"Nathan Kopp" <pov### [at] nkoppmailshellcom> wrote:
> Unfortunately, this isn't an ideal scene for photons.  You'll probably end
> up having to set some of the settings manually, specifically the "radius",
> the spacing, and possibly the expand_thresholds.  Normally, POV computes
> these autmomatically.  However, some scenes that have very disparate photon
> densities can confuse these automated algorithms (which are fairly
> primative, I admit).
>
> Some things to try:
>
> 1) Start by greatly increasing the number of photons in your scene.  The
> white dots that you see are individual photons, and each photon is carrying
> a LOT of energy.  For good results, you'll probably need at least ten times
> as many photons.
>

Ok. That's good information. Thanks. I figured that 1,000,000 was probably a
big enough number to use since all the examples I looked at used between
10,000 and 100,000. Also, I watched the count during pre-rendering, and it
stopped shooting photons after about 30,000ish, so I thought that count was
probably high enough. Based on suggestions, I will likely use spacing
rather than count.

> 2) Use the "multiplier" option for the "radius" setting.  Here's an example:
> photons
> {
>   ...
>   radius /*first parameter is optional*/, 5
>   ...
> }
> This will tell POV to take it's auto-guessed gather radius and multiply it
> by five.  If that doesn't smooth out the photons, try multiplying by ten.
>

Ok. It looks like this parameter goes in the photons {} block of the
global_settings? I was starting to get a bit confused about which
parameters to specify in the global_settings and which ones to put in the
individual target blocks, but after reading the pertinent help file a few
more times, it's now starting to make more sense.

> 3) Try specifying the spacing (as opposed to "count") and the exact gather
> radius.  Example:
> photons
> {
>   spacing 0.1
>   radius 0.05
> }
> Note that the proper values for spacing and radius will depend on your scene
> size.  Spacing will be close to the average space between photons deposited
> on the surface.  Note that usually a good radius:spacing ratio is 5:1.
>

I'm assuming this is a typo. Since the ratio needs to be 5:1, then it needs
to be either spacing 0.1; radius 0.5 OR spacing 0.01; radius 0.05. I'm
guessing the latter. It also seems that with the above (#2) comment, my
resulting block should look something like:

photons
{
  spacing 0.01
  radius 0.05, 5
  autostop 0
}

Look right?

> BTW, the "Photons FAQ" section of the documentation specifically addresses
> this problem.

Yes, I have read, and re-read the FAQ, but comments here have helped to
clarify some of my questions. Most importantly, I was under the impression
that count and spacing were interchangeable, in other words, increasing the
count is pretty much the same thing as decreasing the spacing. This doesn't
seem to be the case. I really appreciate the help, and I will let you know
the results of my experiments.

>
> -Nathan
>
>
>
> "dan B hentschel" <dan### [at] alumritedu> wrote...
> > This is the image that pertains to my question on photon usage in
> > povray.newusers. I know. It's pretty ugly. It's obvious I am using photons
> > incredibly wrong. I need some suggestions on how to begin. Please excuse
> my
> > ignorance. Also excuse the extreme low quality of this render.
> >
>
>
> ----------------------------------------------------------------------------
> ----

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