I'm sure this is a frequent problem, but I just can't find the information 
in the documentation. I'm rendering this scene with photons and as you can 
see in the attached image the returning rays through the cone are coming 
back as speckles. I've tried some of the photon settings with no success. 
Thanks for any suggestions.

-- Dave

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Attachments:
Download 'Speckles.jpg' (40 KB)

Preview of image 'Speckles.jpg'

I ran it again without photons, so it's just a basic glass cone on a wood 
textured plane. What am I missing here?


"NetDave" <new### [at] netdavecom> wrote in message 
news:46edc6c0@news.povray.org...
> I'm sure this is a frequent problem, but I just can't find the information
> in the documentation. I'm rendering this scene with photons and as you can
> see in the attached image the returning rays through the cone are coming
> back as speckles. I've tried some of the photon settings with no success.
> Thanks for any suggestions.
>
> -- Dave

Post a reply to this message

Attachments:
Download 'Specles2.jpg' (27 KB)

Preview of image 'Specles2.jpg'

Increase max_trace_level maybe ?



> I ran it again without photons, so it's just a basic glass cone on a wood 
> textured plane. What am I missing here?
> 
> 
> "NetDave" <new### [at] netdavecom> wrote in message 
> news:46edc6c0@news.povray.org...
>> I'm sure this is a frequent problem, but I just can't find the information
>> in the documentation. I'm rendering this scene with photons and as you can
>> see in the attached image the returning rays through the cone are coming
>> back as speckles. I've tried some of the photon settings with no success.
>> Thanks for any suggestions.
>>
>> -- Dave
> 
> 


-- 
http://sibylone.free.fr

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"NetDave" <new### [at] netdavecom> wrote:
> I ran it again without photons, so it's just a basic glass cone on a wood
> textured plane. What am I missing here?
>
>
> "NetDave" <new### [at] netdavecom> wrote in message
> news:46edc6c0@news.povray.org...
> > I'm sure this is a frequent problem, but I just can't find the information
> > in the documentation. I'm rendering this scene with photons and as you can
> > see in the attached image the returning rays through the cone are coming
> > back as speckles. I've tried some of the photon settings with no success.
> > Thanks for any suggestions.
> >
> > -- Dave

Do they go away if you use high-quality antialiasing?

It might be coincident surfaces causing those artefacts; have you tried
translating the cone upwards (or the plane downwards) by a very small
amount?

Otherwise, as JC suggested, try increasing your max_trace_level.


- sooperFoX

Post a reply to this message

NetDave nous apporta ses lumieres en ce 2007/09/16 20:13:
> I'm sure this is a frequent problem, but I just can't find the information 
> in the documentation. I'm rendering this scene with photons and as you can 
> see in the attached image the returning rays through the cone are coming 
> back as speckles. I've tried some of the photon settings with no success. 
> Thanks for any suggestions.
> 
> -- Dave 
> 
> 
> 
It can be a coincident surface problem: move the cone very slightly up.
It can be not enough photons: reduce the spacing or increace count.
It can be that you exeeded max_trace_level: increase max_trace_level in 
global_settings.

-- 
Alain
-------------------------------------------------
You know you've been raytracing too long when you can describe in perfect, 
legal, pov syntax, how to re-create everything in your computer room using 
primitives and csg operations.
fish-head

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Thanks for all the suggestions everyone. So far nothing has worked. I tried 
a bunch of other objects and they all seem to work ok. I guess I'll come 
back to this sometime, but for now the cone doesn't seem to want to 
cooperate. Lots of other shapes will make this scene work and I'll post it 
when I'm satisfied with the composition.

-- Dave

"NetDave" <new### [at] netdavecom> wrote in message 
news:46edc6c0@news.povray.org...
> I'm sure this is a frequent problem, but I just can't find the information 
> in the documentation. I'm rendering this scene with photons and as you can 
> see in the attached image the returning rays through the cone are coming 
> back as speckles. I've tried some of the photon settings with no success. 
> Thanks for any suggestions.
>
> -- Dave

Post a reply to this message

Hi Dave,

If you're using the area_light keyword *inside* the photons block of your
light_source, that will cause artifacts in a lot of cases. Try disabling it
(you can leave it turned on in your native light_source for the soft
shadows) and you should lose the speckles.

Below is an excerpt from the pov-ray documentation (3.6.3.3 Photons FAQ,
second-last question):

"Photons do work with area lights. However, normally photon mapping ignores
all area light options and treats all light sources as point lights. If you
would like photon mapping to use your area light options, you must specify
the "area_light" keyword within the photons { } block in your light
source's code. Doing this will not increase the number of photons shot by
the light source, but it might cause regular patterns to show up in the
rendered caustics (possibly splotchiness)."

The last sentence is of interest, I think.


-- sooperFoX

"NetDave" <new### [at] netdavecom> wrote:
> Thanks for all the suggestions everyone. So far nothing has worked. I tried
> a bunch of other objects and they all seem to work ok. I guess I'll come
> back to this sometime, but for now the cone doesn't seem to want to
> cooperate. Lots of other shapes will make this scene work and I'll post it
> when I'm satisfied with the composition.
>
> -- Dave
>
> "NetDave" <new### [at] netdavecom> wrote in message
> news:46edc6c0@news.povray.org...
> > I'm sure this is a frequent problem, but I just can't find the information
> > in the documentation. I'm rendering this scene with photons and as you can
> > see in the attached image the returning rays through the cone are coming
> > back as speckles. I've tried some of the photon settings with no success.
> > Thanks for any suggestions.
> >
> > -- Dave

Post a reply to this message

Thanks for the suggestion sooperFoX, but I'm not using area_light at all. 
Here's my light_source:

light_source
{
  <500,350,-100>
  color Light_Color
  spotlight
  radius 1
  falloff 2.5
  tightness 10
  point_at <0, 0, 15>
  photons
  {
    reflection on
    refraction on
  }
}

The wierd thing is this ONLY happens when I use a cone object. Nothing else 
causes it. FWIW, I've attached the final result of my tinkering. Some of the 
old-timers may recognize this from some previous experiments with photons. I 
just resurrected it in order to generate a 1920x1200 version for my new 
monitor desktop.

-- Dave

"sooperFoX" <bon### [at] gmailcom> wrote in message 
news:web.4700aae86a7782f5943b35b60@news.povray.org...
> Hi Dave,
>
> If you're using the area_light keyword *inside* the photons block of your
> light_source, that will cause artifacts in a lot of cases. Try disabling 
> it
> (you can leave it turned on in your native light_source for the soft
> shadows) and you should lose the speckles.
>
> Below is an excerpt from the pov-ray documentation (3.6.3.3 Photons FAQ,
> second-last question):
>
> "Photons do work with area lights. However, normally photon mapping 
> ignores
> all area light options and treats all light sources as point lights. If 
> you
> would like photon mapping to use your area light options, you must specify
> the "area_light" keyword within the photons { } block in your light
> source's code. Doing this will not increase the number of photons shot by
> the light source, but it might cause regular patterns to show up in the
> rendered caustics (possibly splotchiness)."
>
> The last sentence is of interest, I think.
>
>
> -- sooperFoX
>
> "NetDave" <new### [at] netdavecom> wrote:
>> Thanks for all the suggestions everyone. So far nothing has worked. I 
>> tried
>> a bunch of other objects and they all seem to work ok. I guess I'll come
>> back to this sometime, but for now the cone doesn't seem to want to
>> cooperate. Lots of other shapes will make this scene work and I'll post 
>> it
>> when I'm satisfied with the composition.
>>
>> -- Dave
>>
>> "NetDave" <new### [at] netdavecom> wrote in message
>> news:46edc6c0@news.povray.org...
>> > I'm sure this is a frequent problem, but I just can't find the 
>> > information
>> > in the documentation. I'm rendering this scene with photons and as you 
>> > can
>> > see in the attached image the returning rays through the cone are 
>> > coming
>> > back as speckles. I've tried some of the photon settings with no 
>> > success.
>> > Thanks for any suggestions.
>> >
>> > -- Dave
>
>
>
>

Post a reply to this message

Attachments:
Download 'DesktopChessRing2.jpg' (42 KB)

Preview of image 'DesktopChessRing2.jpg'

What happens if you translate the cone upwards by about half the width of
that ring there? Do you still get the speckles then?

If you'd like to share the source of your speckles cone scene I'd be happy
to play with it to try and see what is doing it (or better, to stop it!)

I would also like to see what happens when increasing the resolution of your
render to include only the cone at about/above 1200x1600 or so... what do
the speckles look like then? Maybe it can give some clue as to what is
happening. I have a reasonably fast dual-core PC, so again, I'd be happy to
try this for you on either POV 3.6/3.7 or MegaPOV 1.21 -- which, by the way,
are you using?


Cheers
-- sooperFoX


"NetDave" <new### [at] netdavecom> wrote:
> Thanks for the suggestion sooperFoX, but I'm not using area_light at all.
> Here's my light_source:
>
> light_source
> {
>   <500,350,-100>
>   color Light_Color
>   spotlight
>   radius 1
>   falloff 2.5
>   tightness 10
>   point_at <0, 0, 15>
>   photons
>   {
>     reflection on
>     refraction on
>   }
> }
>
> The wierd thing is this ONLY happens when I use a cone object. Nothing else
> causes it. FWIW, I've attached the final result of my tinkering. Some of the
> old-timers may recognize this from some previous experiments with photons. I
> just resurrected it in order to generate a 1920x1200 version for my new
> monitor desktop.

Post a reply to this message

I posted  the a sample of the code that demonstrates the problem in 
p.b.scenefiles. I'm using the current POV release. I noticed that if I 
translate the cone a towards the foreground, the speckles seem to diminish, 
but that doesn't solve my question.

"sooperFoX" <bon### [at] gmailcom> wrote in message 
news:web.47206f316a7782f5943b35b60@news.povray.org...
> What happens if you translate the cone upwards by about half the width of
> that ring there? Do you still get the speckles then?
>
> If you'd like to share the source of your speckles cone scene I'd be happy
> to play with it to try and see what is doing it (or better, to stop it!)
>
> I would also like to see what happens when increasing the resolution of 
> your
> render to include only the cone at about/above 1200x1600 or so... what do
> the speckles look like then? Maybe it can give some clue as to what is
> happening. I have a reasonably fast dual-core PC, so again, I'd be happy 
> to
> try this for you on either POV 3.6/3.7 or MegaPOV 1.21 -- which, by the 
> way,
> are you using?
>
>
> Cheers
> -- sooperFoX
>
>
> "NetDave" <new### [at] netdavecom> wrote:
>> Thanks for the suggestion sooperFoX, but I'm not using area_light at all.
>> Here's my light_source:
>>
>> light_source
>> {
>>   <500,350,-100>
>>   color Light_Color
>>   spotlight
>>   radius 1
>>   falloff 2.5
>>   tightness 10
>>   point_at <0, 0, 15>
>>   photons
>>   {
>>     reflection on
>>     refraction on
>>   }
>> }
>>
>> The wierd thing is this ONLY happens when I use a cone object. Nothing 
>> else
>> causes it. FWIW, I've attached the final result of my tinkering. Some of 
>> the
>> old-timers may recognize this from some previous experiments with 
>> photons. I
>> just resurrected it in order to generate a 1920x1200 version for my new
>> monitor desktop.
>

Post a reply to this message