Why my glass refraction is black?

[pentool]

Hi,

I'm experimenting with creating glass/clear plastic and read the tutotrial on the aversis site about glass (http://www.aversis.be/extra_tutorial...ettings_02.htm). However, as you can see on this render (just low-res), the clear glass material has lots of black in the refractions and I don't know why.

All the other glass materials (blue and yellow) are the same, except for their fog color, and yet the white/clear glass is black. I've played around with so many variations of different settings in vain, that a this point I just gave up.

The objects are in a box, so it's not reflecting the environment of a black "nothing". There's a vray light above (rectangular). I've also posting my material settings, which - as I said - the same for all glass except for the fog color.

Thanks for any help.

--LES

[jonnybefree]

hi pentool,
try to increase the refr. max depht. in your glass material

[pentool]

Nope. I've tried changing those values for both refract and reflect even up to 50. Nothing.

[jonnybefree]

hmm, double faces? mesh is penetrating?

[pentool]

"mesh is penetrating"? what does that mean? (...sorry, I'm new They are just simple cylinders.

[jonnybefree]

are those cylinders sitting inside the other mesh a bit?

[Clifton Santiago]

The problem could be either because your environment color is set to black, and/or because your reflection and refraction exit color is black. Change each to another color and re-render to identify.

[joconnell]

It's a problem that you get with raytracers and often geometry that is imported from cad programs. What johnny means by interpenetrating is that you may have two polygons sitting in the exact same place - the cylinders sitting on the top of the yellow object may have to be moved up by a tiny amount. You may have some of the polygons of the yellow object sitting in the exact same plane as the bottom of the cylinders - The raytracer wants to work out how to bend light going from one glass surface through the clear glass cylinder, through the air and into the yellow object but if there is no gap between the two it can cause these raytraing errors where you get black faces.

Try moving the cylinders up a tiny amount and see if it fixes it.

[pentool]

Thanks a lot guys for the tips! Yes, indeed the problem was that the cylinders were sitting right on top of the yellow mesh. Moving them up slightly solved the problem.

I wondered why the long clear stick didn't have the problem, but now it makes sense, since I "accidentally" didn't placed it such that it would touch the yellow glass so that one didn't exhibit that issue.

Thanks, again!