POV-Ray : Newsgroups : povray.beta-test : Artefacts using +C Server Time
18 Apr 2024 04:30:35 EDT (-0400)
  Artefacts using +C (Message 1 to 10 of 10)  
From: Thomas de Groot
Subject: Artefacts using +C
Date: 18 Sep 2013 10:42:54
Message: <5239bbee$1@news.povray.org>
In a long render, I twice used +C. In each case it seems, a small 
artefact remained from the previous render session (see image in 
p.b.i.). Could this be a bug?

I used:

+w1024 +h576 -a +am2 +bm2 +wt6 +SR288 +EC512 +C

in both cases.

Thomas


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From: Le Forgeron
Subject: Re: Artefacts using +C
Date: 18 Sep 2013 10:55:04
Message: <5239bec8$1@news.povray.org>
Le 18/09/2013 16:42, Thomas de Groot a écrit :
> In a long render, I twice used +C. In each case it seems, a small
> artefact remained from the previous render session (see image in
> p.b.i.). Could this be a bug?
> 
> I used:
> 
> +w1024 +h576 -a +am2 +bm2 +wt6 +SR288 +EC512 +C
> 
> in both cases.
> 
> Thomas

I'm sure the artefact is obvious to you, and will forever be spotted
once you know it, but I fail to see it in the posted image
(which is smaller than 1024 x 576 )

Can you circle it with a red pen ? (sort of)


-- 
Just because nobody complains does not mean all parachutes are perfect.


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From: MichaelJF
Subject: Re: Artefacts using +C
Date: 18 Sep 2013 13:50:01
Message: <web.5239e75b1ca0d3dd126b6c50@news.povray.org>
Le_Forgeron <lef### [at] freefr> wrote:
> Le 18/09/2013 16:42, Thomas de Groot a écrit :
> > In a long render, I twice used +C. In each case it seems, a small
> > artefact remained from the previous render session (see image in
> > p.b.i.). Could this be a bug?
> >
> > I used:
> >
> > +w1024 +h576 -a +am2 +bm2 +wt6 +SR288 +EC512 +C
> >
> > in both cases.
> >
> > Thomas
>
> I'm sure the artefact is obvious to you, and will forever be spotted
> once you know it, but I fail to see it in the posted image
> (which is smaller than 1024 x 576 )
>
> Can you circle it with a red pen ? (sort of)
>
>
> --
> Just because nobody complains does not mean all parachutes are perfect.

Yes I cannot see it too. The last discussion we had about +c issues and
artifacts was due to photon settings and radiosity. Jaime explained and solved
this problem:
http://news.povray.org/povray.binaries.images/thread/%3Cweb.50366087f6191b69535f0ed20%40news.povray.org%3E/?ttop=386863
&toff=200

But here I cannot see a problem. Can it be that I have looked at this cutout
some days ago? It looks very familiar.

Best regards,
Michael


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From: Thomas de Groot
Subject: Re: Artefacts using +C
Date: 19 Sep 2013 03:10:09
Message: <523aa351$1@news.povray.org>
On 18-9-2013 16:55, Le_Forgeron wrote:
> I'm sure the artefact is obvious to you, and will forever be spotted
> once you know it, but I fail to see it in the posted image
> (which is smaller than 1024 x 576 )
>
> Can you circle it with a red pen ? (sort of)

My laziness ;-)  Done.

Thomas


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From: Thomas de Groot
Subject: Re: Artefacts using +C
Date: 19 Sep 2013 03:16:28
Message: <523aa4cc$1@news.povray.org>
On 18-9-2013 19:48, MichaelJF wrote:

> Yes I cannot see it too. The last discussion we had about +c issues and
> artifacts was due to photon settings and radiosity. Jaime explained and solved
> this problem:
>
http://news.povray.org/povray.binaries.images/thread/%3Cweb.50366087f6191b69535f0ed20%40news.povray.org%3E/?ttop=386863
> &toff=200

No. In my view this has nothing to do with radiosity and there are no 
photons in this scene. Jaime's is a different problem.

>
> But here I cannot see a problem. Can it be that I have looked at this cutout
> some days ago? It looks very familiar.

It is part of the Aftermath scene, using focal blur. The artefacts are 
the two little squares (now highlighted) that remain from the pretrace.

Thomas


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From: Thomas de Groot
Subject: Re: Artefacts using +C
Date: 19 Sep 2013 03:29:14
Message: <523aa7ca$1@news.povray.org>
You can see /my/ comment in the following thread:

http://news.povray.org/povray.beta-test/thread/%3Cweb.5033e17517f31266b62e53d00%40news.povray.org%3E/?ttop=386875&toff=50

However, that concerned RC6. The mentioned problem has been solved for 
RC7 but there seems to remain some little glitches.

Thomas


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From: MichaelJF
Subject: Re: Artefacts using +C
Date: 19 Sep 2013 15:10:01
Message: <web.523b4b3b1ca0d3dc5c73f630@news.povray.org>
Thomas de Groot <tho### [at] degrootorg> wrote:
> You can see /my/ comment in the following thread:
>
>
http://news.povray.org/povray.beta-test/thread/%3Cweb.5033e17517f31266b62e53d00%40news.povray.org%3E/?ttop=386875&tof
f=50
>
> However, that concerned RC6. The mentioned problem has been solved for
> RC7 but there seems to remain some little glitches.
>
> Thomas

Hm, seems that this issue is not repaired completely with RC 7. I haven't used
+c much recently, but I can only remember one flaw. In this special case I
overlooked that I had entered another block size within the command line field
and had forgotten to clear the field resuming an other rendering using an
ini-file. Since the Windows version always uses given settings from the
rendering before, I attributed the problem to my fault not erasing the old
Settings, assuming that the ini-file options and the options from the command
line field were added. Unfortunatelly I cannot reproduce this behaviour since I
rerendered the image completely and didn't stored the state-file. And may be my
assumption is wrong.

If you have a smaller area with a long rendering time (may be a diamond) but the
bigger part of the picture is fast, then smaller block sizes can speed up the
total rendering time (slightly).

Best regards,
Michael


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From: MichaelJF
Subject: Re: Artefacts using +C
Date: 29 Sep 2013 03:55:01
Message: <web.5247dc0f1ca0d3d9e9562260@news.povray.org>
"MichaelJF" <mi-### [at] t-onlinede> wrote:
>
> Hm, seems that this issue is not repaired completely with RC 7. I haven't used
> +c much recently, ...

Now I did (see the related thread at p.b.i by Thomas for the image). I see
another problem with radiosity as I had in the past. Now the recalculated
radiosity mosaic overwrites pixels rendered already.


Best regards,
Michael


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From: clipka
Subject: Re: Artefacts using +C
Date: 10 Nov 2013 09:26:15
Message: <527f9787@news.povray.org>
Am 18.09.2013 16:42, schrieb Thomas de Groot:
> In a long render, I twice used +C. In each case it seems, a small
> artefact remained from the previous render session (see image in
> p.b.i.). Could this be a bug?

Sorry for the late response. Can you (or someone else) reproduce the 
problem with some comparatively simple scene?


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From: clipka
Subject: Re: Artefacts using +C
Date: 10 Nov 2013 10:27:51
Message: <527fa5f7$1@news.povray.org>
Am 18.09.2013 16:42, schrieb Thomas de Groot:
> In a long render, I twice used +C. In each case it seems, a small
> artefact remained from the previous render session (see image in
> p.b.i.). Could this be a bug?

I can now confirm that this may happen, that it is a bug, and that it 
actually /is/ radiosity related.

What happens is that the continued render starts the pretrace for the 
missing blocks again; during the early stages of this pretrace, the 
"pixels" may be far larger than the render blocks, and may overpaint 
some already rendered blocks.

I've just coded a hotfix that will prevent pretrace results from being 
written to the image buffer. This way the artifacts will still appear in 
the preview window, but not in the final image file.

Avoiding the artifacts entirely seems a bit tricky, and is probably not 
worth the pain as the pretrace step is scheduled for a redesign anyway.


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