I’m creating an image of a home cinema and I am experimenting with the vrayclipper object to cut away one of the walls. It works quite wekk.
However, it seems to be giving me an ‘imprint’ of some of the objects that shouldn’t be visible. The objects on which this happens are the splines with sweep modifiers on them.
Any ideas/solutions? I’d like to keep them as sweep objects rather than collapse to a mesh.
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Update: it seems not to be the sweep objects. Possibly something to do with coplanar edges on objects…am investigating.
A quick search of the forum found the suggestion to swith off Embree. This seems to work! TBH I don’t even know what embree means or does, but it makes me think we shouldn’t be using it at all?
You should generally be using it as it speeds up rendering quite a bit If you can get us a scene that we can investigate for this issue, it would be very very helpful - ideally we want Embree to work in all cases.
i know its not a direct answer to your problem (which you seem to have found) but i was in a similar situation recently, doing a cutaway, and i was determined to use vrayclipper.
however the inability to see the clip in the viewport ( it was complex, with several different depths, and the client wanted to see and adjust) and the large increase in rendertime, lead me to fall back on Scalpel, the ancient Cabas plugin. This pugin impresses me every time i use it. handles large volumes of complex geometry quickly, it rarely fails (a few small bits without end capping, out of several thousand objects) and its relatively cheap.
Yes, we have Scalpal and it is amazingly resilient. However, this current project seems to work quite nicely with the vrayclipper (as long as we don’t need embree!). The cinema room is a very simple scheme.
I think the problem in your scene is overlapping faces. What is your V-Ray version ? In 3.20 VRayClipper is modded to be more friendly with overlapping geometry.
OK, so Embree is more sensitive to coplanar faces?
The pieces of geometry are extruded volumes (created in Autocad) that are then ‘sliced’ for the different wall elements. There is therefore a duplicate face where the slicing plane is. However, this should be out of shot as the clipper cuts all of this out of view.
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 ?!
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.)
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.
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?!
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 ?
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.
If you can get us a scene that we can investigate for this issue, it would be very very helpful - ideally we want Embree to work in all cases.
