I was making a render with a glass table and I wanted to use Baggingsbill glass-shader ( see the fresnel effect post in the nodecult at RDNA) but I didn't worked as wanted: Normally a thin sheet of glass gives only a small shift of the objects that are behind the glass, but the distortion I got was much too big! I set up a test render with a box, and two single surfaces and a red pole behind. the upper surface was rotated 180 degrees so it was  backfacing, I gave it all the glass-shader and rendered it. The result is shown above. What you see is that all objects give the same amount of refraction and that is not correct! ( IMO at least) What should happen is that the box should only give a small shift of the pole, and the backfacing surface should give a refraction to the other side. But that doesn't happen. I think this is a firefly fault: it simply ignores the back face of an object and what is worse: it ignores the normal of a surface. What should happen is that when a ray of light enters an object it should get an amount of refraction (depending on the index of refraction of the surface/shader) and when it leaves the object it should also get amount of refraction but the other way. Is it that I'm doing something wrong or is it another fireflybug (!), I tried everything: raising the quality of refraction, the amount of raytracing bounces, lowering the raybias, but npthing works.

If anyone has an experience with this or has a solution, I will be glas to hear it.

best regards,

Bopper.

Bug. Always has been.

Set the IOR on the Refract node to 1.02.

Note, what you said about ignoring the normal is not true. It does pay attention to the angle of incidence and refracts accordingly.

But the back-face does not do the inverse refraction.

However, try this: Set the front to 1.5 and the back to 1 / 1.5 = .6667. What happens?

*However, try this: Set the front to 1.5 and the back to 1 / 1.5 = .6667. What happens?

*Well, tried it, this is the kind of behaviour you should expect, (the box has 1,02 IOR by the way). But it is not as it should be, oh well, another item for the Poser 8 wishlist.

thank you BB.

best regards,

Bopper.

I just got it!

Set the back surface IOR to 1.0!!!

Poser does not pay attention to the facing direction, but it does look at the from/to IOR. Starting from 1, you enter the front and the IOR is 1.5, thus it turns. Now it quickly hits the back with IOR 1 (entering air now) and it turns back!

I'll try that, I tried to "correct" your shader with a N-node and math:pow -node but that didn't work.
Did you use two surfaces or a box?

regards.

B.

Yeah! that worked!, here are my settings to make it work, I suspect you did something similar.

Thanks again!

Best regards,

Bopper.