

solarFlash said...

Glad I could help :), I scoured the internet for months before I finally found the solution.

Anonymous said...

Wow. What a lifesaver. I was ripping my hair out in huge clumps over this. Hopefully this will be fixed in the latest version of max.

Anthony Wong said...

I approached a 3dsMax display engineer and told him the problem in GDC 2008. He was not aware of that problem. Unless someone raise a voice.. else I do not think that Autodesk would improve on this:)