glass and coplanar issues

[prey1979]

I have a question for you all, im trying to increase my modeling speed and one of things i find i spend alot of time on is creating the curtain wall for buildings. The time consuming part is the glass ive always tend to create my glass but make sure its offset from all the sides of the mullions by 2mm inorder to prevent co planar black blotches. What i would like to do is just create a single sheet of glass instead of doing each pane seperate... and let the mullions intersect it is this possible without getting the black blotches??

Kind Regards

Ryan

[MikeHampton]

Hmm... can you post an image of what you are talking about?

If it's what I am thinking.. you are having problems with the edge of the glass being exactly coplaner with the mullion. True, Vray doesn't handle coplainer faces very well. The coplainer faces will show up in your rendering even if you have the objects not visible to the camera.

Why don't you make one pane of glass that actually goes INTO the mullions just a little bit? Thats what I do. My modeling isn't that "cad perfect".. it slows me down too much and in the end (for what I do), if it looks right, that's all that matters.

[instinct]

What usually helps is raising the Secondary Ray Bias by a tiny amount (0.001-0.002 or alike)

Regards,
Thorsten

[gfa2]

What i would like to do is just create a single sheet of glass instead of doing each pane seperate... and let the mullions intersect it is this possible without getting the black blotches??

Kind Regards

Ryan

That's the way I've always done it, never had any problems. Like you said just make sure the mullions are pushed out a little further than the glass so that their not coplanar.

[andrewjohn81]

mike said it right. If the glass is suppose to be touching, in real life, then it is best to actually have the glass protrude right through the touching surface. This will cause the refraction to show more accurate results.

Also, with the secondary ray bias. That works sometimes, but if the surfaces are truly coplanar I haven't gotten it to work well with GI. It works well for direct lighting though. I've just got in the habit of fixing any coplanar surfaces. One bucket will render glass first, the next will render the other surface first, and some buckets will render it as a mix of both in a noise pattern or a triangular pattern. It looks kind of cool sometimes, but Definitely not what we'd want.

Check out the glass tutorial/example in the Vray help doc for a better example of what I was talking about with the glass refraction having a protruding surface. They do the same thing with the liquid inside. It's the same concept for a solid surface as well.

[prey1979]

Thanks everyone for your suggestions and time. I ended up just doing it the way i was most comfortable with for tight time frame... i however will be doing tests when i have some downtime to see what works best... thanks again for all your help!!!!

[infotech]

Sorry if this is being addressed again. I searched the forums and could not find the proper clarification.

Aside from physically adjusting faces, it was suggested that setting the Secondary Ray Bias (in the Global Switches rollout) to 0.002 could resolve noise/distortion with with coplanar faces.

This however does not work all the time. I then came across the following page in the online help docs:

http://www.spot3d.com/vray/help/150S...s_switches.htm

It mentions ... "Note that the Secondary rays bias affects only things like GI, reflections etc. In order to render the scene properly, the material assigned to the box has its 2-sided option checked."

For the life of me, I could not find this "2-sided" checkbox option anywhere in the VRay material rollouts. Can anyone confirm if this option is still available.

I did see a "Double-sided" checkbox option in the Options rollout. Unchecked this but it did not resolve the noise from coplanar surfaces.

Thanks for any clarification on this. - Ed

[infotech]

I just noticed the "2 Sided" checkbox option for 3DS Max Standard materials. Is this what the Spot3D Secondary Ray Bias example documentation meant? And does this mean this workaround is not available for VRay materials (or is not needed).

Still trying to get around noisy coplanar faces (with glass). Thanks!

[infotech]

Does anyone have any suggestions in getting around noisy coplanar faces (specifically with refractive objects) ...

... without having to physically move one of the faces away from the other?

I've tired the 0.002 Secondary Ray Bias setting in the Global Switches rollout without luck and can't find the 2-sided checkbox option anywhere in the VRay materials rollout which supposedly resolves this.

I am all ears (eyes actually) if there is a combination of checkboxes, settings and/or values that can be set to resolve this.

Its becoming a chore having to remember to move faces so that they are not coplanar.

And usually these noisy coplanar faces are discovered during renders ... which eats up a lot of time in having to modify and re-render everything again.

Appreciate any feedback on this. Thanks!

[vlado]

The double-sided option in VRayMtl does not work for refractive objects, unfortunately. However you can try the "Back face cull" option in the Global switches rollout of V-Ray.

Best regards,
Vlado

[infotech]

Thanks for the Back face cull suggestion. Unfortunately, that did not work also. I guess ... just got to prevent coplanar faces with refractive objects.