Dark streaks / patches on figure?

jim_doria

I am seeing these weird dark patches on my character that have appeared as I've been messing around with mesh lights. There are a couple of large lights on the ceiling, and three mesh lights specifically for the character - an overhead, a front fill and a bottom fill. There are some point lights in the room as well.

They aren't shadows - the mesh light is directly over the character and slightly to the front. The only thing conceivably in a position to cast shadows would be the hair, and if I hide it they still appear.

It's not the "too far from the origin" problem. It's not the "texture seams / uv maps" problem. It's not even (I don't think) the "Iray terminator artifact" problem.

The one down the center of the arm is the most prominent, but they appear at various points on the character's upper body.

Any idea what might be causing these? Is it just Iray messing up because I've got too many light sources?

jim_doria

OK, I solved this one. For anyone who's interested...

By "messing around with mesh lights" I partly meant using a trick I had found (I think from a Sickleyield tutorial?) of setting the cutout opacity of the mesh light to a small value (the tut recommended .001, I tried it at .0001) so that you could have the light in the frame and casting illumination, but not see the light itself. 

Turns out that's what was causing this. Apparently, the light from these mostly transparent lights was creating dark spots where the opaque light would have created highlights. I set the light's Cutout Opacity to 1 and the dark spots went away (well, turned into bright spots.)

Too bad. I really liked this trick.