In addition to what Christopher said...

Christoph Hormann wrote:
> I'd suggest you (and everyone else who thinks photons are just like 
> (faked) caustics) to read up how they work before stating such conclusions.

I think I know how photons work and yes, the aim is to produce (in case 
of refractive photons) more accurate caustics. I never claimed that 
"photons are just like (faked) caustics". But the goal is very similar 
in many cases.

> The idea behind making photon settings part of the material certainly is 
> to make it unnecessary for the user to think about which *objects* he 
> wants how many photons for.  But since doing so will not actually change 
> anything in the way POV-Ray distributes the photons this will not result 
> in any actual improvement of the output quality or the render efficiency 
> - it would just create the illusion for the user that he does not need 
> to care about which objects should have photons.

I'm starting to repeat myself, but here goes:

1. The suggestion was to make it easier to alter material 
characteristics. The _result_ of using photons is a material property: 
more realistic caustics and light reflections. Only the calculation 
method differs greatly from other properties and non-visible objects 
have an impact on total render time. I don't understand why this can be 
a reason to make the usage of photons more cumbersome than other 
material properties. Of course there should allways be ways to control 
the amount of time/memory consumed for this calculation.

2. The quality actually might improve as user might omit the usage of 
photons on an object that is not visible whereas reflected of refracted 
photons might still be visible in the field of view - even via 
reflections. The possibility of this happening might be reduced if 
photons were a material property. (And there is no point putting objects 
into scene which don't affect the output in any way...)

3. Why should POV-SDL have "baby-sitting" (no offense meant) features? I 
allways considered it to be quite powerful tool and it is up to user to 
understand what he is doing. It would have been equally odd, if (say, 10 
years ago) you would have been forced to specify refraction for each 
objects individually without having the possibility to inculde it to 
texture declaration: "They take very long to render and you must 
consider every object very carefully..." There are documents that 
explaine the usage of various features and I think users can judge 
themselves how to use them.

> What would really be interesting is a way for POV-Ray to automatically 
> calculate the target values for the objects that receive photons based 
> on their importance for the render result.  There have been various 
> attempts for importance based photon distributions, a good introduction 
> can (although focussed on global photons) be found in:

That would indeed be a good thing. Has any attempts made to implement 
such a thing in Pov-RAY?

Severi

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