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Help with some glass material

Posted: Wed Jul 30, 2008 12:22 pm
by nikolatesla20

I have here a glass cube, with a plane underneath it.

The glass is a specular material, IOR 1.51, transparent, with RGB absorb of white (all sliders all the way down so it doesn't absorb)

I am using an HDRI EXR environment map, "Campus_probe"

Wondering if anyone can help me get rid of the artifacts circled in the picture - not sure what is causing them. They seem to be there even with other EXR maps.

I'm using Blender 2.45 with Indigo 1.0.9 and blendigo that matches (1.0.9)

The cube has a bevel modifier on it to create the bevels. The behavior is the same whether I "apply" the modifier or not.



Posted: Wed Jul 30, 2008 12:37 pm
by zsouthboy
Those look like reflections of high-frequency data in the .exr map (trees, perhaps?)

Posted: Wed Jul 30, 2008 12:55 pm
by nikolatesla20
I thought perhaps they were, but it does it in two different EXR maps.

I've found a studio lighting EXR map so I'm going to try that and see if it gets rid of it.


Posted: Wed Jul 30, 2008 1:00 pm
by nikolatesla20
Hm no it seems to still be there. I wonder if it is some other settings I need to make for Indigo.

I've attached the IGS file, you can use any EXR map and it seems to do the same thing..

Also attached is EXR map for the studio..


Posted: Wed Jul 30, 2008 1:12 pm
by OnoSendai
I think it's just noise, from light bouncing around inside your object.

Posted: Wed Jul 30, 2008 1:20 pm
by Borgleader
Well it seems to be "selective" since it appears more in some areas. But it could also be a combination of both.

Posted: Wed Jul 30, 2008 1:38 pm
by CTZn
As Ono said; it's called TIR (total internal reflection). It's a physical effect not an artifact. Try without bidir, the noise should reduce faster.

Posted: Wed Jul 30, 2008 1:47 pm
by nikolatesla20
Will I still get proper caustics without bdir though?

THanks for your help guys.


Posted: Wed Jul 30, 2008 1:58 pm
by CTZn
I bet you will.

This effect is caused by the reflections inside the glass panels, when light is trapped within due to reflection angle being to low for exitance, a bit like when to mirrors are facing.