from a quick glance at the scene I would guess that the mental ray materials are always double sided, there doesnt seem to be any options to change that setting but when i rebuild a material with a standard blinn using the brick texture in the diffuse and bump slots it seems to work with the correct normals.
I'm not big on using the preset materials myself so I havent really experimented with them. I'd recommend just building materials from scratch so you always have flexibility. It seems like those preset materials are intentionally simple in there interface for the arch viz artist who needs to just whack some bricks on a surface and forget about it.

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I have heard that from others, but I don't think that's the issue. The reason I say that is because it was working until I started using the materiel modifier, which actually I didn't need because the faces have ID automatically. If the materials were two sided, the described issue would have been consistent. I tried turning off the Id modifiers, but it didn't fix it.

By the way, I have been able to render with Mental Ray using the ray materials with back face cull working, so it's got to be something else. If I find anything more on this, I'll post it.

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well I'm not sure. I just set up a fresh scene, flipped the normals on a box and applied the masonary material and it renders double sided.
then I applied a standard blinn and it renders with the normals flipped, it seems like its the masonary material thats the problem and theres no settings in there to change anything except the map and the relief amount.

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Hi Tyson
I'm not sure if this helps but, I found that if I zoom really close to where I'm inside the box, then Mental Ray renders the inside walls, which is what I'm after. But if I zoom away, it renders the room as just a box.

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yeah, like I say, based on these observations it would seem that the masonary arch design material is double sided, ignoring your normals with no option to change it. your only solution here is to use a different material type like standard blinn, or set up the scene so you can place the camera inside the room.

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You know, it's funny, I was talking with a friend about this last night, he works with a guy who I guess is really good with the program. Hes friend said exactly what you said Tyson, in that they "are" two side, but he mentioned you have to turn that off in the material editor. However, he is using 2010, so maybe there was an option at that time. Maybe there is a script. My friend is going to let his friend know that he's answer didn't work, so lets see what he says.

In any case, using the defuse works just as well. I just thought it would have been nice to just drop some pre made materials onto a basic room with backface cull walls for fun and just make minor adjustments. It just doesn't make sense to me why these materials were made two sided with no option to turn that off. It kind of limits what you can do.
Putting the camera in a room works just as well. Because thankfully you can still see the inside of the room in the perspective. That's a good thing because at least you can see if whats on the walls if you needed to zoom out in the perspective.

If I hear anything more on this, I'll update this thread if possible.

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It is a strange thing, I'm not a fan of the preset materials with all the settings hidden under the hood, its much better to have flexibility. But I do see the appeal for setting up quick materials.

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