POV-Ray : Newsgroups : povray.newusers : Possible Photon Error Server Time
28 Mar 2024 15:58:32 EDT (-0400)
  Possible Photon Error (Message 1 to 4 of 4)  
From: kurtz le pirate
Subject: Possible Photon Error
Date: 2 Sep 2014 05:04:56
Message: <54058838$1@news.povray.org>
hello,

i have an issue using photons on one scene.

i get this error :
	"Possible Photon Error: Photon map for media is empty."



excerpts from the source :

#declare usePhotons = true;
...
...
global_settings {
	assumed_gamma 1.80
	max_trace_level 32
	#if (usePhotons)
		photons {
			#if (file_exists(photonFile))
				load_file photonFile
			#else
      			count 1000000
      			autostop 0
    	  		jitter 0.20
			save_file photonFile
			#end
			}
	#end
	}
...
...
light_source {
	p2r(30, 50, 1000,false)
	color White //Wheat // White
	#if (usePhotons)
	   photons {
			refraction on
			reflection on
			}
	#end
	}
...
...
	sphere {
		<0, rSphere, 0>, rSphere
		translate <xIndex,0,zIndex>*2*rSphere
		translate index*deltaY*y
		translate index*<1,0,1>*rSphere
		material { materialVerre }
		#if (usePhotons)
			photons {
				target
				refraction on
				reflection on
				collect off
				}
		#end
		}



who can help me find my error ?
thanks


---
Kurtz le pirate
Compagnie de la Banquise


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From: clipka
Subject: Re: Possible Photon Error
Date: 2 Sep 2014 06:18:53
Message: <5405998d@news.povray.org>
Am 02.09.2014 11:04, schrieb kurtz le pirate:
>
> hello,
>
> i have an issue using photons on one scene.
>
> i get this error :
>      "Possible Photon Error: Photon map for media is empty."

It's only a "possible" error. IIRC it means that you have some interior 
media (probably in "materialVerre") and POV-Ray for some reason thinks 
you would want caustics to show within the media, but finds that after 
photon shooting no photons have hit the media.


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From: Alain
Subject: Re: Possible Photon Error
Date: 3 Sep 2014 15:30:32
Message: <54076c58@news.povray.org>

>
> hello,
>
> i have an issue using photons on one scene.
>
> i get this error :
>      "Possible Photon Error: Photon map for media is empty."
>
>
>
> excerpts from the source :
>
> #declare usePhotons = true;
> ...
> ...
> global_settings {
>      assumed_gamma 1.80
>      max_trace_level 32
>      #if (usePhotons)
>          photons {
>              #if (file_exists(photonFile))
>                  load_file photonFile
>              #else
>                   count 1000000
>                   autostop 0
>                   jitter 0.20
>              save_file photonFile
>              #end
>              }
>      #end
>      }
> ...
> ...
> light_source {
>      p2r(30, 50, 1000,false)
>      color White //Wheat // White
>      #if (usePhotons)
>         photons {
>              refraction on
>              reflection on
>              }
>      #end
>      }
> ...
> ...
>      sphere {
>          <0, rSphere, 0>, rSphere
>          translate <xIndex,0,zIndex>*2*rSphere
>          translate index*deltaY*y
>          translate index*<1,0,1>*rSphere
>          material { materialVerre }
>          #if (usePhotons)
>              photons {
>                  target
>                  refraction on
>                  reflection on
>                  collect off
>                  }
>          #end
>          }
>
>
>
> who can help me find my error ?
> thanks
>
>
> ---
> Kurtz le pirate
> Compagnie de la Banquise

I've found that this message can show when you save photons for later 
use and there is NO media in the scene. In my case, there was fog but no 
proper media.
I suspect that it can also appen if there is no media and no fog.



A little hint:
You don't need to add any photon block to your light_source unless you 
want to use photons{ area_light }.
The default photons block for all light_source, except shadowless, is:
photons{ reflection on refraction on area_light off}

Also, having a photons block when photons is not activated in the 
global_settings block don't have any effect. So, the
#if (usePhotons)...#end have no real use outside of the 
global_settings{...} block.



Alain


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From: kurtz le pirate
Subject: Re: Possible Photon Error
Date: 6 Sep 2014 11:49:52
Message: <540b2d20$1@news.povray.org>

>
> hello,
>
> i have an issue using photons on one scene.
>
> i get this error :
>      "Possible Photon Error: Photon map for media is empty."
 > ...
 > ...


clipa, alain, thanks for your light :)


---
Kurtz le pirate
Compagnie de la Banquise


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