"Peter Popov" <pet### [at] usanet> writes:

> The described algorithm is also suitable for true refractive caustics. The
> difference is subtle and is in the generation and usage of V[1..n]. Sample
> ray m hits O, refracts, hits it again at Pm, and leaves as m1 (that should
> be "m prime"). Vm lies on the reflection of ray m1 in Pm (but where exactly?
> I'll think of it) and it's color and brightness depend on two more
> parameters of O: internal media scattering & absorption and light
> attenuation of O (fade_distance, fade_power).

  For the position of the light source on the ray, I think we should do
some optics (heh, we're speaking about a raytracer, are we not?).  Take
into consideration the curvatures of the surface at the entry and exit
point of the ray into and out of the object.  Like for lenses, you know.
But, this would require not only to calculate normals (for the tangent
plan) but also these curvatures.  Not sure whether POV knows how to do it
in a general case.  Maybe some approximations (by sampling again) would be
necessary...

  I wish I had some more time.

Roland.
-- 
Les francophones m'appellent Roland Mas,
English speakers call me Rowlannd' Mass,
Nihongode hanasu hitoha [Lolando Masu] to iimasu.
Choisissez ! Take your pick ! Erande kudasai !

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