> On 04/04/2011 07:11 AM, Jim Holsenback wrote:
>> On 04/03/2011 06:55 PM, Alain wrote:

>>>> Am I wrong to expect a light_source that's been included in a
>>>> light_group to interact with scattering media? Also I've noticed in the
>>>> scene stats that it's reporting one less light source when it's
>>>> included
>>>> as part of a light_group ... wuz up wid dat?
>>>
>>> Light from a light_group will only illuminate scattering media that is
>>> part of it's group, BUT, the absorbtion from such media will affect the
>>> light even if it's not in the light_group.
>>
>> ah ... thanks the one thing I didn't try. I didn't see anything in the
>> docs, so I'll double check and make an addition if I come up empty
>> handed.
>>
>
> Didn't see anything, so this section:
> http://wiki.povray.org/content/Documentation:Reference_Section_6.1#Scattering
>
>
> now has a referral (at the bottom) back to the Light Groups section were
> I reworked that section to include the caveat.

There is nothing that say that specificaly, but, we do know that a 
light_source don't illuminate ANYTHING outside of it's group. So, we can 
deduct that it won't illuminate any scattering media that is not 
included in the group.

Likewise, if some object is between the grouped light_source and an 
object from the group, that outside object WILL cast a shadow on the 
object in the group.
 From that, we can deduct that both absorbing media and scattering media 
will also atenuate the light, and cause some shadowing.

Again, the documentation don't mention it explicitely in relation with 
media, but consticency demands it to be that way.



Alain

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