"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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