I was giving the technical description of what it's supposed to be
doing. :)

You did seem to 'fudge' the colors towards making yellow in the middle,
which seems to be the accuarate way of doing it.  I don't know if anyone
will ever bother for a physically accurate representation.  I know I
sure won't.

I doubt most people will notice small inaccuracies unless they are
getting a PHD in optical physics, and those people shouldn't be turning
to POV to do their dissertation anyway!  ;-)

-Mike

Daren Scot Wilson wrote:
> 
> You know a patch is big hit, when other people give the correct answer
> long before the patch author gets around to reading the question  :-)
> 
> Just want to clarify some details.   The IOR in the dispersion patch is
> an exponential function of color number.  By color number, i mean i'm
> counting subrays that are traced, from 1 to disp_nelems.   In other
> words, each subray uses an IOR a certain ratio higher than the previous
> subray.  This is not based on physics, but ease of implementation and
> good looks.  IMHO, a linear function did not look good enough.   Real
> physical materials have a variety of dipserson curves, which would be
> fun to model, but I use povray for art not physics.
> 
> Each subray is traced, and contributes some amount of a pure hue to the
> sum.  The formula for converting the nth ray into a color is purely
> ad-hoc, chosen to look good, again no real physical laws were refered
> to, and to match some mathematical criterea, mainly that it had to sum
> all-equal subrays into pure white.  For looks, I want a nice yellow, and
> violet at the low-wavelength end.
> 
> At no point in the process do i calculate or use wavelengths.
> 
> With the  source code out there, it's just a matter of time before
> someone tweaks it to behave more in accordance with real optics.    I'm
> too lazy, and have a totally different ray tracer for good physics
> rendering.
> 
> --
> Daren Scot Wilson
> dar### [at] pipelinecom
> www.newcolor.com
> ----
> "A ship in a harbor is safe, but that is not what ships are built for"
>                                             -- William Shedd

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