Double refraction? Brighter tones

[Razorsbhc]

Hi

I`m trying to render a nice and looking Sapphire gemstone, But I`m having some problems with the internal refractions of it.
I don`t get that the right color contrast, My "3D" stone only contains a average blue tone, But in the Photo reference there are some really bright light blue tone.

Does anyone knows how this can be made? Tips/Tricks are welcome
I have tried to use absortion but it only make it darker,

Is this feature/setting avaible in Octane`s material? It`s the direction of the IOR,
Birefringence
http://en.wikipedia.org/wiki/Birefringence


Max depth: 15, Patch Tracing
Lightsetup: HDR, Some white and black gradients.

Material Setup:
IOR: 1.7
No Absortion/Scattering
Reflection: With Falloff Texture
Dispersion coeffient: 0.018

[roeland]

The brightness and contrast in the image depend for a large part on the lighting and the cut of the stone.

These renders usually look better when using absorption instead of setting a transmission color. When doing so set the transmission and reflection to 1.0, and set absorption to red or yellow. You don't need a falloff texture for reflection, the specular material already calculates the Fresnel effect.

Birefringence is not available in Octane.

--
Roeland

[Razorsbhc]

Ok, I will try the absorption medium, last time I tried it I had to give it a value of 15000-3000 to even se any different in the colors, What's strange because my gemstone is about 2mm, and the scale value is in meters, right?

0,001-0,005. Value would be more reasonable, in my scene setup.

Unit setup in max:
1unit=1mm (as told before, octane rescales it to meters when exporting to render, right?)

By the way, Thanks for the reply I really like to hear from you guys who made this fantastic render.

/Johan

[profbetis]

Your gem looks very very blue.

is it exactly 100% blue? no red or green? It could be that some of those highlights are being crushed because of the pure color. I suggest mixing a very small amount of red and green to help those bright highlights escape.

Alternatively or also, go to the camera response and try turning up the "saturate to white" control, this makes very bright saturated colors have less saturation so they appear bright like they should be.

[roeland]

Very small objects with absorption will appear less colored because the light travels less distance within the object, so you need a higher absorption to get the same color. An absorption value of 1.0 means about 63% of the light gets absorbed after 1 meter, 1000 means 63% gets absorbed after one millimeter. A value of around 2000 sounds reasonable for this gemstone.

--
Roeland