POV-Ray : Newsgroups : povray.newusers : Extinction value of scattering and mirrors Server Time
30 May 2024 11:25:45 EDT (-0400)
  Extinction value of scattering and mirrors (Message 11 to 12 of 12)  
<<< Previous 10 Messages Goto Initial 10 Messages
From: clipka
Subject: Re: Extinction value of scattering and mirrors
Date: 19 Jul 2016 13:08:09
Message: <578e5e79$1@news.povray.org>
Am 19.07.2016 um 17:31 schrieb fsv2712:
> I can decrease spacing to 0.000000001 or increase the count value. But no matter
> how I construct the reflector, it doesn't reflect light if the light source is
> placed at his axis or very near it.
> 
> Furthermore, if I use a plane instead of media the problem remains.
> 
> What draws my attention is that with this geometry for the scene, the number of
> photons shot is always 5 despite the value of spacing or count.

I've just had a look at the potons code, and from what I see it was
designed without paying any thought to the possibility that the light
source could be inside the photon target's bounding sphere (computed as
the sphere that touches all the corners of the bounding box).

It seems to me that the code happens to work for most such cases, but
that's probably more or less coincidental -- and for cases where the
light source happens to be at the center of that bounding sphere, I'm
not at all surprised that the code fails miserably.

One possible workaround would be to create the reflector out of multiple
segments, and making sure that their individual bounding boxes are
centered off the cylinder's axis.


Post a reply to this message

From: fsv2712
Subject: Re: Extinction value of scattering and mirrors
Date: 22 May 2017 13:50:02
Message: <web.59232439f6f56c36bec14beb0@news.povray.org>
Although I have seen your answer with months of delay: Thanks for it.
That explains the behaviour of the program.


Post a reply to this message

<<< Previous 10 Messages Goto Initial 10 Messages

Copyright 2003-2023 Persistence of Vision Raytracer Pty. Ltd.