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Hopper
08-18-2008, 10:03 PM
Hi guys,

I'm tring to texture a gem (made by the gem primitive), but no matter what I do it winds up looking like clear glass. I tried using the Dialectric Node also but it turns out just as clear.

Here are my settings...

Refraction index: 2.14
Diffuse: 10%
Specular: 75%
Color Highlights: Off
Glossiness: 64 (Medium)
Reflectivity: 20%
Transparency: 100%
Color Filter: On
Smoothing: Off

I'm using my HDRI as my reflection but it's just not getting it. Any suggestions?

Thanks

jameswillmott
08-18-2008, 10:32 PM
You could use one of the materials with Dispersion to get some coloured refractions happening, you'll need quite a few ray recursions as well...

Nangleator
08-19-2008, 07:28 AM
I was just going to say Dispersion. Make sure there's some non-zero amount of roughness, then add lots of dispersion. Gems get their look from lots of internal reflections, but you might be able to cheat it with a refraction image instead of a high RRL.

Those internal reflections can make the render crawl.

Gui Lo
08-19-2008, 07:34 AM
Those internal reflections can make the render crawl.

True.
Play with the Ray Recursion Limit to reduce render times. A low setting can be used at first to get the look and them increase it for the final render.

OOZZEE
08-19-2008, 07:40 AM
you could always try these

http://www.auroragrafx.com/LWresources/LW_Presets/GemStones/Presets_Gemstones.shtml

JeffrySG
08-19-2008, 07:58 AM
You can also fake dispersion by rendering 3 images with slightly offset indices of refraction
That's very interesting! Never heard that tip before!

Andyjaggy
08-19-2008, 10:15 AM
Well if all your using is an HDRI and no lights then the spec values won't have any effect anyway will they?

Simon
08-19-2008, 02:18 PM
Just like the real thing, the angles of the gem's facets are crucial in getting lots of internal reflection and hence sparkliness. Diamonds are cut with a lot of shallow angles for this reason.

Attached is a simple test scene I made a while ago using a plain dielectric material for the gems. I used (I think) models from this site which even tells you what refractive index to use for each one:

http://www.3dlapidary.com/HTML/Stones3.htm

... and the HDR probe I used (not included in my scene) I got from the below site, it's the one called beverlyHills_sun_probe_FINAL.hdr:

http://www.unparent.com/

Hopper
08-19-2008, 06:04 PM
Thank you very much!

I am going to go through every one of these and see how it goes. I'm especially interested in Neverko's solution... How did you come up with that anyway? Those kind of solutions can't possibly be accidental.. :)

Oh .. and I eventually figured out the specularity thing... It's now glued to 0. I changed the HDRI to a solid white PNG and it started to look better.

I never even thought to crank up the RRL. (and that's why I'm still a noob). :D

Thanks for posting the gem scene Simon. Real examples to learn by are awesome.

ingo
08-20-2008, 04:15 AM
Hi guys,

I'm tring to texture a gem (made by the gem primitive), but no matter what I do it winds up looking like clear glass. I tried using the Dialectric Node also but it turns out just as clear.

Here are my settings...

Refraction index: 2.14
Diffuse: 10%
Specular: 75%
Color Highlights: Off
Glossiness: 64 (Medium)
Reflectivity: 20%
Transparency: 100%
Color Filter: On
Smoothing: Off

I'm using my HDRI as my reflection but it's just not getting it. Any suggestions?

Thanks

Hmm, seems you got your settings from the old tutorial from Dave Jerrard. If you have that tutorial just read on, its all explained there.

And don't forget the fresnel effect !!

Hopper
08-22-2008, 08:55 PM
Hmm, seems you got your settings from the old tutorial from Dave Jerrard. If you have that tutorial just read on, its all explained there.

And don't forget the fresnel effect !!
You are absolutely correct sir. I am but a lazy IT guy, thus Googling "Lightwave gem texture render" was faster than futzing around with settings for three hours. :)