I'm rendering a sequence of frames in which certain objects in the scene
rotate, but most of the scene stays the same from frame to frame.

I just happened to be looking at the Messages window during the rendering,
and noticed that each frame seems to take longer than the last to render.
E.g. the first frame took 15 minutes, the next took 17, and so on until
8 or 9 frames later it was taking 28 minutes.

This would be understandable to me if the scene were changing in complexity
from one frame to the next, but as far as I can tell it is equally complex
in each frame.

Has anyone noticed this phenomenon before?  I saw there was a thread earlier
this month asking about increasing amounts of RAM being used in each frame;
it's possible the two issues are related (I haven't been watching the RAM
usage).  However, I'm using v3.6, not v3.5.

[Warning: slight digression follows]  It reminds me of the time I did an
"animation" to test the various radiosity presets.  I set up a fixed scene
(i.e. didn't use clock anywhere) and set the Radiosity_Settings value to
frame_number.  Then I started up a 10-frame "animation" and left the
computer for a few hours while it cranked through them.  Except I didn't
want it to do the REALLY slow settings such as Final or OutdoorHQ, so I
put in a little if/then that set the Radiosity_Settings to 0 (i.e. Default)
for both of those.  Much to my surprise, the first time it ran with Default
it took four hours to render, but later when it ran with Default again it
took less than 1/2 an hour.  Same scene, same radiosity preset, 8x diff
in rendering time.  Never did figure that one out!

But anyway, back to my question:  Does anyone know of anything that POV-Ray
does while rendering an animation sequence that would explain why very
similar frames would take successively longer to render?

Thanks,
wr.

Post a reply to this message

"White Ryder" <nomail@nomail> wrote in message 
news:web.43fce6995f972968fc5d75160@news.povray.org...
> I'm rendering a sequence of frames in which certain objects in the scene
> rotate, but most of the scene stays the same from frame to frame.

If AA is being used there's a chance that could influence render time by an 
observable amount, also such things as refraction and reflection might make 
a significant change.

> I just happened to be looking at the Messages window during the rendering,
> and noticed that each frame seems to take longer than the last to render.
> E.g. the first frame took 15 minutes, the next took 17, and so on until
> 8 or 9 frames later it was taking 28 minutes.
>
> This would be understandable to me if the scene were changing in 
> complexity
> from one frame to the next, but as far as I can tell it is equally complex
> in each frame.

Even so, as I said at first, there could be a possibility of AA and other 
factors causing a difference in render times as the objects move. Of course, 
I'm mostly guessing at this.

> Has anyone noticed this phenomenon before?  I saw there was a thread 
> earlier
> this month asking about increasing amounts of RAM being used in each 
> frame;
> it's possible the two issues are related (I haven't been watching the RAM
> usage).  However, I'm using v3.6, not v3.5.

There's more than one version 3.6 so that could be a factor somehow. Latest 
is 3.6.1b, with 1a before that, and again 3.6.0 before that. Can't recall 
how many were actually released to the public.

> 8<---snip---8< the first time it ran with Default (radiosity)
> it took four hours to render, but later when it ran with Default again it
> took less than 1/2 an hour.

That's a big difference. I'd say background processes running at the same 
time during part of it could possibly explain it, if not POV itself doing 
something to slow it down or speed it up.

> Does anyone know of anything that POV-Ray
> does while rendering an animation sequence that would explain why very
> similar frames would take successively longer to render?

I know this has been a subject of discussion in the past, unfortunately I 
don't remember anything concrete about it. I also searched (only this 
newsgroup) for something similar, although I didn't find anything to point 
you to. I can vaguely recall something about loading of image maps or maybe 
a writing of temporary files being an issue with rendering in succession, 
I'm just not absolutely positive about anything so I'll leave this to others 
to talk about.

Be sure to check your version there, anyhow, in the Help|About or when first 
starting POV. More often than not it helps everyone else to know precisely 
which you're using.

Bob H

Post a reply to this message

"White Ryder" <nomail@nomail> wrote:
> But anyway, back to my question:  Does anyone know of anything that POV-Ray
> does while rendering an animation sequence that would explain why very
> similar frames would take successively longer to render?
>

I’ve had similar problems with some scenes. It is possible that you
have a memory leak. If you are using windows you can check using the Task
Manager. My work around is to split the frames using a couple of INI files
with contiguous Subset_Start_Frame and Subset_End_Frame then use the render
queue to render them in sequence.
E.g.

Scene01.ini

Initial_Frame=1
Final_Frame=30
Subset_Start_Frame=1
Subset_End_Frame=1
Input_File_Name= Scene.pov

Scene02.ini

Initial_Frame=1
Final_Frame=30
Subset_Start_Frame=2
Subset_End_Frame=2
Input_File_Name= Scene.pov


And so on.

Stephen

Post a reply to this message

you could use my "distributed render system for animations" script in
POV-Ray > Newsgroups > povray.text.scene-files.

i't ecentially a dos batchfile that repeatetly runs a special povray file.
that povray file generates "render comamnds" (also a batch file) for all
connected computers.

I have tested it running the master and the render client on the same pc, so
it should work using just one pc. it restarts megapov for each frame with
apropreate start and end frame settings (to render a single frame each
time).

using a shared folder on a network, it can ditribute frames over all the
pc's in the network. I have run in to the XP limit (max. 10 pc's on a
shared folder) but with 9 PC's it works like a runawy train :-)

Post a reply to this message

"Jaap" <jws### [at] yahoocom> wrote:
> you could use my "distributed render system for animations" script in
> POV-Ray > Newsgroups > povray.text.scene-files.
>
> i't ecentially a dos batchfile that repeatetly runs a special povray file.
> that povray file generates "render comamnds" (also a batch file) for all
> connected computers.
>
> I have tested it running the master and the render client on the same pc, so
> it should work using just one pc. it restarts megapov for each frame with
> apropreate start and end frame settings (to render a single frame each
> time).
>
> using a shared folder on a network, it can ditribute frames over all the
> pc's in the network. I have run in to the XP limit (max. 10 pc's on a
> shared folder) but with 9 PC's it works like a runawy train :-)

I would like also to know why it takes more and more time.
For the test, I use exactely the same file with exactely the same parameters
between 2 renderings. The 1st time is always faster than the other time /
the other rendering. There isn't any other program which runs. Only
POV-Ray.

Someone can help?

Windows2000 SP4 Athlon 1800+ 1Giga RAM

thks
Vincent

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