Mental Ray rendering cards + transparency

ceebee

I'm working on a character and I want to use cards instead of trying to do the whole hair system in curves so I did a quick test to see if I'll run into any issues. I almost got it perfect but the damn border of the card was showing up in my shadows. If I dont fix this before I paint alpha for all my cards I'm screwed.

Any ideas how to fix it? I'm using Maya 2011 with raytrace shadows.

Firebert

in the shader attributes
raytrace tab
turn shadow attenuation to 0

GabeLamas

I couldn't help but notice this thread as I was looking into transparency with cards. Like ceebee I am in a similar pickle. Lately I’ve been having trouble with two projects dealing with Human hair and grass planes. Now Firebert your advice on turning shadow attenuation to 0 helped me a little, but I’ve yet to accomplish my goal in Maya. I’ve been trying to figure out a way to render cards with textures w/alpha maps without having the ENTIRE card cast it’s shadow. Instead of the grass texture on my cards casting the shadow I get the mesh itself casting the shadow, making it look like the leaves are wider than they should be. It seems out of place. I’m also looking into the post-compositing so it doesn’t stop there. In different render passes such as “DirectIrradianceNoShadow” and “DiffuseMaterialColor” I get the entirety of the card instead of the alpha parts being invisible and transparent. I’ve tried posting about this on another thread but to no avail:

http://www.polycount.com/forum/showthread.php?t=153062

I’ve attached some test renders for clarity. Just so you know, the grass texture and the platform share the same texture map, but I doubt that will be a problem. In the same shader I’m now at the point where I’ve made the COLOR, NORMAL, SPECULAR, and SPECULAR COLOR Maps a 32-Bit .TGA file with an alpha channel. The Alpha maps are transparent in the Master Beauty render, but again they will show up in other types of passes as stated before. And as you can see there is some overlapping in each of these meshes, and that's why I'm posting.

And just like ceebee, some advice on the matter would really help.