"Johann Uhrmann" <juh### [at] fh-landshutde> wrote in message
news:3d54588c@news.povray.org...
>
> I played around a bit with photons and I wonder why the following picture
> does not contain any (colored) rays from the diamond into the media.
>
> The color dispersion in this images seems to contain just a few colors and
> no smooth color transitions.

Hi there Johann,

Same as 'Raf256', I couldn't see your attached image (maybe that "8-bit"
encoding?). Might have been better to post each part at their respective
places here at the newsgroups, namely image file here, pov file to
povray.text.scene-files (the text in message). Regardless....

....I rendered your script and puzzled over it a while. Found that I could
not get photons in the media other than from the spotlight. When I made a
box to act as media container and room the reflecting photons showed up in
the media, not when only open air media was used.

The photon mapping was working okay showing on the ground, just not in
media, before making that change. I did need to increase the light source
color above one to see it good enough. If the transmit 0.95 is changed to
1.2 that also brightens it up but probably not always okay to do that.

I really wonder about that problem of the missing photons in media if it
isn't enclosed, something either not right or I missed a reason for it. I
won't say it's a bug unless others find likewise.

Now, about that dispersion. Reason that looked sharp-edged for you I guess
is because the default of 7 colors was used, so adding a dispersion_samples
14 would double that.

About that media again. I was surprised to find how the box container
addition slowed it down terribly. I couldn't seem to speed it back up to
it's original render-time, maybe something to do with the previously missing
media photons and now it shows all bouncing around from reflection and
refraction. Still was much, much slower than I'd have expected. So slow in
fact I quit trying to check on it.

Only half helpful perhaps.

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