> Alain<aze### [at] qwertyorg>  wrote:
>> It should not affect the photons, but if your photons do cast caustics
>> on that object, they won't show as the receiving surface is no longer
>> visible in any reflection. A reflective object with no_reflection will
>> reflect it's environment but will itself won't be reflected by other
>> reflective surfaces. It will also not self reflect.
>
> This doesn't appear to agree with the results that I'm getting. The
> "no_reflection" approach did in fact work, although other considerations cause
> me to agree that radiosity is more appropriate.
>
>> You must NOT use both count and spacing for your photons. One OR the
>> other, never both. ...
>
> I can definitely believe I was misusing the photon feature; I'm still a newbie
> with it.

It's common isue, several users tend to use both while only one should 
be used.
There was also the isue of using reflection with a value larger than 1. 
The faint illumination on the moon was amplified 20 times causing an 
overly bright reflection.

>
>> You should make your light_source parallel.
>
> I would rather not, thanks, unless it is producing significant rounding errors
> or slowing down the scene computation.

Using parallel allow you to place the light_source representing a very 
far light much closer.
Usualy, light comming from a sun is such a case. You often end up with a 
light_source situated at over 100 000 000 units or even more when 
atempting to use real world distances, and that WILL cause problems, 
including causing the light_source to vanish.
Our Sun is at around 150000000 Km from us. In a scene scaled in m, the 
range of values is just to large to reliably compute (easily 10e10~10e12 
to 1).

>
>> You should NOT use ambient_lights 0.
>> It beter to always use assumed_gamma 1 for all scenes.
>
> As for ambient_light vs. assumed_gamma, it looks to me like their purposes are
> totally different. An ambient_light of zero is recommended on this documentation
> page for version 3.6:
> http://povray.org/documentation/view/3.6.1/270/
If you set ambient_lights 0 in a radiosity scene, you can't use high 
ambient finish as a source of illumination. Using version 3.7, you can 
use the emission finish component to have glowing objects.

ambient_lights in the global_settings purpose it to colour the ambient 
component.
It's way beter to use

#default{finish{ambient 0}}

or

add finish{ambient 0} in your textures.

assumed_gamma 1 use a linear scale allowing correct colour evaluations.

>
>> You should upgrade to version 3.7. It works much beter.
>
> Upgrading to version 3.7 sounds exciting but unnecessary at this time.

There are significant differences, many bug fixes, new features and tons 
of various improvements.
If you have a multicores processor, it will automaticaly use them all, 
for greatly improved render time. Even using a single core, it's very 
often faster than 3.6.1.
If you ever interupt a radiosity scene with 3.6.1, there will be a 
visible discontinuity. Not so with 3.7.

It's not about an exiting thing, but more about starting with a current 
version and not having to un-learn things that are no longer relevent.

>
>
>

Alain

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