"Christoph Hormann" <chr### [at] gmxde> schreef in bericht
news:3E0F289C.4100D6CD@gmx.de...
> > Yep, and although I did misunderstand your question :) , my question
> > remains: if it's possible to calculate 1600 fixed sample directions, it
> > should also be possible (using the same or a similar algorythm) to
calculate
> > an arbitrary amount of fixed sample directions before the actual
raytracing
> > starts.  That way, you don't have to calculate the sample directions on
the
> > fly, and there wouldn't be an upperlimit of 1600 samples.  Or am I
talking
> > nonsense here?
> No, but generating a good distribution is a slow and difficult thing.  So
> calculating them before every render is no good idea.

hmm, ic..

> Any practical solution will have to supply a precalculated table or a tool
> for calculating it (so the user is more flexible with the maximum count).
>
> > > I don't know a method to generate such a distribution in high quality
that
> > > would be fast enough to be run before every render - if you do feel
free
> > > to implement it.
> > I don't know what a "cos theta density distribution" is, but aren't just
> > random (and not (perfectly) uniform distributed) rays good enough?
> "cos theta density distribution" means the density of the samples is not
> constant but proportional to the cosine of the angle to the normal vector.

You mean there will be less samples directed more or less perpendicular to
the surface than those directed more or less parellel to the surface?  Why
is this needed?

> Whether random rays are 'good enough' is a matter of personal taste of
> course but i don't think anyone would use a completely random sampling if
> available.

I know I would, if it was the only way to have more than 1600 samples...
How about this: for the first 1600 samples, use the precalculated table, but
for the next n samples, use a random direction. :)

> > Oh, and an other question: reading the POV-Ray manual gave me the
impression
> > that the re-use of samples is based on the distance of the previous
sample.
> > As far as I can remember, there's nothing about the surface-normal in
the
> > manual.  But IMHO, the surface normal is more (or equaly) important to
> > decide if samples could be re-used.  Am I wrong?  Or is this maybe
already
> > implemented?
> I'm not sure what you mean but the distribution of the samples depends on
> the scene geometry (or the surface normal if you want so).  There is a
> switch in the POV source you can make the sample positions visible with so
> you can see this.  If this is not what you mean please clarify what you
> mean by 'basing the reuse of samples on something'.
I think I'll just assume that the way POV-Ray samples is as good as can be
:)  I'm afraid my English isn't good enough to explain better what I was
trying to say :-/ but I think, if I understand you correctly, things are the
way I think they should be :)

cu!
--
ZK AKA SaD
http://www.povplace.be.tf
"I'm not expendable, I'm not stupid and I'm not going."

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