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29 Jul 2024 08:15:38 EDT (-0400)
  light_group and photons (Message 1 to 6 of 6)  
From: James Holsenback
Subject: light_group and photons
Date: 16 Sep 2012 08:55:15
Message: <5055cc33$1@news.povray.org>
Struggling a bit to light my amethyst ring (posted in p.b.images) and 
decided to try a light_group. I have:

union {
   light_group {
     object { Stone material { StoneMaterial } hollow on }
     light_source { Stone_Light }
     #if (UsePhotons)
       photons {target reflection on refraction on collect off }
     #end
     global_lights off
     }
   object { Band material { BandMaterial }
   }

The stone light has reflection/refraction set to on and the scene light 
has them turned off, but I get: Photon Warning: Could not save photon 
map - no photons!

Is this even possible, or am I on a fools errand?


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From: Alain
Subject: Re: light_group and photons
Date: 16 Sep 2012 13:20:44
Message: <50560a6c$1@news.povray.org>

> Struggling a bit to light my amethyst ring (posted in p.b.images) and
> decided to try a light_group. I have:
>
> union {
>    light_group {
>      object { Stone material { StoneMaterial } hollow on }
>      light_source { Stone_Light }
>      #if (UsePhotons)
>        photons {target reflection on refraction on collect off }
>      #end
>      global_lights off
>      }
>    object { Band material { BandMaterial }
>    }
>
> The stone light has reflection/refraction set to on and the scene light
> has them turned off, but I get: Photon Warning: Could not save photon
> map - no photons!
>
> Is this even possible, or am I on a fools errand?

How can you shoot protons to the light_source?
I think that you should put the photons block with the Stone object and 
have none for the actual light_source. The light will use the default 
photons setting where both reflection and refraction are enabled.
By the way, unless your stone contains some media, the hollow attribute 
is useless.


Alain


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From: James Holsenback
Subject: Re: light_group and photons
Date: 17 Sep 2012 07:28:17
Message: <50570951$1@news.povray.org>
On 09/16/2012 01:20 PM, Alain wrote:

>> Struggling a bit to light my amethyst ring (posted in p.b.images) and
>> decided to try a light_group. I have:
>>
>> union {
>>    light_group {
>>      object { Stone material { StoneMaterial } hollow on }
>>      light_source { Stone_Light }
>>      #if (UsePhotons)
>>        photons {target reflection on refraction on collect off }
>>      #end
>>      global_lights off
>>      }
>>    object { Band material { BandMaterial }
>>    }
>>
>> The stone light has reflection/refraction set to on and the scene light
>> has them turned off, but I get: Photon Warning: Could not save photon
>> map - no photons!
>>
>> Is this even possible, or am I on a fools errand?
>
> How can you shoot protons to the light_source?

LOL ... frustrated and snagged wrong example.

> I think that you should put the photons block with the Stone object and
> have none for the actual light_source. The light will use the default
> photons setting where both reflection and refraction are enabled.

Already tried that incantation. Still think photons and light_group is a 
no go. I'll prepare a better example when I get a chance.

> By the way, unless your stone contains some media, the hollow attribute
> is useless.

poseray did that just didn't bother removing it

>
>
> Alain


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From: James Holsenback
Subject: Re: light_group and photons
Date: 17 Sep 2012 12:04:52
Message: <50574a24@news.povray.org>
On 09/17/2012 07:28 AM, James Holsenback wrote:
> Already tried that incantation. Still think photons and light_group is a
> no go. I'll prepare a better example when I get a chance.

OK ... below is a simplified scene used to show the problem I'm having. 
The scene is initially setup with the Key_Light as the photon source and 
/without/ the light_group ... it shows that indeed it does shoot photons 
properly.

Now remove comments from around the light_group code in the Ring 
definition, and in the Key_Light change reflection/refraction from /on/ 
to /off/ (now I want the Stone_Light to be the photon source) and see 
what I mean.

Maybe not related but why does the stone shadow /still/ appear to be 
coming from the Key_Light and /not/ the Stone_Light ... I have 
global_lights set to off in the light_group!

Here's the scene file:
// render using: povray +p +w1120 +h630 Work.pov
#version 3.7;

#default {finish {ambient 0 emission 0 diffuse 0.6}}

#declare PQ = 1;

#if (PQ > 0)
   #declare UsePhotons = yes;
   #declare PhotonRun = yes; // change to "no" to reuse a map
#end

#switch (PQ)
   #case (0)
     #declare UsePhotons = no;
   #break
   #case (1)
     #declare S_val = 0.1;
     #declare T_val = 5;
		#declare C_val = 15000;
   #break
   #case (2)
     #declare S_val = 0.025;
      #declare T_val = 10;
		#declare C_val = 30000;
   #break
   #case (3)
     #declare S_val = 0.00625;
     #declare T_val = 50;
		#declare C_val = 60000;
   #break
#end

global_settings {
	max_trace_level 64
	adc_bailout 0.00001
	noise_generator 3
	assumed_gamma 1.0
	#if(UsePhotons)
		photons {
			spacing S_val
			autostop 1
			max_trace_level T_val
			count C_val
			#if (PhotonRun)
				save_file "Work.ph"
			#else
				load_file "Work.ph"
			#end
			}
	#end
	}

camera {
	perspective
	location <0,0,-10>
	rotate x*35
	rotate y*10
	look_at <0,1,0>
	right  x*4/3
	direction 1*z
	}

#declare Key_Light =
light_source {
	#declare LightColor = srgb 1;
	0, LightColor
	translate <0,0,-15>
	#if (UsePhotons)
		photons { reflection on refraction on }
	#end
	}

// -- The Stone Light ( in a light_group )
#declare Stone_Light =
light_source {
	#declare LightColor = srgb 1;
	0, LightColor
	translate <0,2,5>
	looks_like {sphere {0,0.125 pigment { srgb <1,1,0>}} }
	#if (UsePhotons)
		photons { reflection on refraction on }
	#end
	}

#declare Stone =	
sphere { 0,1
	material{
	texture{
		pigment{
			srgbf <0.4980, 0.2902, 0.4235,1>
			}
		normal { facets coords 1 size 0.25}								
		finish{
			specular 1
       			roughness 0.01
			diffuse 0.6
			reflection{
				srgb <0.4980, 0.2902, 0.4235>*0.1, srgb <0.4980, 0.2902, 
0.4235>*0.125 fresnel on
				}
			}
		}
	interior {
		ior 1.75
		fade_distance 2
		fade_power 1001
		fade_color <0.4980, 0.2902, 0.4235>
		#if (UsePhotons)
			caustics 1.0
			dispersion 1.05
			dispersion_samples 10
		#end
		}
	}
	#if (UsePhotons)
		photons { target reflection on refraction on collect off }
	#end
	}

#declare Band =
torus { 3,0.25
	material{
		texture{
			pigment{
				srgb <0.8100,0.7100,0.2300>
				}
			finish{
				specular 0.8
				roughness 0.1
				diffuse 0.6
				metallic
				brilliance 5
				reflection{srgb <0.8100,0.7100,0.2300>*0.75, srgb 
<0.8100,0.7100,0.2300>}
				}
			}
		}
	}

#declare Ring =
union {
	//light_group {
		object{
			Stone
			#if (UsePhotons)
				photons { target reflection on refraction on collect off }
			#end
			}
		//light_source { Stone_Light }
		//global_lights off
		//}
	object{
		Band
		translate x*3.95
		}
	translate <-3.95/2,2,0>
	}

object { Key_Light rotate x*45 rotate y*30 }
background { srgb 1 }
plane { y,0 pigment { srgb 1 } }
object { Ring }


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From: Alain
Subject: Re: light_group and photons
Date: 20 Sep 2012 01:34:40
Message: <505aaaf0@news.povray.org>

> On 09/17/2012 07:28 AM, James Holsenback wrote:
>> Already tried that incantation. Still think photons and light_group is a
>> no go. I'll prepare a better example when I get a chance.
>
> OK ... below is a simplified scene used to show the problem I'm having.
> The scene is initially setup with the Key_Light as the photon source and
> /without/ the light_group ... it shows that indeed it does shoot photons
> properly.
>
> Now remove comments from around the light_group code in the Ring
> definition, and in the Key_Light change reflection/refraction from /on/
> to /off/ (now I want the Stone_Light to be the photon source) and see
> what I mean.
>
> Maybe not related but why does the stone shadow /still/ appear to be
> coming from the Key_Light and /not/ the Stone_Light ... I have
> global_lights set to off in the light_group!
>

It looks like photons from a light_group are indeed broken. They don't 
even show on an added object added in the light_group placed to receive 
them.

Any object can intercept light from any light and cause shadows. The 
appartenance to a light_group don't change that.
Also, any object outside the light_group can cause shadow on an object 
of a light_group if it's situated between the light and it's associated 
object(s).

The only objects that don't cause shadows are those having an explicite 
no_shadow attribute.
The only light that don't cause any shadow are shadowless ones. They 
also never cause any highlight and, by default, never cast any photons. 
I don't know if you can force a shadowless light to cast photons by 
adding photons{refraction on reflection on}.

Remove caustics 1.0. It's only good at simulating caustics under a body 
of water on a relatively flat and level surface.

There is no reason to remove the photons block in a non-photons scene or 
in a test render without photons. In this case, the photons block will 
simply be ignored.

In the global_settings, you must NOT use both spacing and count in the 
photons block. Use only one OR the other.

autostop 1 is the same as not using autostop.


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From: James Holsenback
Subject: Re: light_group and photons
Date: 20 Sep 2012 08:28:00
Message: <505b0bd0$1@news.povray.org>
On 09/20/2012 01:34 AM, Alain wrote:

>> On 09/17/2012 07:28 AM, James Holsenback wrote:
>>> Already tried that incantation. Still think photons and light_group is a
>>> no go. I'll prepare a better example when I get a chance.
>>
>> OK ... below is a simplified scene used to show the problem I'm having.
>> The scene is initially setup with the Key_Light as the photon source and
>> /without/ the light_group ... it shows that indeed it does shoot photons
>> properly.
>>
>> Now remove comments from around the light_group code in the Ring
>> definition, and in the Key_Light change reflection/refraction from /on/
>> to /off/ (now I want the Stone_Light to be the photon source) and see
>> what I mean.
>>
>> Maybe not related but why does the stone shadow /still/ appear to be
>> coming from the Key_Light and /not/ the Stone_Light ... I have
>> global_lights set to off in the light_group!
>>
>
> It looks like photons from a light_group are indeed broken. They don't
> even show on an added object added in the light_group placed to receive
> them.
 >
> Any object can intercept light from any light and cause shadows. The
> appartenance to a light_group don't change that.
> Also, any object outside the light_group can cause shadow on an object
> of a light_group if it's situated between the light and it's associated
> object(s).
>
> The only objects that don't cause shadows are those having an explicite
> no_shadow attribute.
> The only light that don't cause any shadow are shadowless ones. They
> also never cause any highlight and, by default, never cast any photons.
> I don't know if you can force a shadowless light to cast photons by
> adding photons{refraction on reflection on}.
>
> Remove caustics 1.0. It's only good at simulating caustics under a body
> of water on a relatively flat and level surface.
>
> There is no reason to remove the photons block in a non-photons scene or
> in a test render without photons. In this case, the photons block will
> simply be ignored.
>
> In the global_settings, you must NOT use both spacing and count in the
> photons block. Use only one OR the other.
>
> autostop 1 is the same as not using autostop.

thanks for the sanity check (i'll file a bug report) and the additional 
information is also useful as photons use is one of my weak areas.


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