clipka <ano### [at] anonymousorg> wrote:
> Am 02.09.2015 um 20:59 schrieb Cousin Ricky:
> > On 2015-09-02 09:49 AM (-4), clipka wrote:
> >> I would recommend using a non-zero fade_distance, set to be equal to the
> >> corresponding object's radius. That more closely mimicks the
> >> characteristics of a non-point light source.
> >
> > Is this true even for area_illumination with circular orient?
>
> Hum - that's a good question I've never thought about. But by extension
> of what I said, if you model a single non-point light source as an array
> of smaller light sources, then those smaller light sources'
> fade_distance should be set equal to their radius, so for a highly
> subdivided area_illumination light source the fade_distance should
> indeed probably be close to zero.

One complication is that points near the center of the grid are in the same
plane as points on the edge of the grid, which should not be the case for a
spherical extended light source.

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"Cousin Ricky" <rickysttATyahooDOTcom> wrote:
> clipka <ano### [at] anonymousorg> wrote:
> > Am 02.09.2015 um 20:59 schrieb Cousin Ricky:
> > > On 2015-09-02 09:49 AM (-4), clipka wrote:
> > >> I would recommend using a non-zero fade_distance, set to be equal to the
> > >> corresponding object's radius. That more closely mimicks the
> > >> characteristics of a non-point light source.
> > >
> > > Is this true even for area_illumination with circular orient?
> >
> > Hum - that's a good question I've never thought about. But by extension
> > of what I said, if you model a single non-point light source as an array
> > of smaller light sources, then those smaller light sources'
> > fade_distance should be set equal to their radius, so for a highly
> > subdivided area_illumination light source the fade_distance should
> > indeed probably be close to zero.
>
> One complication is that points near the center of the grid are in the same
> plane as points on the edge of the grid, which should not be the case for a
> spherical extended light source.

For a common lambertian emission surface, every small area on the plane emit
light that obeys the cosine law. Obeying it give the emission along the normal
line maximum, and along the surface minimum(in fact zero).
https://en.wikipedia.org/wiki/Lambert%27s_cosine_law

It can still be simulated by an array of light_source, but each light_source
must be the case that emit light compliant the cosine law intensity.
In POV-Ray we can achieve this by using the spotlight and radius 90 falloff 90 ,
tightness 1.

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> Am 02.09.2015 um 20:59 schrieb Cousin Ricky:
>> On 2015-09-02 09:49 AM (-4), clipka wrote:
>>> I would recommend using a non-zero fade_distance, set to be equal to the
>>> corresponding object's radius. That more closely mimicks the
>>> characteristics of a non-point light source.
>>
>> Is this true even for area_illumination with circular orient?
>
> Hum - that's a good question I've never thought about. But by extension
> of what I said, if you model a single non-point light source as an array
> of smaller light sources, then those smaller light sources'
> fade_distance should be set equal to their radius, so for a highly
> subdivided area_illumination light source the fade_distance should
> indeed probably be close to zero.
>

But, if I remember the documentation correctly, setting fade_distance to 
zero effectively turn light fading off.

So, a very small, but non-zero, value is required.

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Am 09.09.2015 um 00:53 schrieb Alain:

>> Am 02.09.2015 um 20:59 schrieb Cousin Ricky:
>>> On 2015-09-02 09:49 AM (-4), clipka wrote:
>>>> I would recommend using a non-zero fade_distance, set to be equal to
>>>> the
>>>> corresponding object's radius. That more closely mimicks the
>>>> characteristics of a non-point light source.
>>>
>>> Is this true even for area_illumination with circular orient?
>>
>> Hum - that's a good question I've never thought about. But by extension
>> of what I said, if you model a single non-point light source as an array
>> of smaller light sources, then those smaller light sources'
>> fade_distance should be set equal to their radius, so for a highly
>> subdivided area_illumination light source the fade_distance should
>> indeed probably be close to zero.
> 
> But, if I remember the documentation correctly, setting fade_distance to
> zero effectively turn light fading off.
> 
> So, a very small, but non-zero, value is required.

That used to be the case indeed. As of POV-Ray 3.7.1, however,
fade_distance can be set to 0 for effect: The distance-based fading will
then follow a true inverse power law (effective_brightness =
nominal_brightness / (distance^fade_power)) rather than POV-Ray's
traditional fading formula; nominal brightness will be achieved at unit
distance.

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On Wed, 09 Sep 2015 01:54:54 +0200, clipka <ano### [at] anonymousorg> wrote:


> That used to be the case indeed. As of POV-Ray 3.7.1, however,
> fade_distance can be set to 0 for effect: The distance-based fading will
> then follow a true inverse power law (effective_brightness =
> nominal_brightness / (distance^fade_power)) rather than POV-Ray's
> traditional fading formula; nominal brightness will be achieved at unit
> distance.
>

Maybe I'm getting something wrong, but this looks like divide by zero to  
me.

-- 
-Nekar Xenos-

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Am 09.09.2015 um 04:31 schrieb Nekar Xenos:
> On Wed, 09 Sep 2015 01:54:54 +0200, clipka <ano### [at] anonymousorg> wrote:
> 
> 
>> That used to be the case indeed. As of POV-Ray 3.7.1, however,
>> fade_distance can be set to 0 for effect: The distance-based fading will
>> then follow a true inverse power law (effective_brightness =
>> nominal_brightness / (distance^fade_power)) rather than POV-Ray's
>> traditional fading formula; nominal brightness will be achieved at unit
>> distance.
>>
> 
> Maybe I'm getting something wrong, but this looks like divide by zero to
> me.

At a distance of zero - yes. But if you place a light source at a
distance of zero to a surface, you have other problems anyway.

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On Wed, 09 Sep 2015 11:31:13 +0200, clipka <ano### [at] anonymousorg> wrote:

> Am 09.09.2015 um 04:31 schrieb Nekar Xenos:
>> On Wed, 09 Sep 2015 01:54:54 +0200, clipka <ano### [at] anonymousorg>  
>> wrote:
>>
>>
>>> That used to be the case indeed. As of POV-Ray 3.7.1, however,
>>> fade_distance can be set to 0 for effect: The distance-based fading  
>>> will
>>> then follow a true inverse power law (effective_brightness =
>>> nominal_brightness / (distance^fade_power)) rather than POV-Ray's
>>> traditional fading formula; nominal brightness will be achieved at unit
>>> distance.
>>>
>>
>> Maybe I'm getting something wrong, but this looks like divide by zero to
>> me.
>
> At a distance of zero - yes. But if you place a light source at a
> distance of zero to a surface, you have other problems anyway.
>

I was tired when I posted. I seem to have read "fade_distance" and  
"distance^fade_power" as the same thing.

I heard somewhere that lack of sleep can be similar to having a couple of  
glasses of wine...

-- 
-Nekar Xenos-

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On 9/9/2015 8:00 PM, Nekar Xenos wrote:
> I heard somewhere that lack of sleep can be similar to having a couple
> of glasses of wine...

A couple of buckets, more likely. ;-)

-- 

Regards
     Stephen

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Am 09.09.2015 um 21:00 schrieb Nekar Xenos:

> I heard somewhere that lack of sleep can be similar to having a couple
> of glasses of wine...

Mandatory viewing:

https://youtu.be/zkGVwsJkXt0

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Hi(gh)!

On 09.09.2015 23:28, clipka wrote:

> Mandatory viewing:
>
> https://youtu.be/zkGVwsJkXt0

And now a video on drunk POVing!

Hmmm... perhaps I should try out some Georgian wines from a nearby 
supermarket, get really stoned and then try to program a sophisticated 
scene, while running an ffmpeg screen capture!

See you in Khyberspace!

Yadgar

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