black surfaces (vray bug?)

[zsero]

Have a look at the attached image. It is a scene imported from Archicad via a 3ds file. I used GI with simple environment lighting color with no default lights.

Override material is ON, with a standard vray material.

I have the same result with material attached to all objects.

The material has 2 sided checked, as originally.

 

Any ide how to solve this?

[Tyorl]

Check normals, and coplanar faces.

[ShaunDon]

Like Alex said, you've either got screwed up normals or a duplicate face. The best thing to do is correct the problem with the geometry, but if you run into a job where that's too much work you can adjust the secondary ray bias under global switches from 0.0 up to .001 or .002 -- however it's possible that this can cause other problems down the road, so if you can fix the model -- FIX THE MODEL!

 

Good luck!

Shaun

[zsero]

Like Alex said, you've either got screwed up normals or a duplicate face. The best thing to do is correct the problem with the geometry, but if you run into a job where that's too much work you can adjust the secondary ray bias under global switches from 0.0 up to .001 or .002 -- however it's possible that this can cause other problems down the road, so if you can fix the model -- FIX THE MODEL!

 

Good luck!

Shaun

 

Thanks, for the solution!

This plane had two polygons, one on each side. Deleting one of them made it work!

[skippy]

sometime i get black areas if some object overlap another.... check maybe u have some another object inside it etc...

[zsero]

sometime i get black areas if some object overlap another.... check maybe u have some another object inside it etc...

 

Yes, that was the problem, actually two planes on each other (in the same mesh, but that does not matter.)

 

Is there any possible automatization method for discovering and deleting faces like that? Maybe a maxscript guru could do it.

[ShaunDon]

I usually throw an STL check modifier on my troublesome meshes. That will at least let you know if you have double faces -- though I don't think it understands ones that merely overlap. Those you'll have to resolve on your own.

 

Shaun

[zsero]

And is it possible to use any other file transfer method to export from Archicad? I think it is ArchiCAD which is buggy, max's side is correct.

[zsero]

if you run into a job where that's too much work you can adjust the secondary ray bias under global switches from 0.0 up to .001 or .002

 

After messing with fixing meshes and trying all the export file formats from ArchiCAD I went that way! (EDIT: actually it is not possible to type 0.001 by keyboard - it is only possible by clicking on the arrows).

 

Idea: I've heard, that C4D has a very good native ArchiCAD importer! What about importing into C4D and then converting the file to max? Has anyone tried it?

 

Thanks for the quick solution!

[ShaunDon]

http://www.chaosgroup.com/forum/phpBB2/viewtopic.php?t=13761

 

Curious, I was referencing this thread on the VRay board -- and they specifically say .001-.002, NOT .01-.02. But if it works, it works!

 

Shaun

[Tim Saunders]

sadly 150% of problems in vray where people have objects rendering black is due to coplanar faces. it seams so easy for us who model in viz/max in the first place, but to those who import models from other programs, make that the first thing you check. becasue i almost dare to say coplanar faces is always the culpret.

[zsero]

And do you know any automatic solution that deletes one of the coplanar faces? After half an hour of fixing an imported modell, I found out that all faces had the same problem (coplanar faces as you called it) and the fixing was a mechanical - thus very boring - work.

 

I think it really needs a maxscript solution - I wish could do it.

[Tim Saunders]

thats that sad thing. and the first reason i stopped modeling in ADT. ADT has the same problem, peobably even worse.

[Christopher Nichols]

Co-plannar faces and flipped normals is just bad modeling (and model tranlations). Rendering engines that are "forgiving" of these flaws make matters worse, because the promotes sloppy modeling. Most of these issues come from model translation. FormZ is really bad about his. Just be happy that you are limited to that. In Renderman, people have to worry about all their polies being in quads rather than tris.