Severi Salminen wrote:
>> * Instead of shooting RGB rays, shoot photons of a particular wave
>> length, selected randomly from the spectrum of the light source at the
>> emission point;
> 
> Yes. This should be implemented at some point to enable accurate dispersion.

I should say that the weakness of this approach is that a surface that 
is supposed to be a uniform color will now appear to be a mixture of 
pixels that average to that color.

>> * A photon isn't drawn on the screen unless it hits the virtual film.
>> Then you calculate its RGB value, and add that to the pixel at that
>> point in the screen.
> 
> I start the rays from film plane so all rays always hit the film. I'm not sure
> if anyone does it the other way and how it works in practice.

So it traces from 'film' to light source, instead of the other way 
around?  I had assumed that it went the other way.  Maybe I could try 
writing a renderer that does that.

Regards,
John

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