So I have to use mental ray render, and I have to use particles. Every time I create more than 1 particle cloud, or a cloud intersecting complex geometry, it messes up the shadows, and creates this boxy effect...
To recreat effect, create a particle cloud with the particle tool, duplicate it, and have them intersect. You'll get really messed up box style artifacting where they intersect.
This issue is driving me insane.. not because it's there, but because I fixed it in a scene, and forgot what I did... I just randomly clicked something, and it started rendering correctly.
The scene got deleted, and I'm trying my best not to destroy this computer.
How do I fix this? (I've been fighting maya and the internet for 5 hours straight, and it's driving me insane.)