Strange glitch

[George Ioannidis]

Hi Roy,

Working on office interior I made some pictures for the wall. There was strange behavior when glass and gray painting frame faces touch each other. See attached. I solved the problem leaving small gap between them (1mm). Is it known restriction?

Regards.

[Roy Hirshkowitz]

Coincident faces are always a problem-- not just for us but for other renderers as well.  Avoid them if possible.

[George Ioannidis]

Thank you Roy. Finally I did pictures all with space gap.

 

Back to your advice: Does it mean that it is better to have all the furniture slightly "floating" above the floor in e.g. 1mm height? Will this "trick" improve anything as regards to rendering time for instance?

[Roy Hirshkowitz]

No-- don't float the furniture.  It only matters when both surfaces are visible.  If you think about it, there's no reliable way to tell which surface a ray has hit if they're both occupying the same physical space.  The results in nXt's case will not be consistent-- sometimes it will hit one surface, sometimes the other.  

 

In the case of, say, a table leg resting on a floor, it will only be an issue if the surface is visible (a transparent table leg, for example.)

 

[Sampdoria]

An old conundrum solved! :)

[Marc Chaumier]

That's what we do when we model a volume of a liquid in a transparent glass. Not in the case of the water in the pool. In this case we have to use a 3D face (alaways seen from above). right?

[Roy Hirshkowitz]

Yes to the swimming pool.  This 3d face is not tagged as thin.

 

Complex transparency like liquid in a glass isn't handled very well in nXt.  The best current solution is probably to leave small gaps between the glass and the liquid.  This is physically incorrect for liquids but will work OK for now.

[Marc Chaumier]

Thanks, Roy. Are you going to work on these physical phenomenons? It's not very important for my work, but just to know...

[Roy Hirshkowitz]

Maybe at some point.  

It's quite difficult to even model this correctly-- solid modeling doesn't even really work for this-- you need intermediate boundaries within the solid.  I'm not even sure if you could do it with Rhino.  Materials also need to be defined as interfaces-- for example Glass->Liquid or Glass->Air.