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Melmoth
08-11-2006, 03:12 AM
Hello, please excuse my english...

I try to simulate a birefringent crystal with the node editor and some anisotropic refraction nodes... but i don't manage to render this kind of refraction.

any suggestions ? Is it possible ? :grumpy:

Help me please in my quest

Melmoth

starbase1
08-11-2006, 03:17 AM
Can you explain what a birefringent crystal is?

Melmoth
08-11-2006, 03:27 AM
Sure,

http://en.wikipedia.org/wiki/Birefringence

A birefringent material has 2 IOR and that's my problem...
Can I mix or add 2 IOR ? Can I render 2 IOR ?

...

Weepul
08-11-2006, 03:42 AM
A birefringent material has 2 IOR and that's my problem...
Can I mix or add 2 IOR ? Can I render 2 IOR ?
Absolutely. Use a Mixer node to blend two Refraction nodes with different IOR values set in each. Connect the Mixer node's output to the refraction shading dot.

In testing this, I wasn't getting a double-refraction effect as strong as in the example image, and I seem to remember from physics classes that the refraction is angled slightly. To get this effect, I created a skewed set of normals for the second refraction node that will angle its refraction. I'm attaching a screenshot.

Hope that helps!

Melmoth
08-11-2006, 03:55 AM
Thanks Weepul,

I didn't try a "normalize" node yet... that was my fault.
Thanks a lot !

I'll make the first french tutorial about birefringence rendering thanks to You...

"Live Long and Prosper" said Shanok

Melmoth

Melmoth
08-11-2006, 04:55 AM
I tried my render with a Light Direction Vector... seems to be more "physic".

Thanks a lot Weepul !

35739

Melmoth
08-11-2006, 02:15 PM
for those who speak french, here is the tutorial about birefringence :

http://www.ecoles-bordeaux.com/spip.php?article85

sorry for the others, watch the pictures !!! 8/

Melmoth
08-14-2006, 03:47 AM
I have updated my tutorial with a trirefringent glass ...
I have applied a color to each of the 3 IOR and simplified the Nodes...

http://www.ecoles-bordeaux.com/spip.php?article85


If u have any question