Nathan Kopp wrote:

> > 6.)  If I shoot white light through a 60 degree equilateral triangle
> >    should I be getting prismatic dispersion on the output ? I know
> >    Darrens patch addresses this internally but was wondering about the
> >    effects of external out put with no method of assigning an internal
> >    dispersion characteristic.
> 
> I have implemented dispersion, but there's no default spectrum.  If you
> creat your light source like this:
> 
> light_source
>   <10,10,10>
>   color <1,1,1> // this will be replaced, but the parser is a hack right
>                 //   now, so it is still required
>   color_map{    // here you define your light's spectrum
>                 //   this color_map acts like "average":  the first value is
>                 //   weight (intensity), the second is color
>     [1, <.5,0,0>]
>     [1, <.2,.2,0>]
>     [1, <.3,.3,0>]
>     [1, <0,.5,.5>]
>     [1, <0,0,.5>]
>   }
> }
> 
> Notice, the color map entries added up to <1,1,1>.  This spectrum will
> probably look bad (I made it up just now), but you get the idea.

  Ah ! Undocumented features surfacing. Any other little easter eggs
hidden in there that you haven't mentioned ?

 
> > 7.) On the same topic as above should light bend in accordance with
> >    the natural laws of physics or is the photon model used in the
> >    patch more of a visual gimmick than a relativistic lighting model.
> >    I have observed unnatural behaviour in three different prisms
> >    constructed using differing methods. Each was tried with a wide
> >    range of both photon related parameters and options as well as
> >    changes in refraction, reflection, and  the filter/transmit values.
> >    None of the computer based models matched a physical prism I have
> >    been using as a reference for comparison.
> 
> It does follow the laws of physics.  (not relativity, though.)  Make
> sure you use an IOR value that matches the real prism.
> 
> -Nathan Kopp

 I tried everything from ior 1.0 to 4.5 and had little difference in the
refraction of the light. I will continue with my experiments and see
where then I am at fault. It may be a that the internal reflections are
not high enough or the material specification is wrong.

 On a side note did you by any chance see my questions in the new
unofficial patch directory concerning some of the other features
of your patch ?

-- 
Ken Tyler

mailto://tylereng@pacbell.net

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