POV-Ray : Newsgroups : povray.binaries.images : Photon problems? Server Time
15 Aug 2024 10:18:50 EDT (-0400)
  Photon problems? (Message 1 to 9 of 9)  
From: earthdog
Subject: Photon problems?
Date: 10 Jul 2002 09:13:10
Message: <3D2C32EC.4060009@NOSPAMevil3d.net>
I've got some strange artifact showing here.  Are photons the problem? 
This is my first attempt at using them, but textures/settings came pat 
from one of the bundled pov scene files.  I tried playing with 
count,jitter and spacing....


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From: TinCanMan
Subject: Re: Photon problems?
Date: 10 Jul 2002 10:21:58
Message: <3d2c4306@news.povray.org>
"earthdog" <ear### [at] NOSPAMevil3dnet> wrote in message
news:3D2### [at] NOSPAMevil3dnet...
> I've got some strange artifact showing here.  Are photons the problem?
> This is my first attempt at using them, but textures/settings came pat
> from one of the bundled pov scene files.  I tried playing with
> count,jitter and spacing....

It would appear to be photon artifacts.
What are your global, lightsource and object photon settings?  Also what is
the scale of the scene in relation to this?

-tgq


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From: earthdog
Subject: Re: Photon problems?
Date: 10 Jul 2002 10:55:21
Message: <3D2C4AD9.3050307@NOSPAMevil3d.net>
TinCanMan wrote:
> "earthdog" <ear### [at] NOSPAMevil3dnet> wrote in message
> news:3D2### [at] NOSPAMevil3dnet...
> 
>>I've got some strange artifact showing here.  Are photons the problem?
>>This is my first attempt at using them, but textures/settings came pat
>>from one of the bundled pov scene files.  I tried playing with
>>count,jitter and spacing....
> 
> 
> It would appear to be photon artifacts.
> What are your global, lightsource and object photon settings?  Also what is
> the scale of the scene in relation to this?
> 
> -tgq
> 
> 

I've posted the source for the scene in povray.text.scene-files.  I 
wouldn't think the scene is scaled abnormally.  The sphere is one 
pov-unit in radius.  The camera is location<-7,6,-4>.  I'm stumped.

-- Jeff


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From: TinCanMan
Subject: Re: Photon problems?
Date: 10 Jul 2002 11:27:24
Message: <3d2c525c@news.povray.org>
> I've posted the source for the scene in povray.text.scene-files.  I
> wouldn't think the scene is scaled abnormally.  The sphere is one
> pov-unit in radius.  The camera is location<-7,6,-4>.  I'm stumped.
>
> -- Jeff
>

Yeah I see that now.  I think it is as ingo said.  The light source is too
close to the object.  The resulting photons get spread out too much to cover
the entire object. In order to get smoother results at this distance you
need to play with the various settings, either increase 'count' or deacrease
'spacing' (use only one of the two as they mutually exclusive, only one is
used if both are specified), also try increasing 'radius'.

-tgq


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From: earthdog
Subject: Re: Photon problems?
Date: 10 Jul 2002 11:43:42
Message: <3D2C5636.9030700@NOSPAMevil3d.net>
TinCanMan wrote:
>>I've posted the source for the scene in povray.text.scene-files.  I
>>wouldn't think the scene is scaled abnormally.  The sphere is one
>>pov-unit in radius.  The camera is location<-7,6,-4>.  I'm stumped.
>>
>>-- Jeff
>>
> 
> 
> Yeah I see that now.  I think it is as ingo said.  The light source is too
> close to the object.  The resulting photons get spread out too much to cover
> the entire object. In order to get smoother results at this distance you
> need to play with the various settings, either increase 'count' or deacrease
> 'spacing' (use only one of the two as they mutually exclusive, only one is
> used if both are specified), also try increasing 'radius'.
> 
> -tgq
> 
> 

Thanks for the help.  As I told Ingo, I used his suggestions and got rid 
of any 'count' reference and decreased my spacing and added a glass 
cylinder.  I may have gone overboard with 'spacing 0.001'.  I took about 
6 minutes to open up this reply window while pov sorts ~18,000,000 
photons -- not to mention other open apps on my desktops.  So far, the 
results look good, using the just released 3.5 final.  Seems very 
stable.  I think if there were a memory leak in the linux version, I'd 
have found it :).


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From: earthdog
Subject: Re: Photon problems?
Date: 10 Jul 2002 11:47:46
Message: <3D2C5729.3050209@NOSPAMevil3d.net>
earthdog wrote:
> TinCanMan wrote:
> 
>>> I've posted the source for the scene in povray.text.scene-files.  I
>>> wouldn't think the scene is scaled abnormally.  The sphere is one
>>> pov-unit in radius.  The camera is location<-7,6,-4>.  I'm stumped.
>>>
>>> -- Jeff
>>>
>>
>>
>> Yeah I see that now.  I think it is as ingo said.  The light source is 
>> too
>> close to the object.  The resulting photons get spread out too much to 
>> cover
>> the entire object. In order to get smoother results at this distance you
>> need to play with the various settings, either increase 'count' or 
>> deacrease
>> 'spacing' (use only one of the two as they mutually exclusive, only 
>> one is
>> used if both are specified), also try increasing 'radius'.
>>
>> -tgq
>>
>>
> 
> Thanks for the help.  As I told Ingo, I used his suggestions and got rid 
> of any 'count' reference and decreased my spacing and added a glass 
> cylinder.  I may have gone overboard with 'spacing 0.001'.  I took about 
> 6 minutes to open up this reply window while pov sorts ~18,000,000 
> photons -- not to mention other open apps on my desktops.  So far, the 
> results look good, using the just released 3.5 final.  Seems very 
> stable.  I think if there were a memory leak in the linux version, I'd 
> have found it :).
> 

Done Tracing
Statistics for ball.pov, Resolution 320 x 240
----------------------------------------------------------------------------
Pixels:           77120   Samples:           92472   Smpls/Pxl: 1.20
Rays:          97612642   Saved:          19447212   Max Level: 25/25
----------------------------------------------------------------------------
Ray->Shape Intersection          Tests       Succeeded  Percentage
----------------------------------------------------------------------------
Cone/Cylinder                 60967976        41877574     68.69
Plane                         78514450        57743972     73.55
Sphere                        54848089        34338253     62.61
Bounding Box                 156629782       121151998     77.35
Light Buffer                   1480185         1235915     83.50
Vista Buffer                    268009          216165     80.66
----------------------------------------------------------------------------
Calls to Noise:                  0   Calls to DNoise:             10
----------------------------------------------------------------------------
Shadow Ray Tests:           370062   Succeeded:               168376
Reflected Rays:           47503012   Total Internal:        10855157
Refracted Rays:           20684856
Transmitted Rays:         15962997
Number of photons shot:       13369305
Surface photons stored:       17603052
Priority queue insert:          640406
Priority queue remove:          106504
Gather function called:         120143
----------------------------------------------------------------------------
Smallest Alloc:                 10 bytes   Largest:           327688
Peak memory used:        352516132 bytes
----------------------------------------------------------------------------
Time For Parse:    0 hours  0 minutes   1.0 seconds (1 seconds)
Time For Photon:   0 hours 32 minutes  25.0 seconds (1945 seconds)
Time For Trace:    0 hours 22 minutes  54.0 seconds (1012 seconds)
     Total Time:    0 hours 49 minutes  18.0 seconds (2958 seconds)


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From: Slime
Subject: Re: Photon problems?
Date: 10 Jul 2002 16:56:05
Message: <3d2c9f65@news.povray.org>
This is interesting! The problem is definitely too low of a count (or too
high of a spacing), since you can actually see individual photons. But I
like how this image shows the distribution of light that a sphere creates
via reflection and refraction.

Still, though, that's strange considering that neither the count nor the
spacing were unreasonable. Perhaps specifying both of them does something
strange internally?

 - Slime
[ http://www.slimeland.com/ ]


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From: earthdog
Subject: Re: Photon problems?
Date: 10 Jul 2002 17:11:53
Message: <3D2CA322.1060109@NOSPAMevil3d.net>
Slime wrote:
> This is interesting! The problem is definitely too low of a count (or too
> high of a spacing), since you can actually see individual photons. But I
> like how this image shows the distribution of light that a sphere creates
> via reflection and refraction.
> 
> Still, though, that's strange considering that neither the count nor the
> spacing were unreasonable. Perhaps specifying both of them does something
> strange internally?
> 
>  - Slime
> [ http://www.slimeland.com/ ]
> 
> 

I'm not at all sure, in answer to your question.  I traced it again with 
(apparently) ridiculously tight spacing and it still came out quite 
grainy.  I guess I'm not holding my mouth quite right when I hit 'Enter'.

-- earthdog


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From: Nathan Kopp
Subject: Re: Photon problems?
Date: 10 Jul 2002 21:21:21
Message: <3d2cdd91@news.povray.org>
Try adding "radius 0,5" to your photons block inside global_settings.  This
will increase the radius used to gather photons by a factor of 5.  For some
reason in your scene, POV incorrectly estimates the gather radius required.
If that still produces grainy results, try "radius 0,10" or even higher.

-Nathan


"earthdog" <ear### [at] NOSPAMevil3dnet> wrote...
> I've got some strange artifact showing here.  Are photons the problem?
> This is my first attempt at using them, but textures/settings came pat
> from one of the bundled pov scene files.  I tried playing with
> count,jitter and spacing....


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