mental ray’s FAIL Vol.2

loocas | 3ds Max,opinions,software,technical | Monday, April 13th, 2009

As a follow up to my previous rant about mental ray in 3ds Max, here’s another beautiful example of its “usefullnes” in production.

I’ve been working on some “fur” shots on the latest project I’m about to finish in about two weeks from now and I haven’t berated so much in a long time! Here’s a test shot of a furry ball very roughly put together just to demonstrate the point:

mrPrim beauty

and here is the problem seen on the very same render’s alpha channel:

mrPrim alpha

this is what happens when you superimpose the render over an arbitrary background:

mrPrim comp

Isn’t it wonderful?!

I remember this bug from the old 3ds Max 8 days. Unfortunately, it’s the year 2009 and this was rendered in 3ds Max 2009 (will test 3ds Max 2010 asap) with mrPrim set as the Hair Rendering method. Now this can be avoided by using a different Ray Sampler the Fast Rasterizer, however, this option yields even less predictable and reliable results. Although the hair alpha channel gets rendered correcty, I often get artifacts in the render buffers in forms of random black pixels or random black lines (not affecting the alpha though), but some times the rendering simply gets stuck forever never actually finishing the current frame, which is very bad!

So, please, those of you who use mental ray daily, educate me, I can’t believe this would just slip out in this form as a “final and ready for production” product! I refuse to believe so!


  1. It’s a 3dsmax bug, with mental ray in Softimage XSI all is working ok.

    Comment by César Sáez — April 13, 2009 @ 23:33

  2. Heya Cesar,

    yeah, I know it’s a 3ds Max thing. In fact, it has to be either the tranlsator or something is seriously fucked up in the API or the “tie-up” part of mental ray.

    However, some friends of mine, also on XSI, told me they too have had issues with random black pixels or lines in the render buffer.

    Comment by loocas — April 13, 2009 @ 23:38

  3. Hi,

    Yes you’re right, my “with mental ray in Softimage XSI all is working ok” don’t mean absolutly ALL… mental ray is picky…

    Comment by César Sáez — April 14, 2009 @ 00:54

  4. Yeah, it’s “picky” allright, but I’d be cool with that in 3ds Max, because in Max, rather than “picky”, I’d call it “broken” :(

    Comment by loocas — April 14, 2009 @ 01:00

  5. if you still want the answerand if you use rasterizer as your primary renderer: in “quality” there is “rasterizer”, below that there is “rasterizer transparency” put a 0 on that:D this solution worked for me in maya btw; you need to change the idea for max i dont know its language:D..

    Comment by beli — August 28, 2009 @ 15:06

  6. Hi beli, thanks for the tip, I appretiate it. I’ll try it when I get the chance.

    Comment by loocas — August 28, 2009 @ 15:25

  7. Mental ray in 3DS Max fail entirely.

    Comment by Maxwell — September 3, 2009 @ 13:34

  8. I have been having these same problems in Maya 2011 with Shave and a Haircut.
    Thank you beli, your suggestion to set “rasterizer transparency ” to = 0 worked *(but only if Features: Primary Renderer = Rasterizer (rapid motion)).

    Comment by PixelPincher — January 3, 2011 @ 16:20

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