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Oh boy! Just what everyone wants. MORE BALL RENDERS!

I was just goofing around with dispersion effects and multi-layer BSDF. This was kinda fun.

I used the fake birefringence trick with a reasonably quartz-like material. Just to see what would happen, I made one of the layers with a mush shallower attenuation. Somewhat unsurprisingly, that didn't seem to make much difference.

The inclusions are just the gold complex IOR file with a tiny bit of bump map. There's a slight bump map on the quartz too, and a texture map controling the layer mixing.

That's nice, would be interesting to see what kind of caustics this would make.

Mmm. Yeah... Yeah it would!

I've set up a render to see what they look like now.

That's an afternoon of baking on it. The dispersion really slows it down.

I'm gonna let it go for a little while longer to see how it looks, but the caustics are certainly pretty neat.

(That line in the image is from my super crappy bump-mapping on the ground plane)

You can make the emitter smaller to get sharper caustics. Or have two emitters, one small for the sharper caustics and put the emitter in a bsdf set to be "ghost" (nd1, transmittance 255). Put the small emitter right in front of the bigger one. This small emitter will be invisible and not block the light from the bigger emitter.

Voidmonster wrote:

I used the fake birefringence trick with a reasonably quartz-like material. Just to see what would happen, I made one of the layers with a mush shallower attenuation..

I know this is a really old post, but the only one I can find referring to Birefringence (Double Refraction). You reference the "fake birefringence trick" can you elaborate or point me to a post detailing the trick?

It's about normal-blending multiple BSDF having different Nd.

For example:

Layer
...BSDF Nd 1.5
...BSDF Nd 1.8

You can check this demo material:
http://resources.maxwellrender.com/sear ... v2=0&tipo=