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AO Mental Ray 3ds max Problem! Please Help!

interpolator
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BradMyers82 interpolator
Okay, this is the second time I have run into this problem and I have no clue what could be causing it. The only work around I have found is to not use mental ray all together.

I read another post a while ago where EricChadwick and Vig were talking and thought the solution was there but I guess I was wrong because it didn't work.

To elaborate, I am using the mental ray renderer inside of 3ds max2009 64 bit to bake Ambient Occlusion.

Since I have no choice but to use mental ray for AO (lightmap with defaut scanline renderer doesn't turn out as good in my opinion) I am also baking my normals, and simple diffuse.

The problem is that for no apparent reason, the mental ray renderer won't render entire chunks of my uv's. It acts as if they are not even there at all.

Furthermore, if I bake with the default scanline renderer I have no issues at all. The only problem really is that I can't add the Mr ambient occlusion unless I am using the mental ray renderer.

So back to what EricChadwick and Vig were saying. I tried to go to my editable poly (on my low poly mesh) and select and hide all faces, because they said there is a bug with mental ray where it renders the low poly or something. This didn't work.

Other points to make:
I have tried using other versions of max when I had the problem last time including max9, 2008, and 2009. Same exact problem with these apps.
I have check to make sure there are no overlapping faces, and there aren't
I have tried using different map channels with slightly different uvw setups, and it didn't work.
I have tried detaching the parts I am having trouble with and baking, and it literally bakes nothing
I now am using a different computer than the last time I ran into this problem (I got a new motherboard) but the graphic card is the same. Not sure if it could even possibly be do to something like my graphic card. Btw, I am using direct 3d with an nvidia geforce 8800gt video card.
I have tried converting to editable mesh and placing xform on the stack and this did nothing

Is there a setting or something specific to mental ray that I should have checked? Its the only thing I can think of right now.

So if anyone has any idea what this might be all about please help! I would really owe you big time.

texture output examples:
MentalRay_Bug.jpg

Replies

  • FicWill
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    FicWill polycounter lvl 17
    Are those uv islands upside-down?
  • BradMyers82
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    BradMyers82 interpolator
    Yeah, I think so. Good point! Could that mean something. I mean the hands for example are facing every which way and those islands render out fine.
  • BradMyers82
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    BradMyers82 interpolator
    I'll flip them around for the hell of it and see what happens.

    [Edit] maybe inverted too, I'll play around with that. Really good idea FicWill.
  • Mark Dygert
    Yep, any time you mirror geometry (use symmetry instead it doesn't screw up the UVs) or use Flip in the UV Editor window (use rotate as best you can) it turns the UV pieces inside out. MR looks at the back of the poly, sees through it and renders nothing.

    The quick way to fix it is to go into the UV Editor window > Face Mode > Select > Select Inverted Faces and flip whatever it highlights.

    The easier long term solution is to check and make sure your UV's are right facing as you go, knowing what causes that helps correct it as it happens =)


    OR


    You have overlapping UV pieces. This is less likely as it normally makes a jumbled mess.
  • BradMyers82
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    BradMyers82 interpolator
    Wow vig, asking a technical question on polycount is like putting up the Bat signal for you, ha ha!

    BTW, inverting the faces did the trick.

    Thank you guys sooooo much for helping me out here, this really had me stumped. As you can see from the post I nearly tried everything at this point, I just didn't think the solution could be so simple.

    You guys rock!
  • Mark Dygert
    Hopefully Batman (EricChadwick) won't get to busy with his awesome new job.
    Because Nightwing doesn't patrol Gotham that much heh...
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