Basically I have a character that is clothed, cloth simmed with syflex, has multi layered clothing (pants, t-shirt and sweat shirt), and has a pretty standard 3 point light set up using dmap shadows for the lights. I prefer using dmaps for an obvious number of reasons, so giving an answer of "just raytrace your shadows" isn't something I'm interested in (mainly because I can use ray traced shadows but to get soft shadows on ray traced shadows is extremely expensive compared to using dmaps). Basically what's happening is there is a shadow showing up midway on the t-shirt right where the pants end around the waist line. If I turn off "casts shadows" on the shirt then it goes away, but then I loose the shadows being cast by the shirt, which of course I need. I'm not really concerned with shadows being cast by the whole character to the ground, this is more of self shadowing on the clothing etc. If I turn dmap shadows off and use ray traced shadows it works fine, if I render in the software renderer with dmap shadows it works fine. Only when I use dmap shadows in mental ray does this problem surface. I basically narrowed the problem down to the softness attribute of the dmap shadow. No amount of increasing the dmap resolution or samples fixed the problem. If I set the softness attribute to 0 then the problem goes away, as soon as I turn it up to .001 it comes back. I was thinking there might be an issue with the proximity of the geometry of the t-shirt and pants, but that's not really the case because the sweatshirt and t-shirt are right on top of each other and don't have this issue. I've checked the normals on both the t-shirts and pants, they are pointing where they should be.
So if anyone has run into a similar problem let me know. I'd really like to find a solution to this because it's going to be an extreme time saver when it comes to rendering. Thanks.