View Full Version : Diamond Ring

09-05-2012, 02:59 PM
Installed Bunkspeed Pro few days back.

Thought i should share my first render of this Diamond ring.
I am sure this can be improved to a great extent. so please give your feedback.
I am not happy with the way diamond has come out. how can i make it better?




09-05-2012, 04:28 PM
You can adjust the values, specifically the IOR and Abbe number values on gems to acheive the look you're going for.

Attached is a screen shot of a simple gumdrop primitive with diamond material appied. The only difference between them is the Abbe number value. From left to right: 0, 50..0 and 100.00. The IOR will also have a significant effect on how the material will look. Play around with them.

09-06-2012, 01:24 PM
Thanks a lot. will play around a bit and see if i can improve on it.

09-06-2012, 09:37 PM
For quick reference, note that a good starting point for a 'real' diamond is an ior of 2.5, and an abbe number of 54. Adjust both to taste. :)

09-06-2012, 11:18 PM
Diamond ior is 2.417 (give or take), and I find the best abbe anywhere between 35 and 50 - personal opinion, however the amount of color separation will be dependant on your camera focal length and lighting. Sharp light edges will show more color separation and more vivid rainbow effects than soft light or gradient lights.

Abbe is a personal preference. If you want more color seperation reduce the number, less color seperation increase the abbe. It is also dependant on geometry unfortunately. Perceptively smaller stones will show more color separation (botchy solid colors) than bigger stones (more "rainbow-ness"). Geometry size dependant abbe would be the next best thing... Hoping for this feature in BS 2.6 :p (with no stability issues of course :p :p ) You could workaround this by making two separate diamond materials. One for larger stones with smaller a abbe, and one for smaller stones with larger abbe. This would apply if you had a ring with small and large diamonds.

09-07-2012, 07:13 AM
IOR 2.5 and abbe number of 50 did make a difference to the diamonds.
But i guess i am not using appropriate lighting and hence i feel the diamonds still look dead.
It would be interesting to know how i can get a glint as the light catches.

09-08-2012, 06:55 AM
Any advice on how i can get caustics on the ground plane?

09-08-2012, 03:55 PM
I tried a few tests and I believe caustics are not working. In v. 2.4 (pre iray 3.0) it worked if you used smaller bright lights with your diamond close to a physical ground plane.

EDIT: It seems to be working however produces very subtle caustics...would be nice to control the intensity of caustics. In fact, i'm beginning to think they actually aren't caustics but merely the reflection of the ground plane off the lower part (pavillion) of the diamond.

Also for some reason (maybe because of the high intensity overhead white light), the diamond appears to have a purplish color.


I am not seeing any reflective caustics on this pure chrome torus either...


The scene was created with a 0 intensity environment, a physical emmissive overhead light at very high intensity (on the order of 10,000), and a very dark physical ground plane with rgb of 1,1,1.

09-10-2012, 10:18 AM
Caustics on a ground plane:

Create a plane, either in your modeling software or in bunkspeed.
Assign a material to that which is approximately, the more exact the better, the same material as your HDR ground. For most studios that will be between grey and white. Make sure the reflection amount is correct. More reflective means less ground shadow and more light on the bottom of your product.
You should be noticing caustics on this plane already.
Now just turn that plane to Faded. It renders as if it isn't there, but it's visible to reflections, refractions, and also picks up your desired caustics.

This technique is helpful any time you have a noticeably reflective/refractive material with camera rays pointing toward the ground as well. It's strange to have a white halo around an object where you Know it should be a dark reflection. Match the floor to your background color and that goes away.

09-10-2012, 03:14 PM
Andy were you able to get caustics? I don't believe its working. Maybe BS staff can chime in on this.

09-10-2012, 10:47 PM
Yes you are correct, caustics are not working right now. Iray 3 has an issue with caustics and the glass/gem material at the moment. We hope to have it fixed soon.

09-11-2012, 12:22 AM
Alas, along with iray 3 came some unaccounted for changes to materials, caustics was one that broke cause of it. I've got it fixed internally now but the change requires a much more thorough testing phase. Hopefully in a few days we'll have this version out in public. Apologies.

09-11-2012, 05:43 PM
@Ventare - Will caustics show appropriate colors if an abbe value is used on the glass/gem material, or will it be monochromatic?


09-20-2012, 06:48 PM
For now, caustics are monochromatic.

09-20-2012, 07:28 PM
Thanks David. When can we expect the next update to reincorporate this?

09-20-2012, 08:13 PM
We are shooting for next wednesday.

09-26-2012, 06:24 PM
Hi David, is it still a possibility you will have a patch ready for today?

09-27-2012, 05:21 AM
Yes, it went out today....