Dispersion

[Ed]

No, the HDRI is not multicolor.

The color in the diamonds is the dispersion.

An excellent article on dispersion, published by the GIA, is here:

http://www.gia.edu/research-resources/cut-microsite-pdfs/diamond-optics-part-2.pdf

The last three pages are especially of interest for anyone who renders diamonds.

Ed

[Johnjoti]

No, the HDRI is not multicolor.

The color in the diamonds is the dispersion.

Share please HDR and scene

An excellent article on dispersion, published by the GIA

That's so!

I hope Keyshot developers will read this article and draw conclusion in respect of diamond material

[Ed]

The HDRI is one I spent several hours developing, and because it is an asset of my company, I'm unable to share it.

In my opinion, an HDRI for diamonds needs 8 to 12 separate lights - much like the multiple mini-spotlights used to display jewelry in a store.  The large white panels in your example HDR are a step in the right direction, but these large areas of even light are not going to give the best result.

Finally, I don't know why you are posting renders from another program.  Are these supposed to be the ultimate example of a diamond?  They look far too colorful and saturated.  Even the KeyShot examples I posted have the dispersion set too high - I exaggerated the ABBE setting to make the point you can adjust KeyShot to have as much as you want.  When I look at photos from the top diamond sellers (and they can afford the best photographers) I don't see the exaggerated dispersion as shown in your examples.

Don't blame KeyShot for not trying to produce a result that is artificial.  The fire in a diamond is the result of movement - either the diamond, the lights, or the observer.  In a static situation, such as a single frame render, the dispersion is subtle.  If I could animate the turntable in my render, the fire would be dramatic. 

Good luck and keep experimenting with various HDRs as this is a major factor in how diamonds will turn out.

Ed

[Robert V.]

Could you tell us if you used special software for creating your HDR?

[KeyShot]

Johnjoti,

Diamonds are a dielectric material, and the physics is quite simple. KeyShot uses the exact equations to compute reflections and refractions in diamonds. The abbe number is used to compute the wavelength dependence for refraction, and finally the transmission color take into account absorption within the diamond.
You really do not need much else to describe a diamond. The article talks about the fire, which you can control with the abbe number. If you make the abbe number very low then you can create the exaggerated fire effects that you are looking for. Also, remember that the position of the lights are critical to the appearance of diamonds. You cannot compare rendered results with other programs without having precise control over the lighting.

I should also mention that KeyShot features the only rendering and lighting engine that have been verified by CIE (CIE 171:2006,Test Cases to Assess the Accuracy of Lightning Computer Program) as computing the correct lighting. The report is available as CIE 171:2006 report, 2006, ISBN 978 3 901906 47 3. Please note that several major rendering packages have been tested against these CIE testcases, but only Luxion's rendering engine was found to compute lighting correctly.

-- Henrik

[Ed]

Could you tell us if you used special software for creating your HDR?

I have Photoshop and HDR Light Studio. But for HDR creation & editing in my type of work I like to use the image editor in Artizen HDR ver 2.9.  It supports 32 bit .hdr format, has layers, and tone mapping.

Ed

[Yanchen]

Johnjoti

just bash and bash...it's not our problem if you can't use the program well. Upload your scene and I will show you how to render that right in keyshot. Abbe value is also dependent in your model's thickness so the units must be accurate.

Keyshot2
HDR



Аlternative soft
HDR





Keyshot2
HDR



Аlternative soft
HDR

Upload your scene and I will show you how to render that right in keyshot

Ok, show my excellent render please, or the same as my render "alternative soft"
use this HDRI:





Two scenes and both HDRs
http://rapidshare.com/files/417755617/scene.rar.html

Swanky!!
What do you call this software?

[Johnjoti]

What do you call this software?

Write to PM or e-mail

Keyshot
I set against Keyshot2 to another soft. I used the same settings and same HDRI
Two scenes and both HDRs http://rapidshare.com/files/417755617/scene.rar.html
In your program stones seems gray and not clear.
ABBE number be not answerable to get the beautiful fire effects
They can surely do better?

Keyshot2

Аlternative

Diamonds are a dielectric material, and the physics is quite simple

Is it possible heavy to create additional material diamond? At least the same as render alternative soft?
That'll do the trick!

I should also mention that KeyShot features the only rendering and lighting engine that have been verified by CIE

Probably they had a substandard diamond

[JeffM]

Here are some samples of what effects different environments can have on a diamond model.

The diamond model was rendered twice in each environment. Once with 0 abbe (off/no dispersion) and the second time with 25 abbe (lower abbe numbers show more dispersion).

First is an almost purely diffused studio environment leading to very little contrast and almost no "fire" (thumb nail of the environment shown below the images):
0 abbe

25 abbe



Many small spots of light from the ceiling and a contrasting background lead to much more fire:





This diffused environment has a more typical amount of contrast, but the lack of small points of light leads to less fire:





Adding a brighter light from the side brings out a bit more fire in the diamond:





A high contrast studio that you might use for chrome creates an interesting look:





You can also exaggerate the dispersion/fire effect by setting a lower abbe value. Here's a couple shots using some of the environments from above with 10 abbe:




I hope that helps illustrate the point that diamond renders are not automatic. They are a combination of lighting, camera angle and material settings (abbe number/ior).

[Johnjoti]

Thanks JeffM
It is interesting and instructive

But create additional material diamond pleeeeeeeeeaaaassssse!!!!!!!!!!!!!!

[JeffM]

Thanks JeffM
It is interesting and instructive

But create additional material diamond pleeeeeeeeeaaaassssse!!!!!!!!!!!!!!

Are you looking for additional white diamond materials with varying levels of "fire"? Are you trying to get anything else out of your diamond renders that the default diamond material is not accomplishing?

Just let me know and I'm happy to help.

[Johnjoti]

I've been experimenting with different settings of diamonds and used different HDRI. embedded material is a diamond does not give the result that I expect.
I saw a lot of very expensive large diamonds. If the diamond is of good quality it shines beautifully saturated multicolored fires
At this time, your material does not allows to customize a beautiful rich fires. It looks blurry or gray, abbe works poorly (((((

Please add a mat is the same as (alternative shoft)

Look diamond works in the alternative program.
Two scenes (Keyshot & Alternative) http://rapidshare.com/files/417755617/scene.rar.html

[Johnjoti]

At the present time their diamonds be best-of-breed.
Theirs mat is easily customizable for any HDRi & have effect

[ben10]

about the contrast and shadow...you can play with the gamma in realtime tab and environment tab...right balance will create the effect you're looking for...there's no fixed settings...you should also reduce pixel filtering to 1-1.2....about that alternative renderer you don't need that much tweaking in settings coz it is somewhat unbiased or maybe a marketing strategy...maybe it's using brute force or path tracing idk....but you must admit it is slower....check out zigarettos and ed's images of diamond they are really impressive...you may ask them to share their scene and you may take a look at how they made that scene.

[Johnjoti]

Сonvulse!!!!!!  


sorry  

and yes I work with small diamonds, but not 2 carat

Ed

Ed does not work with large stones. I guess he can't seen

"The tune" goes something like this
http://www.coldiamond.com/cross-of-light-diamond.html

try and do it in keyshot!!! and show us

ABBE, HDRI, reduce pixel filtering...

LOL
I don't think that's good enough.