CB and LL:

Nice. My cult grows. LOL

You guys got it right - must have been paying attention. IBL can make shadows, but they behave like an infinite light. Good for outdoor IBL with a sun in it. Not good for indoor multi-light scenarios. Better to use IBL for fill and use actual Poser lights for distinct, strong light sources.

Suthers:

A math cultist? I will prepare some diagrams. (I will first write a program to generate said diagrams easily. I've been wanting one for a long time. There is some really fascinating stuff in math for CG, but most people cannot visualize it like I do in my head. I need a very fast math function interactive diagramming tool. Have played with a few free ones - I see flaws. Will write my own. Be back later).

In the meantime, here's a clue, and you should be able to work out some of the rest. Viewing the radial cross section of the probe as a function f(x), the derivative f'(x) = tan(x).

Some thought provoking questions for you:

What is f?

What is the value of f(pi/2)?

Why is f(pi/2) interesting or important?

How long should the probe really be?

What did I do about it and why?

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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)