POV-Ray : Newsgroups : povray.advanced-users : Is this a bug in 3.6.1c? Server Time
1 Nov 2024 05:20:16 EDT (-0400)
  Is this a bug in 3.6.1c? (Message 1 to 5 of 5)  
From: Jaap Frank
Subject: Is this a bug in 3.6.1c?
Date: 8 Mar 2008 17:43:13
Message: <47d31681$1@news.povray.org>
Hi,

Recently I stumbled over a link to Chris Bartlett's StairCase macro
and downloaded the files.
The first example in StairCaseDoc.pov traced happily in about 7s
with my AMD Athlon 64 3000+ on Windows XP Home SP2.
Because all the examples trace as an animation, I started it with
+kfi0 +kff50 in the command line box and went doing something
else. After a while I checked the progress and noticed that the
tracing was very slow compared to the single trace before.
I quickly checked the messages for the first example and good only
see a difference in the number of objects :
Single trace: 176                Trace time: 7sec
Animation:   168                Trace time: 68sec
Weird, why is there a difference when everything in the file stays the
same?
In order to check every line of the messages I put them beside each
other and found some more differences:

(In the statistics below the first line is the single trace and the second
line is from the animation)

Ray->Shape Intersection       Tests        Succeeded  Percentage
----------------------------------------------------------------
Box                                    506223          120663     23.84
Box                                89402880          221111       0.25
Cone/Cylinder                      21746              3735     17.18
Cone/Cylinder                 25703328             8122       0.03
CSG Intersection                 484477           59250     12.23
CSG Intersection             51406656           76943       0.15
CSG Union                         664369            49209       7.41
CSG Union                     59229408          131033       0.22
Lathe                                  212507            72541     34.14
Lathe                              48054048          155648       0.32
Lathe Bound                       212507          110827     52.15
Lathe Bound                   48054048          195161       0.41
Plane                                  543940          382586     70.34
Plane                                6705216        4650488     69.36
Prism                                1338041          272019     20.33
Prism                              33526080          352735       1.05
Prism Bound                   25342199         2241221      8.84
Prism Bound                  275266864      19341721      7.03
Sphere                                     7470             1798     24.07
Sphere                              4470144              1854       0.04
Clipping Object                   331882          105405     31.76
Clipping Object                   643896          198954     30.90
Bounding Box                   8774139         2655932     30.27
No line !!!
Vista Buffer                      3915348         2326121      59.41
No line !!!

Conclusion: The bounding is off and the Vista Buffers as well.
That explains the statistics and the long trace time.

To be sure I made an ini-file with:

  Bounding=on
  Bounding_Threshold=5
  Draw_Vistas=on
  Light_Buffer=on
  Vista_Buffer=on

in it and traced again. The results don't change, however the
Bounding_Threshold=5  and Draw_Vistas=on were there
in the header, but it didn't work. Vistas in the single trace
works normally.

Can anyone check with some different file if there is something
really wrong with version 3.6.1c.
All my animation files are based on clock values and I never
noticed any differences in trace time with a single trace or in
an animation. However I never used the frame system of POV.
In news.povray.org I can't find any reference to such a behaviour.

I will put the files in povray.binaries.scene-files under
Bug-test-files.

Maybe I do something stupidly wrong, but I don't see it.

Jaap Frank


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From: Chris B
Subject: Re: Is this a bug in 3.6.1c?
Date: 8 Mar 2008 18:41:03
Message: <47d3240f$1@news.povray.org>
"Jaap Frank" <jjf### [at] casemanl> wrote in message 
news:47d31681$1@news.povray.org...
> Hi,
>
> Recently I stumbled over a link to Chris Bartlett's StairCase macro
> and downloaded the files.
> The first example in StairCaseDoc.pov traced happily in about 7s
> with my AMD Athlon 64 3000+ on Windows XP Home SP2.
> Because all the examples trace as an animation, I started it with
> +kfi0 +kff50 in the command line box and went doing something
> else. After a while I checked the progress and noticed that the
> tracing was very slow compared to the single trace before.
> I quickly checked the messages for the first example and good only
> see a difference in the number of objects :
> Single trace: 176                Trace time: 7sec
> Animation:   168                Trace time: 68sec
> Weird, why is there a difference when everything in the file stays the
> same?

The 'StairCaseDoc.pov' file is designed to use the animation feature to 
regenerate all of the 50 different images in the documentation provided with 
the macros. When you use the animation feature with this file, the SDL uses 
the frame number to work out which image to generate, then sets the macro 
parameters for that image. Some of the images contain simple single flights 
of stairs with a small number of objects, others contain multiple flights of 
stairs with a very large number of objects. The render time therefore varies 
a lot from image to image/frame to frame.

> All my animation files are based on clock values and I never
> noticed any differences in trace time with a single trace or in
> an animation. However I never used the frame system of POV.
> In news.povray.org I can't find any reference to such a behaviour.

Even if you just use the clock and don't vary the contents of the scene 
between frames, the render times for different frames can still vary 
depending on the proximity to the camera of different objects. For example, 
a partially transparent or reflective sphere a long way from the camera has 
less impact on render times than if it's close to the camera and generates 
additional rays to trace.

Regards,
Chris B.


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From: Jaap Frank
Subject: Re: Is this a bug in 3.6.1c?
Date: 9 Mar 2008 05:13:56
Message: <47d3b864$1@news.povray.org>
"Chris B" <nom### [at] nomailcom> schreef in bericht 
news:47d3240f$1@news.povray.org...
>
> "Jaap Frank" <jjf### [at] casemanl> wrote in message 
> news:47d31681$1@news.povray.org...
>> Hi,
>>
>> Recently I stumbled over a link to Chris Bartlett's StairCase macro
>> and downloaded the files.
>> The first example in StairCaseDoc.pov traced happily in about 7s
>> with my AMD Athlon 64 3000+ on Windows XP Home SP2.
>> Because all the examples trace as an animation, I started it with
>> +kfi0 +kff50 in the command line box and went doing something
>> else. After a while I checked the progress and noticed that the
>> tracing was very slow compared to the single trace before.
>> I quickly checked the messages for the first example and good only
>> see a difference in the number of objects :
>> Single trace: 176                Trace time: 7sec
>> Animation:   168                Trace time: 68sec
>> Weird, why is there a difference when everything in the file stays the
>> same?
>
> The 'StairCaseDoc.pov' file is designed to use the animation feature to 
> regenerate all of the 50 different images in the documentation provided 
> with the macros. When you use the animation feature with this file, the 
> SDL uses the frame number to work out which image to generate, then sets 
> the macro parameters for that image. Some of the images contain simple 
> single flights of stairs with a small number of objects, others contain 
> multiple flights of stairs with a very large number of objects. The render 
> time therefore varies a lot from image to image/frame to frame.
>
>> All my animation files are based on clock values and I never
>> noticed any differences in trace time with a single trace or in
>> an animation. However I never used the frame system of POV.
>> In news.povray.org I can't find any reference to such a behaviour.
>
> Even if you just use the clock and don't vary the contents of the scene 
> between frames, the render times for different frames can still vary 
> depending on the proximity to the camera of different objects. For 
> example, a partially transparent or reflective sphere a long way from the 
> camera has less impact on render times than if it's close to the camera 
> and generates additional rays to trace.
>
> Regards,
> Chris B.
>

I'm afraid you miss the point. It's about the same example: number 1. The 
first
is traced with the first line of your StairCaseDoc.pov en the second with 
the
animation option from the second line. They are the same and should trace
equally fast, but with the animation the automatic bounding and the vista
buffer aren't working. You can check that in the statistics (see 
messages.txt).
I've checked the other examples too of coarse and everything stays the same,
no bounding and vista buffer in the animation. Some how they are not
working.

By the way, a very good macro!

Greetings,

Jaap Frank


Post a reply to this message

From: Chris B
Subject: Re: Is this a bug in 3.6.1c?
Date: 9 Mar 2008 09:14:55
Message: <47d3f0df$1@news.povray.org>
"Jaap Frank" <jjf### [at] casemanl> wrote in message 
news:47d3b864$1@news.povray.org...
> "Chris B" <nom### [at] nomailcom> schreef in bericht
> I'm afraid you miss the point. It's about the same example: number 1. The 
> first is traced with the first line of your StairCaseDoc.pov en the second 
> with the
> animation option from the second line. They are the same and should trace
> equally fast, but with the animation the automatic bounding and the vista
> buffer aren't working. You can check that in the statistics (see 
> messages.txt).
> I've checked the other examples too of coarse and everything stays the 
> same,
> no bounding and vista buffer in the animation. Some how they are not
> working.
>

Ah. I see you're right. After a little more investigation, my conclusion is 
that it stems from the fact that the first frame (frame '0') is empty. If 
you use +kfi1 +kff50 then I think you should find the problem goes away. The 
only stuff the scene file does during frame 0 is to clear down the list of 
file names used to rename the files for inclusion in the documentation, so 
you probably won't need that.

I vaguely recall a discussion about starting an animation with no objects in 
the first frame a while ago and reading that POV-Ray makes some assumptions 
(maybe about bounding/vista buffering, I can't remember exactly) and that 
the assumption then lasts for the entire animation sequence. If memory 
serves me correctly I think the conclusion of that discussion was that it 
was more a 'feature' than a 'bug'.

I didn't remember having done this myself in this scene file. If you add SDL 
for image 0 with just 3 spheres in it the problem goes away for +kfi0 
+kff50. Add just 1 or 2 spheres and you still get the slow-down.

> By the way, a very good macro!

Thanks,
Chris B.


Post a reply to this message

From: Jaap Frank
Subject: Re: Is this a bug in 3.6.1c?
Date: 9 Mar 2008 11:12:58
Message: <47d40c8a@news.povray.org>
"Chris B" <nom### [at] nomailcom> schreef in bericht 
news:47d3f0df$1@news.povray.org...
>
> "Jaap Frank" <jjf### [at] casemanl> wrote in message 
> news:47d3b864$1@news.povray.org...
>> "Chris B" <nom### [at] nomailcom> schreef in bericht
>> I'm afraid you miss the point. It's about the same example: number 1. The 
>> first is traced with the first line of your StairCaseDoc.pov en the 
>> second with the
>> animation option from the second line. They are the same and should trace
>> equally fast, but with the animation the automatic bounding and the vista
>> buffer aren't working. You can check that in the statistics (see 
>> messages.txt).
>> I've checked the other examples too of coarse and everything stays the 
>> same,
>> no bounding and vista buffer in the animation. Some how they are not
>> working.
>>
>
> Ah. I see you're right. After a little more investigation, my conclusion 
> is that it stems from the fact that the first frame (frame '0') is empty. 
> If you use +kfi1 +kff50 then I think you should find the problem goes 
> away. The only stuff the scene file does during frame 0 is to clear down 
> the list of file names used to rename the files for inclusion in the 
> documentation, so you probably won't need that.
>
> I vaguely recall a discussion about starting an animation with no objects 
> in the first frame a while ago and reading that POV-Ray makes some 
> assumptions (maybe about bounding/vista buffering, I can't remember 
> exactly) and that the assumption then lasts for the entire animation 
> sequence. If memory serves me correctly I think the conclusion of that 
> discussion was that it was more a 'feature' than a 'bug'.
>
> I didn't remember having done this myself in this scene file. If you add 
> SDL for image 0 with just 3 spheres in it the problem goes away for +kfi0 
> +kff50. Add just 1 or 2 spheres and you still get the slow-down.
>
>> By the way, a very good macro!
>
> Thanks,
> Chris B.
>

Yes, that was the problem. Now it is tracing with the right speed.
Thanks for the reaction.

Jaap Frank


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