Acadia, whoa. I was out of town and couldn't jump back in to reply.

The last bit you said about Matmatic is confusing to me, since Matmatic is HOSTED ON YOUR SITE remember? It's just one zip file. All those other posts you may be referring to are not part of matmatic. They are examples of things I come up with over time and are not part of Matmatic at all.

Anyway back to the diamond. I guess I wasn't clear in my first post. As a result, you made a mishmasm of the chromatic reflection material posted above, and the simple fresnel material in my article. What I was trying to say was this:

1. Go to the fresnel thread and try either the simple glass shader (fresnel node and nothing else) or try my 5-node version, with and Index of Refraction of 2.4. Either would work, but my version can be used for ruby and other colored gems, whereas the simple fresnel won't look real.

2. If you're not happy enough with the shine, it is because of lack of total internal reflection. This is less important in ruby and other dark gems, but very very important in diamond and lightly colored gems. To get that look, modify the gem so it has a new material zone on the bottom facets. On those facets, attach either a) a perfect mirror shader (just a reflect node), or b) my chromatic mirror which I showed above.

Again, 90% of the diamond's appearance is actually reflections of the scene behind and above the camera.

You do not have to use a sky dome if you want a transparent background - I just suggest a dome because it is the easiest thing in the world to set up, as you can see it from every direction. I use a sky dome so often I made it part of my default Poser scene. File-New = skydome and ground. 

Anyway, you don't want one, fine. But you have to have some strongly contrasting stuff to reflect in your gem. Try placing giant white squares or balls all around the gem scene, just outside the view of the camera, but in view of the gem. If the gem is facing the camera, you can probably just put a couple big one-sided squares behind the camera. But make sure they are WHITE, meaning even if the light doesn't hit them right, they must GLOW!

Don't get frustrated! 

I don't have my Poser gem stuff here at home - when I get to work on Monday I'll post complete materials so you don't have to guess what I mean or try to copy mat room screen shots.

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Renderosity forum reply notifications are wonky. If I read a follow-up in a thread, but I don't myself reply, then notifications no longer happen AT ALL on that thread. So if I seem to be ignoring a question, that's why. (Updated September 23, 2019)