On 1/3/26 13:41, Alain Martel wrote:
> When you use count, the count value is the total number of photons to be 
> shot, distributed between all targets and all lights. The area, or 
> angular size, of the targets also play a role. A big target will tend to 
> get more photons than a small target next to it.
> 
> The photon shooting always try to keep the photon density constant 
> between all targets.
> 
> count 1 000 000
> two lights and two targets of roughly the same size, and each light will 
> shoot about 250 000 photons at each target.
> 
> Have three targets, and you shoot about 166 666 photons per light at 
> each target.

Thank you, Alain. More I didn't know! :-)

Bill P.

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William F Pokorny <ano### [at] anonymousorg> wrote:
> On 1/2/26 20:44, Kenneth wrote:
> >
> > However: Given two (or more) 'target' objects in a scene, the photon behavior
> > for each can be unexpectedly different, depending on whether 'count' vs.
> > 'spacing' is used:
> >
> > A) With 'count':
> > [snip]
> >
> > B) With 'spacing':
> > [snip]

>
> Re: (A) Interesting & news to me. I thought the count applied
> independently to each target. Thanks for digging into the behavior!
>

It was also a new discovery for me...as were Alain's comments when using
*multiple* lights and photon targets. In most of my old photon scenes, I used
'count' out of simplicity-- totally unaware of its various 'if/then/else'
results.

I'm beginning to think that 'count' should be deprecated going forward(!), since
'spacing' easily produces **expected** results, especially with the useful
numerical multiplier for a 'target'.

-------------
BTW (and a bit off-topic):
Just out of curiosity, I tried adding the typical no_shadow and no_image flags
to my photon 'target' object, to see what would happen...and either flag
*eliminated* the caustics on my 'collector' object's surface (in both v3.7 and
3.8). That does not *seem* to be an expected result to me-- based on what those
flags are usually supposed to do-- but I'm still trying to wrap my brain around
the logic it. IF those flags are operating correctly in this case, are photons
'shadow-based' in some way? That is, should photon caustics be regarded as
light/SHADOW effects?

But what definitely seems strange is that adding no_shadow to my *collector*
object eliminated the caustics too.  My understanding of
no_shadow is that it's only supposed to eliminate shadows that are cast *from*
an object (my collector in this case) onto other objects.

Whether or not this is the designed/expected behavior of the two flags when
photons are used, the practical result is that those objects will exhibit
unexpected absence-of-photon effects in a scene (given that 'collect ON' is the
default for all objects when a global photons block is present).  And the use of
no_shadow and no_image for scene 'workarounds' will not work without eliminating
the caustics as well.

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Le 2026-01-05 à 09:46, Kenneth a écrit :
> William F Pokorny <ano### [at] anonymousorg> wrote:
>> On 1/2/26 20:44, Kenneth wrote:
>>>
>>> However: Given two (or more) 'target' objects in a scene, the photon behavior
>>> for each can be unexpectedly different, depending on whether 'count' vs.
>>> 'spacing' is used:
>>>
>>> A) With 'count':
>>> [snip]
>>>
>>> B) With 'spacing':
>>> [snip]
> 
>>
>> Re: (A) Interesting & news to me. I thought the count applied
>> independently to each target. Thanks for digging into the behavior!
>>
> 
> It was also a new discovery for me...as were Alain's comments when using
> *multiple* lights and photon targets. In most of my old photon scenes, I used
> 'count' out of simplicity-- totally unaware of its various 'if/then/else'
> results.
> 
> I'm beginning to think that 'count' should be deprecated going forward(!), since
> 'spacing' easily produces **expected** results, especially with the useful
> numerical multiplier for a 'target'.
> 
> -------------
> BTW (and a bit off-topic):
> Just out of curiosity, I tried adding the typical no_shadow and no_image flags
> to my photon 'target' object, to see what would happen...and either flag
> *eliminated* the caustics on my 'collector' object's surface (in both v3.7 and
> 3.8). That does not *seem* to be an expected result to me-- based on what those
> flags are usually supposed to do-- but I'm still trying to wrap my brain around
> the logic it. IF those flags are operating correctly in this case, are photons
> 'shadow-based' in some way? That is, should photon caustics be regarded as
> light/SHADOW effects?
> 
> But what definitely seems strange is that adding no_shadow to my *collector*
> object eliminated the caustics too.  My understanding of
> no_shadow is that it's only supposed to eliminate shadows that are cast *from*
> an object (my collector in this case) onto other objects.
> 
> Whether or not this is the designed/expected behavior of the two flags when
> photons are used, the practical result is that those objects will exhibit
> unexpected absence-of-photon effects in a scene (given that 'collect ON' is the
> default for all objects when a global photons block is present).  And the use of
> no_shadow and no_image for scene 'workarounds' will not work without eliminating
> the caustics as well.
> 
> 
> 
> 
Then, we must remember that shadowless lights never case photons.

 From your test, it seems that disabling shadows also disable photons.

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On 2026-01-05 10:46, Kenneth wrote:
> 
> It was also a new discovery for me...as were Alain's comments when using
> *multiple* lights and photon targets. In most of my old photon scenes, I used
> 'count' out of simplicity-- totally unaware of its various 'if/then/else'
> results.
> 
> I'm beginning to think that 'count' should be deprecated going forward(!), since
> 'spacing' easily produces **expected** results, especially with the useful
> numerical multiplier for a 'target'.

The last time I used 'count' was around 20 years ago, back when I was
using a 1996 vintage laptop.  When I bought a new laptop in 2006, I
found new freedom with lots of RAM, and have been using only 'spacing'
for new scenes ever since.

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