coplanar or overlapping workflow

[Rico_uk]

Hi all,

I just have a quick question about the procedure / workflow for transmissive objects such as glass and how their faces sit on top of other objects. For example, if a glass box sat on top of a diffuse surface, would the faces need to be co-planar, ie. touching perfectly, or should the box be raised slightly above the surface?

Also how would this apply to an example like a liquid within a glass. I know in some biased renderers you should slightly overlap in the faces, would this be the case with octane, or would you have the faces either co-planar or have the liquid mesh slightly back from the glass mesh so that light can enter and exit the glass before entering and exiting the liquid. I imagine being physically correct it will be the latter, but thought I'd ask the question as I can't find anything on this in the manual or on the forums.

Sorry if it has been covered and haven't found it, it's not an obvious thing to think of a keyword to search for.

Mike

[Rico_uk]

its ok, i finally found some stuff in the forums by Philbo

[steveps3]

don't leave us in suspense.

[Rico_uk]

well there's these other posts:

http://www.refractivesoftware.com/forum ... f=23&t=649

http://www.refractivesoftware.com/forum ... ass#p64699

But having read them it's not much clearer. I think it's a 'horses for courses' thing, so just whatever works for your scene as there isn't a 'physically correct' way to do this at the mo (unless I've missed the point). I think inverting some nirmals helps light to pass through two meshes easier inside the renderer, no idea really. I'll stick to the method of having a tiny air gap between the two objects, and the same for glass objects on a surface, I'll just raise it up slightly to let let pass fully through an object and out of the other side before doing anything else. This may well be wrong and I'll have to do some tests but seems to make the most 'physical' sense, and if render times increase I don't particularly care, Octane is pretty quick!

However if anyone can suggest a better / proper workflow that would be great.

[steveps3]

Sounds like you need to experiment with different techniques to see what works best for the situation.