I have considered the value of letting the user specify the color to use 
when max trace level is reached, although I figured it would just be the 
background color. In a way it makes sense, since if a ray ends up not 
hitting anything that is what the program assigns as the color of the pixel, 
correct? Might make more sense to use the background color as the last value 
and then still calculate the average to reduce the degree of wrongness.


"clipka" <nomail@nomail> wrote in message 
news:web.497e7f655867a2bd122a8da90@news.povray.org...
> I'm just brooding over the issue of max trace level and ADC bailout.
>
> If I'm not mistaken, at the moment this is handled such that a ray that is
> either "too deep" or is unlikely to make much of a difference is truncated 
> to
> black. Which is not ideal, especially when dealing with low max trace 
> level and
> high bailout values (or low weights), as it happens during radiosity 
> sample
> gathering.
>
> I have a few ideas that could help improve the results in such cases:
>
> (A)
>
> Have the user specify a "cutoff color", to be used instead of the current
> default black when a ray exceeds the max trace level or ADC bailout limit; 
> this
> way, the color can be adapted to the scene, e.g. for a scene dominated by 
> a
> bright blue sky the user could choose a rather bright, blueish color.
>
> (B)
>
> Stick to the black, but automatically "boost" each pixel that has suffered
> "cutoff" according to the "lost weight"; e.g. if during tracing for a 
> pixel one
> ray is "cut off" that would have contributed an estimated 10% of color to 
> the
> pixel, and another that would have contributed 5%, multiply the resulting 
> pixel
> color by 1/0.85. (Alternatively, such a correction could be applied at 
> each
> "fork" where a ray is cut off; however, it would then be unable to catch 
> cases
> where multiple "forked" rays are cut off.)
>
> This may still be wrong, but hopefully not as wrong as the current 
> "blackout".
>
> (C)
>
> Borrow some approach from path tracing: If at a "fork" both rays would 
> drop
> below the bailout threshold, but together they would still be above it, 
> roll a
> dice and trace one of them.
>
>
>

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