Time Now, for Dawn's Stupid Questions!

Last night, as I sat at the table with the cousins, playing D&D, I was
also working with POV on my laptop.  One of the cousins said "Hey, cool,
can you make me a lightsabre?"

So I hemmed and hawed for a moment, and came up with a way to do it.  I
CSG merged a sphere on the end of a cylinder, filled the cylinder with
emitting media, did a cylindrical pattern with a density color_map to
create the blade, and discovered something kind of odd...

If I do a color_map [0.0 color White ][0.5 color Green ] [1.0 color
Black], and I have a black background, I get pretty much exactly what I
expect to see... a white core, with the green color around the 'blade,'
and both of them fade into each other, and then into extinction.  As I
say, what I expect to see, and a pretty good image of a lightsabre blade.

But (and I did this first, found it didn't work as expected, and went
with the above solution) if I substitute "color Clear" for "color Black"
in the color_map, I get an object that appears clear all the way through!

Why do it do that?  How can I make it not?  Source code posted in p.t.scene-files.

-- 
Dawn McKnight      | "Who cares what the hipbone's connected to? I'm in Neurology!"
McK### [at] maccom   |					-- Justine Devlin, M.D.

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