Dispersion

Started by Johnjoti, June 28, 2010, 07:34:20 PM

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Ed

#15
Here is another scene using the same HDRI as my prior posting.  This time I tilted the diamond up toward the light, and I added a small rectangular plane with a white emissive material to act as a bounce card. The emissive object (set invisible to the eye) does not affect the color, but just allowed me to brighten up the diamond a little independently of the HDRI.

The top render has the diamond material ABBE=14.  The bottom has ABBE=1.5 to show the extreme end of the range.

Diamonds are complex, and you have to find the right HDRI and sweet spot to illuminate it. This lighting would probably not be correct if the diamond were mounted in a ring shank.  It's difficult to find a sweet spot that illuminates both the diamond and the ring shank correctly at the same time.

So for a mounted diamond I would make two render passes: Hide the ring shank and adjust lighting for the diamond, and save the render.  Then un-hide the ring shank and adjust the lighting for the metal, and save the render.  Combine the two images using layers in Photoshop.  

Using this technique you can even use two different HDR environments - one optimized for the diamond and one optimized for the metal ring shank. Same idea is used by many jewelry photographers - an intense light for the diamond shot and softer lighting for a second shot to prevent blowing out the metal shank.  Mask in Photoshop layers to reveal the brighter diamond.

It's not complex and the car guys do it all the time to get the best lighting for the car glass VS the paint VS the chrome, etc.

Ed

KeyShot

Hello John,

The diamond material in KeyShot is physically based. If you take a real diamond and illuminate it with blue light it will be blue. You mention iridescence. Diamonds (at least in the normal cut and sizes) do not exhibit iridescence. The color shift you are seeing is purely due to dispersion. Dispersion does not change the wavelength of light but simply spreads it out (disperses it). If your light is blue then spreading it out will not create green or red. To get the fire in diamonds it is important with good lighting (jewelry photographers know that very well) and I would recommend smaller white lights for this purpose.

-- Henrik

Johnjoti

#17
Hi all!
Sounds like a plan Ed!
I like the idea of using different HDR for separate coverage of diamonds and gold. Imagine that I want to do animation with a diamond ring. It will take 100 frames for a diamond, and 100 personnel for the gold can be night time. Then process them in Photoshop, this is another day!
Is it possible to use simultaneously different HDRs in the Keyshot ? One of
optimized for the layer with diamonds, the other a layer of gold? If not, Will there be such a possibility in the near future??

Henrik
All still have a need to review the material diamond. Something is amiss...
Colored fire in diamonds look as if they watered down white paint. They are not clear, diluted color

"The diamond material in KeyShot is physically based" Maybe this is too much? May be a create additional material "fake" ? for concerned about the jewelry photographers???

Thanks


Johnjoti

Dear KeyShot. What do you make of this idea?

ben10

1. Weird, you have provided an actual pictures that uses the same color and then you will insist that keyshot should not use that kind of colors? It actually match some of the pictures you've provided
2.if you tried to lower pixel filter size to 1, the default is 1.5 and play with gamma in environment and gamma in image/realtime tab you will achieve a very sharp render....you also need to have a very good hdri and very good model

Ed

#20
Just for fun I made a render with the diamond set in a brushed finish titanium band.  One render pass and no post work.  

I adjusted the ABBE down until I just started to see dispersion (I probably went a little too far).  I could have gone further, but I think that would not look natural at all.  

A 400% enlargement in PS of my image shows the color range in the stone.  Again, the HDRI is a big factor for diamonds.  I'm happy with the result after a little experimentation.

It's interesting to visit the Tiffany & Co. website and look at diamonds.  Little to no dispersion that I can find. 

Ed

Johnjoti

#21
Identical HDRs and material settings

KeyShot


Аlternative advanced software


It's ostensive proof.



KeyShot
Go forward!!
Get off the dime !!

ben10

Quote from: Johnjoti on July 02, 2010, 01:13:43 AM
turned out very nice diamond, but it's the best thing we can do keyshot.
You can use any HDR, can use any value Abbe, but will never see any green or aquamarine or orange ...




if you will not give a promise to make materials of good quality I am will forced to abandon work with KeyShot and will demand to return my money   :-\

Thanks understanding for my position

funny don't use green but you actually provided pictures that uses green...plus that blur in your render depends in gamma settings...decrease pixel filter size to 1.2 or 1...use a high quality hdr

Frank


Yanchen


ben10

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.

Ed

#26
I agree with ben10 - upload the model if you truly want help.

Can't say it enough times - there are a few variables involved, but it's not difficult at all.

Ed


Yanchen

#27
very nice Ed!!
+2

Johnjoti

#28
Ed
You used multicolored HDR on the image Random Diamonds 2.png? And metal will be multicolored? LOL

Johnjoti

#29
Quote from: ben10 on September 01, 2010, 05:58:11 AM
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




QuoteUpload 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