VrayClipper seems to have issues with sweep objects

[matanov]

Hello,

We have tried using Vray Clipper. Guess everybody is aware that depending on system units - cm, m, inches, the accuracy varies a lot. We had a scene modeled in cm, with coplanar faces of different objects, lying at same plane , on "theory".
Embree option being turned off worked partially - we still got some strange artifacts. Then we put the same objects in a scene with system units set to meters - no objects/ faces change at all, again with embree option turned off - artifacts were gone.
3ds max Design 2014 here! Constantly get accuracy issues! Guess this leads to problems with clipper. Maybe clipper needs to have sort of threshold, depending on scene units ?!

V-Ray version ? Can you send me a scene that reproduces the issue with the different scene units ? (peter.matanov@chaosgroup.com)

[Deflaminis]

I had a scene a while back that had a problem like this, but I discovered I only had to turn off the embree motion blur to fix it. (It was the only option at that point I think, there was no hair option.)

[KOLIBA]

It will take time to find the scene - it is in the archives somewhere. We have not had any other projects recently that forced us to use the clipper.
As far as remember - Vray version was 3.0.X - not sure the final number, we keep updating to very last version.

https://www.dropbox.com/sh/1h9svyvl9...BCews0t2a?dl=0

Really quick test - different scene units- mm, cm, inches and meters, same objects - 2 boxes of same size, three scenarios - faces of two boxes and clipper - coplanar, clipper and face of one box -coplanar, and third scenario - clipper and faces not coplanar. ( no Xform applied) !
Of what we see from this fairly simple scene - looks like we have just had the luck to be in scenario with no artifacts!
Looks like 3ds max issue to us!?
Maybe sort of a width added to clipper might be a solution?!

[yavor.rubenov]

Hello,

Having coplanar faces is a general problem for renderers - here is a render with the default scanline render from one of the scenes (clipper-cm.max - deleted the clipper, set standard materials)



At every shading point the renderer randomly picks one of the coplanar faces and shades it - you get the visible artifacts.

Adding a clipper just makes the situation even worse. To determine the shading we must work with the geometry faces and when they overlap it is not possible to consistently do the same thing at every shade point.

For V-Ray 3.1 we entirely changed parts of the clipper algorithm so that it handles overlapping faces more consistently but it is still a problem in some cases.

Maybe sort of a width added to clipper might be a solution?!

We are considering adding an option in the clipper to work with arbitrary meshes - that way you can better define what parts of the geometry are to be clipped. But then again - even with meshes or with width added to the clipper - coplanar faces will probably cause issues in some cases. If for example the clip mesh has coplanar face with some of the geometry - how should we treat that face - is it inside or outside ?

Best regards,
Yavor

[tricky]

Hello,

Having coplanar faces is a general problem for renderers - here is a render with the default scanline render from one of the scenes (clipper-cm.max - deleted the clipper, set standard materials)

[ATTACH=CONFIG]24956[/ATTACH]

At every shading point the renderer randomly picks one of the coplanar faces and shades it - you get the visible artifacts.

The coplanar problem you highlight here is, of course, an issue for a renderer, but it is very different to the coplanar issue I am talking about which I represent with this graphic:-



Here, the coplanar faces are out of site as they just share a common border. Its only from the days of rendering with Lightscape where we tried to delete all these sorts of 'hidden' faces.

[yavor.rubenov]

The coplanar faces that are out of sight should work correctly with V-Ray 3.1 and 3.2

Best regards,
Yavor

[thomes]

thanks for the hit with disabling embree. that saved my life (vray 3-60-04)

[yavor.rubenov]

Hello,

It would be helpful if you could send us the scene for some investigation. We would like to make it work with embree enabled too.

Best regards,
Yavor

[thomes]

here we go...
reduced to the min

BTW... there is another error in 3.60.04 with physical cam and perspective control. you dont get what you see! ...with lens shift vertical and auto vertical tilt checked. you can also check it out in this file. dont know if its your thing or autodesks