I've fixed the problem now using instancing which doesn't present any problems when using fog.

I've got a scene which uses Physical Sun and Sky, and when I try to connect the sky node to the mental ray volume shader in the camera to create a fog effect, everything works (including the fog),...

Can someone delete this post for me?
Thanks.

Thanks!
I think the problem was the shaders weren't assigned properly to all of the geometry, but its working now.

Whenever I try to export geometry from Maya into a .mi file, the file exported is only a few hundred bytes in size and nothing appears when I render the file in Mental Ray using render proxies.
...

I've tried most of the other formats, but when I import them, either Maya crashes or the file size ends up being really big, even after using cleanup utilities. A while ago I managed to import a...

I've got Inventor 2013 Professional fully licensed on my computer and I've had it for just over a year now.

When I try to import an Autodesk Inventor Assembly file (.iam) into Maya, Maya stops responding for about 15 minutes whilst the memory it is using increases on task manager, and then a Free Memory...

When I invert the selection from just surfaces, nothing is selected, so it is probably the number of surfaces as you said. However, the object appears to be quite simple, so is there an efficient way...

The iam is about 200KB and it references about 30MB worth of ipt's