mental ray’s FAIL Vol.3

loocas | 3ds Max,opinions,technical | Wednesday, April 22nd, 2009

And here we go again.

This is another of those errors I can’t seem to get rid off. It’s not as severe as in the previous example, but still annoying as hell.

mr hair bug

The problem is that mental ray renders pure black pixels or lines, completely randomly. It doesn’t write them in the alpha, though, but writes them in the beauty pass. Sure enough, with motion blur and everything, you can pretty much get rid of these bugs, but sometimes the errors are much larger than that and become extremely difficult to get rid of. Like in here:

mr hair bug 02

Another of those errors… I hate mental ray.


  1. I have finally decided that I agree with you – Mental Ray bites. I am a hobbyist / indy game dev, fairly amateur, and I’m coming across Mental Ray issues exactly like the one you describe above, especially when I attempt to bake textures to game objects. The most frustrating thing is that without a bunch of industry peers to go to for advice, chances are extremely slim that I will ever figure out what the heck is causing the rendered artifacts :(

    Comment by Takuan — April 22, 2009 @ 17:02

  2. Heya, Takuan,

    yeah, the texture baking is another dsicipline I’ve seen mental ray fail at terribly, unfortunately.

    I don’t know where the problem lies and I can’t even imagine that nobody pointed this issue out in the beta team. Especially since it’s been present in Max for so long. Thus I believe that this issue is just “some” setting somewhere in mr hidden from plain sight or pure logic that magically saves the day.

    I hope Master Zap finds his way to this blog and write how much I suck and how simple it is to avoid such problems in mental ray ;) I sure hope so, this’d save me so much trouble and frustration, not saying, time, in the end!

    Comment by loocas — April 22, 2009 @ 17:09

  3. I’m seeing this problem in mentalray for maya too. I cant find any way to get rid of it either. Please let us know if you come up with anything!

    Comment by TwoNine — May 8, 2009 @ 22:18

  4. Same problem here… It sucks…

    Comment by QUATRO — July 14, 2009 @ 11:02

  5. I have exactly the same problem with VRAY / HAIRTRIX when I enable VRAY’s motion blur .
    Maybe that problem comes directly from max ? I found that by decreasing the motion blur value, just by a bit would remove the bug, or at least decrease it.

    Comment by Jo — October 9, 2009 @ 08:55

  6. Hi all are you still having this problem with 3dsmax 2011. I started having it in max 2010 and not sure what to do??
    Thanks Sev

    Comment by Sev — September 22, 2010 @ 11:03

  7. Hi Sev, nope, it’s been solved. Check one of my follow up posts.

    Comment by loocas — September 22, 2010 @ 12:25

  8. ok…. not sure where to find your “follow up posts” here… looking to solve this problem as well in max 2011. solved it in max 2010 by using BSP2…

    Comment by skidoo — January 7, 2011 @ 21:04


    Comment by loocas — January 7, 2011 @ 21:47

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