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Random artifacts on surfaces (Mental Ray)
show user profile  Larz2
Hello !
When rendering (HD) an rather complex animation I get random artifacts on many surfaces (Mental Ray renderer, 1 x mr Area Spot, 4 x Omni lights).

There is no surface errors when I render a selected object, or a small group of objects, but when the whole scene is rendered, these 'holes' appear on certain (flat?) surfaces. Objects have thicknes.
Artifacts change shape and position for every frame.

See problem here:
(some of the errors marked green)
(no surface errors when render a small Group of objects)

Can you please help me and tell me how to solve this strange and very annoying problem?

(3DS Max v2012 x64)


read 474 times
7/21/2015 6:03:07 PM (last edit: 7/21/2015 6:08:29 PM)
show user profile  Nik Clark
It looks like a scale issue to me.

read 468 times
7/21/2015 6:10:48 PM (last edit: 7/21/2015 6:10:48 PM)
show user profile  Larz2
Thanks for your swift reply, Nik.

Can you please explain how to solve this "scale issue"?


read 464 times
7/21/2015 6:33:17 PM (last edit: 7/21/2015 6:33:17 PM)
show user profile  roccodiablo
it looks like coplanar surfaces to me but judging by the complexity of your model I'd say you know what you're doing so it most likely isn't that!

It would make sense why they don't appear when you just render out parts as well as possibly the overlapping surfaces have been removed?

Other than that, I have no idea..
read 460 times
7/21/2015 7:08:06 PM (last edit: 7/21/2015 7:08:06 PM)
show user profile  Larz2
Thanks for your suggestion, roccodiablo.
But when I tried to move the object away from the other objects, the error still persist!
(green color part moved away from other objects)

Other suggestions, please?

read 449 times
7/21/2015 8:26:36 PM (last edit: 7/21/2015 8:42:42 PM)
show user profile  Nik Clark
Are they imported from another package? Sometimes you get really messed up faces.

The scale thing: Max sucks with really small and large scale. You might try scaling up or down (a lot) the model to see if you are having scale problems.

read 438 times
7/21/2015 8:56:37 PM (last edit: 7/21/2015 8:56:37 PM)
show user profile  LionDebt
Most likely it's dodgy topology.

Post an edged-face screen shot so we can see the edge loops.

edit: Oh, it's only when you render it out? Odd.

But in your second image posted (on your first post) those two black/gradient areas on the blue mesh scream out "horrible topology". Show us your topo and we can probably help you better.
read 429 times
7/21/2015 10:41:33 PM (last edit: 7/21/2015 10:41:33 PM)
show user profile  Larz2
Problem solved!!!
Thanks Nik, the error seems to come from the imported Rhino model.

When I redraw the problem-parts, it render perfect! Fortunately, not all parts need to be redrawn!

Also thanks to LionDebt - bad topology in some parts was the problem. Thanks!

What I don't understand, is why the problem only arise when many (all?) parts is rendered?

Thank you all for your help, now I can move on!

Best regards,
read 424 times
7/21/2015 11:33:35 PM (last edit: 7/21/2015 11:34:15 PM)
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