hi,

"Kenneth" <kdw### [at] gmailcom> wrote:
> "jr" <cre### [at] gmailcom> wrote:
> > > > Kenneth wrote:]
> > > > Would these be more appropriate for the docs' default?:
> > > > target 1.0     When 'spacing' is used in the global photons block
> > > > target on     When 'count' is used in the global photons block
> >
> > why 'on' ??
> > (do you actually want to add further "ambiguities" to the parsing ?
>
> Sorry to say that I did not do much testing of 'target' behavior until now-- and
> it is also a bit confusing to me.
>
> Given that the docs say that the default for an object is 'target 1.0'-- which
> should mean ON as I understand it (when *either* 'count' or 'spacing' is used ...

"The keyword target makes this object a target."  note, keyword alone.
<wiki.povray.org/content/Reference:Photons#Photon_Global_Settings>

as I wrote, the syntax diagram says 'target [float]', a value of '1.0' simply
ensures (I think) that "nothing changes" by default wrt photon spacing.


> ...
> So it seems that the target default is OFF for an object-- unless I am
> completely mistaken as the what 'default of target 1.0' means in the docs (other
> than as an explicit 'spacing divisor').

there isn't a photons "default" either w/out corresponding block, iiuc.  unsure
how 'collect' plays with 'target', but, again aiui, 'refraction' and
'reflection' do not require the object to be a target.

also, fwiw, the documentation calls it a "spacing multiplier", rather than
"divisor".  luckily, with '1.0', no difference :-).


regards, jr.

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"jr" <cre### [at] gmailcom> wrote:

>
> "The keyword target makes this object a target."  note, keyword alone.
> <wiki.povray.org/content/Reference:Photons#Photon_Global_Settings>

You're right about that. Although-- at the risk of sounding pedantic-- the
'default' block in the docs does not actually state it in an immediately useful
way. Instead, the only given default for target is 'target 1.0'.  In my ideal
world, I wish it was clearer:

target: OFF when no explicit target keyword is specified
target spacing: 1.0
>
> as I wrote, the syntax diagram says 'target [float]', a value of '1.0' simply
> ensures (I think) that "nothing changes" by default wrt photon spacing.

Yes, that's my understanding as well, and tests confirm it.

>  but, again aiui, 'refraction' and
> 'reflection' do not require the object to be a target.

Actually, an explicit 'target' *is* required (if my tests are any indication.)
In my test code earlier, in the photon blocks, use 'refraction on' in both the
light_source and the translucent box. Then comment-out 'target' in the
translucent box. The result: no refraction effects.
>
> also, fwiw, the documentation calls it a "spacing multiplier", rather than
> "divisor".  luckily, with '1.0', no difference :-).
>

Ah, yes, you're correct. I was thinking in terms of 'number' of photons rather
than spacing:

target 0.5-- the spacing between photons is reduced by half...whereas the number
of photons is...either doubled or quadrupled(?)-- like spacing/2
(or spacing/4 ?)

Sorry for the confusion.

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I had a window of time today, and set The AI to work on this.

I have diagrams and charts and flowcharts and code.

Still need to go through it all and test it out.
I can post or forward the zips if you'd like.

- BE

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"Kenneth" <kdw### [at] gmailcom> wrote:
>
> I was thinking in terms of 'number' of photons rather
> than spacing:
>
> target 0.5-- the spacing between photons is reduced by half...whereas the number
> of photons is...either doubled or quadrupled(?)-- like spacing/2
> (or spacing/4 ?)
>

"...like spacing/2 or spacing/4" ???

Please ignore that bad analogy and arithmetic-- a result of 'over-thinking' :-[

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hi,

"Kenneth" <kdw### [at] gmailcom> wrote:
> "Kenneth" <kdw### [at] gmailcom> wrote:
> > I was thinking in terms of 'number' of photons rather
> > than spacing:
> > target 0.5-- the spacing between photons is reduced by half...whereas the number
> > of photons is...either doubled or quadrupled(?)-- like spacing/2
> > (or spacing/4 ?)
>
> "...like spacing/2 or spacing/4" ???
> Please ignore that bad analogy and arithmetic-- a result of 'over-thinking' :-[

no worries (hope that sort of thing doesn't keep you awake at night </grin>).

agree re the 'target', its description, will do that in the coming days.  how do
you fancy "having a go" at turning the "Perfect Mirror" thread in to a "FAQ"
item ?  (or a draft for an added "Tip" based on your observations ?)


regards, jr.

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hi,

"Bald Eagle" <cre### [at] netscapenet> wrote:
> I had a window of time today, and set The AI to work on this.
>
> I have diagrams and charts and flowcharts and code.
>
> Still need to go through it all and test it out.
> I can post or forward the zips if you'd like.

keep "us" in the loop please, wrt testing etc.


regards, jr.

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"jr" <cre### [at] gmailcom> wrote:

> keep "us" in the loop please, wrt testing etc.

I have a lot of running around to do, so I'll only be able to sporadically play
with the output.

I'll post a zip of all the files that were generated, and maybe we can all
run/edit/debug the code, etc. and come up with something that makes sense.

One thing that I did was have it generate ALL the possible permutations of light
source and object, and I would suggest that part of the distribution be a scene
that renders all the permutations.  That ought to put an end to any questions
about how povray actually operates.

- BE

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Attachments:
Download 'photons.zip' (1058 KB)

hi,

"Bald Eagle" <cre### [at] netscapenet> wrote:
> ...
> One thing that I did was have it generate ALL the possible permutations of light
> source and object, and I would suggest that part of the distribution be a scene
> that renders all the permutations.  That ought to put an end to any questions
> about how povray actually operates.

yes agree, a simple, "good" .pov/.ini combo which generates a corresponding set
of images would be very useful to have.  (if we had one "in hand", we could
start "badgering" Chris :-))


regards, jr.

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"jr" <cre### [at] gmailcom> wrote:
>
> How do you fancy "having a go" at turning the "Perfect Mirror" thread into
> a "FAQ" item ?  (or a draft for an added "Tip" based on your observations ?)
>

12/18/25

Sorry for the delay in responding...real-life and holiday chores took over.

Perhaps a combination of FAQ and B.E.'s all-inclusive test-scene idea would be
the best approach to a better understanding of the current photons behavior; I
will try to put together a draft FAQ (or addition to 'photon tips and tricks')
after the New Year...once I get a clear scenario in my head of how best to
approach it.

Meanwhile, I continued testing in v3.8 beta 1-- and came across some
*really* odd behavior of photons interacting with objects (which proved to be
TEMPORARY, I am happy to say.)

Essentially, the parse time for my earlier test scene here wildly increased-- by
about 15X-- when I simply added an additional box object to the scene, on the
left side of my  light_source, and with no photons block in that object (thus
as a photon 'collector', the default behavior.) But such a gigantic parse-time
increase  made no sense whatsoever, and  I spent the better part of *three days*
trying to understand why it was occurring and how to eliminate it, running test
after test. (Adding a photon block with 'collect OFF' solved it..but that should
not have made such a big difference.)

Near the end of this testing process, I decided to shut down v3.8 and run the
scene in v3.7 instead, to compare results: NO odd behavior there, which was a
good sign. So I brought it back to 3.8... and the problem had suddenly
DISAPPEARED! I could not even reproduce it by fiddling with photon settings.

(At some point prior to my v3.7 test, I *might* have shut down my computer--
which I do on occasion, when I know I will be away from it for hours..but I
don't remember if or when.)  So did shutting it down 'fix' something in the
Windows registry? And/or did running 3.7 correct some temporary glitch in the
3.8 code? Or did Microsoft sneak-in a 'silent' Windows update while I wasn't
looking, breaking (OR fixing) something?

Or was it just 'gremlins and goblins' playing with me?? I think that's the
likely answer.  :-o

So my new and painfully-learned philosophy concerning the current 3.8 betas (1,
and most likely 2 as well) is this:

When unexpected  and unexplainable scene behavior suddenly occurs that makes no
sense, first RESTART the computer (or just POV-ray?) and test again!

Now that all is well, I continue testing photons...   :-)

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hi,

"Kenneth" <kdw### [at] gmailcom> wrote:
> "jr" <cre### [at] gmailcom> wrote:
> > How do you fancy "having a go" at turning the "Perfect Mirror" thread into
> > a "FAQ" item ?  (or a draft for an added "Tip" based on your observations ?)
>
> Sorry for the delay in responding...real-life and holiday chores took over.
> Perhaps a combination of FAQ and B.E.'s all-inclusive test-scene idea would be
> the best approach to a better understanding of the current photons behavior; I
> will try to put together a draft FAQ (or addition to 'photon tips and tricks')
> after the New Year...once I get a clear scenario in my head of how best to
> approach it.

thank you very much.  on "second thought" :-), or perhaps as a wiki "How To"
item ?  (more "elbow room")


> Meanwhile, I continued testing in v3.8 beta 1-- and came across some
> *really* odd behavior of photons interacting with objects (which proved to be
> TEMPORARY, I am happy to say.)
> ...
> Near the end of this testing process, I decided to shut down v3.8 and run the
> scene in v3.7 instead, to compare results: NO odd behavior there, which was a
> good sign. So I brought it back to 3.8... and the problem had suddenly
> DISAPPEARED! I could not even reproduce it by fiddling with photon settings.
> ...
> Or was it just 'gremlins and goblins' playing with me?? I think that's the
> likely answer.  :-o

agree, they (machines) can have "a mind of their own", it seems at times.


regards, jr.

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