MR AO Bake errors

Rang3r1

Hey guys, I am getting some weird errors when I bake an AO map in 3ds max using Mental Ray. I followed this tutorial exactly, using method #2. The weird thing is that I tried it out on a less complex model to see how it worked, and it works fine. What am I doing wrong? I dont get any errors on my normal map, but for some reason the AO is really screwed up. It is an unexploded bake.

http://www.laurenscorijn.com/articles/ambient-occlusion-baking

MoP

Try setting the Object Properties of your lowpoly mesh to turn off "cast shadows" and "receive shadows". It looks like your lowpoly is occluding your highpoly here (which seems like an oddly common problem in Mental Ray in Max).

Rang3r1

Thanks MoP, but that didn't work. But I understand what you are saying, I wish I could just make mental ray ignore the low...

MoP

I've heard some people say they go into the EPoly for the lowpoly mesh, and select all faces and do Hide... I can't believe this is the only solution.

I'm pretty sure I never ran into this problem before... then again I didn't bake with Mental Ray very often.

MaD

Don't know if that method works for baking from high to low poly. I always use the third method, but you have got to exclude your low poly. There's a really good tut on UDN about it.
http://udn.epicgames.com/Three/CreatingShadeMaps.html

Rang3r1

Hey, thanks man, trying it out right now, looks like it should work. And if it still doesn't work, I am going to try the hide faces method.

katzeimsack

turn off the visibility of your cage AND lowpoly model ..
cast shadows doesn't affect ao, visibility does

Rang3r1

It worked, although it took forever with 64 samples. What I don't understand however, is that I get these errors (misses) on the AO that are absent on the normals... Since they aren't terrible I just fixed them in photoshop, instead of waiting to render another set of AO, but if someone could clue me in for next time that would be awesome.

r_fletch_r

I had a similar problem to this, a push modifier with a small value fixed it for me. makes no sense but it worked.
Your speed issue may be down to Final Gather being left on. this really slows baking down