andrel <a_l### [at] hotmailcom> wrote:
> I think I agree with Thorsten and Christoph that 3.6 behaviour is
> mathematically correct and that 3.5 had a bug/feature.

  The 3.6 behaviour might be *mathematically* correct given some
premises (which might not be realistic). However, the 3.6 behaviour
is not *physically* correct, which is the most important thing here
(but neither is the 3.5 behaviour, for that matter).

  The raytracing algorithm tries to simulate a photographic film which
is hit by light. The aim of POV-Ray is photorealism, not light absolute
intensity measurement at each pixel.
  If the goal of the rendering was to measure the intensity of light
hitting each pixel, the 3.6 antialiasing would be more correct than 3.5,
but it would not be perfect either: Brightness is clipped to a certain
maximum value, which renders even this goal useless.

  However, that is not the goal of POV-Ray in the first place. The goal
is to simulate photorealism.
  What happens when light hits the film of a camera, and this light is
much more intense than what the camera/film is configured for? The film
gets overexposed at that point. Overexposure manifests itself by color
bleeding: The spot which is too bright will spread to its surroundings in
the film.

  So neither the 3.5 nor the 3.6 antialiasing methods are physically
correct.
  The question which remains is: Which one produces better images?

-- 
#macro M(A,N,D,L)plane{-z,-9pigment{mandel L*9translate N color_map{[0rgb x]
[1rgb 9]}scale<D,D*3D>*1e3}rotate y*A*8}#end M(-3<1.206434.28623>70,7)M(
-1<.7438.1795>1,20)M(1<.77595.13699>30,20)M(3<.75923.07145>80,99)// - Warp -

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