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Is there any possibility that anti-aliasing uses a rand function? Did you
render this with AA on or off?
Julius Klatte <jku### [at] hotmail com> wrote in message
news:370e8cb3.0@news.povray.org...
> Strange...
> I always thought that POV-ray's rendered images were always
> exactly the same for the same code, like with 'normal'(?)
> instructions.
>
> Example: if you calculate tan 1 with a calculator, you
> always
> get the same result: 1.55740772465490223050697480745836(...)
>
> However, it appears this doesn't work this way for POV-ray
> image output (?).
> I've rendered the same POV code more than once on the same
> computer without using any jittering or crand or any other
> random
> function that I know of. The results were slightly
> different, as
> you can see in the attached image (that's why I posted it in
> this group)
> (close-ups of the rendered images).
> Can anybody tell me why the output is different?
>
> Just wondering...
>
> Julius
>
>
>
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In answer to your (pretty quick!) reactions:
>Did you use any #macros or looping runs (#if #while,
etc.) ?
No. But that shouldn't influence the render result either...
>Maybe it's gremlins.
Hmmm... there's an interesting suggestion...
>What do you want for free ?
I'm not complaining!
>Have you checked for viruses lately?
Yes. I spoke to some of them yesterday. But they didn't tell
me: "Hey, we're not going to mess up your system, just the
tiny details of your POV images." Not that you can trust 'em
of course.
>Did someone turn on a blender or something while the image
was rendering ?
Well, the neighbours were having a fight...
>Seriously I haven't a clue. Sorry.
You're disappointing me... :)
>Is there any possibility that anti-aliasing uses a rand
function? Did you
>render this with AA on or off?
That was my first guess as well. I'm not sure if
anti-aliasing is random. I always thought it was a standard
per-pixel routine.
The image(s) I attached were with anti-aliasing, but I tried
another time with AA off and that sure made things
blockier..., but still there were slight variations in the
images.
I'm not really having any problem with the phenomenon, since
the effect is invisible for unzoomed rendered images, but it
just struck me as strange...
Thanks anyway
Julius
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I don't have an answer either, but from the looks of this image, which
looks to be enlarged to almost the nonoscopic level:-) you could hardly
notice these variances.
Julius Klatte wrote:
> Strange...
> I always thought that POV-ray's rendered images were always
> exactly the same for the same code, like with 'normal'(?)
> instructions.
>
> Example: if you calculate tan 1 with a calculator, you
> always
> get the same result: 1.55740772465490223050697480745836(...)
>
> However, it appears this doesn't work this way for POV-ray
> image output (?).
> I've rendered the same POV code more than once on the same
> computer without using any jittering or crand or any other
> random
> function that I know of. The results were slightly
> different, as
> you can see in the attached image (that's why I posted it in
> this group)
> (close-ups of the rendered images).
> Can anybody tell me why the output is different?
>
> Just wondering...
>
> Julius
>
> [Image]
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It is most definitely the AA. That is random in it's treatment of
pixels. You've really got me there on how it looks different even with
AA off. The only logical explanation is the gremlins, as Mr. Tyler
suggested.
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Try the same code numerous times on another computer.
GrimDude
vos### [at] arkansasnet
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'jitter' as you all might know is random on a frame by frame basis, not
to be used when making animation frames you know.
If no AA there is no jitter as I understood it, but makes me wonder now.
It has the ability to be on, off, off with a number which will be used
on the next render, etc. so maybe the answer lies there.
Julius Klatte wrote:
>
> In answer to your (pretty quick!) reactions:
>
> >Did you use any #macros or looping runs (#if #while,
> etc.) ?
> No. But that shouldn't influence the render result either...
>
> >Maybe it's gremlins.
> Hmmm... there's an interesting suggestion...
> >What do you want for free ?
> I'm not complaining!
> >Have you checked for viruses lately?
> Yes. I spoke to some of them yesterday. But they didn't tell
> me: "Hey, we're not going to mess up your system, just the
> tiny details of your POV images." Not that you can trust 'em
> of course.
> >Did someone turn on a blender or something while the image
> was rendering ?
> Well, the neighbours were having a fight...
> >Seriously I haven't a clue. Sorry.
> You're disappointing me... :)
>
> >Is there any possibility that anti-aliasing uses a rand
> function? Did you
> >render this with AA on or off?
> That was my first guess as well. I'm not sure if
> anti-aliasing is random. I always thought it was a standard
> per-pixel routine.
> The image(s) I attached were with anti-aliasing, but I tried
> another time with AA off and that sure made things
> blockier..., but still there were slight variations in the
> images.
>
> I'm not really having any problem with the phenomenon, since
> the effect is invisible for unzoomed rendered images, but it
> just struck me as strange...
>
> Thanks anyway
>
> Julius
--
omniVERSE: beyond the universe
http://members.aol.com/inversez/homepage.htm
mailto:inv### [at] aolcom?Subject=PoV-News
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This phenomenon appears to me to be cyclical, suggesting that it
may be memory getting full, and clearing out and starting again,
something like that.
We know nothing about the size of the whole image, the object
count, are you using atmosphere, I'm sure that has some random
factor, media too.
I'd be tempted to look at the code.
Steve
Julius Klatte wrote:
>
> Strange...
> I always thought that POV-ray's rendered images were always
> exactly the same for the same code, like with 'normal'(?)
> instructions.
>
> Example: if you calculate tan 1 with a calculator, you
> always
> get the same result: 1.55740772465490223050697480745836(...)
>
> However, it appears this doesn't work this way for POV-ray
> image output (?).
> I've rendered the same POV code more than once on the same
> computer without using any jittering or crand or any other
> random
> function that I know of. The results were slightly
> different, as
> you can see in the attached image (that's why I posted it in
> this group)
> (close-ups of the rendered images).
> Can anybody tell me why the output is different?
>
> Just wondering...
>
> Julius
>
> [Image]
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+AD4-We know nothing about the size of the whole image, the
object
+AD4-count, are you using atmosphere, I'm sure that has some
random
+AD4-factor, media too.
+AD4-
+AD4-I'd be tempted to look at the code.
I could post the code, but I don't think it would make much
sense. There was no media or atmosphere. At the first render
there were lots of objects in the scene, but I commented all
but one out when I started to look at the tiny details (to
spare some time).
I still think it's just the anti-aliasing. Does any of the
programmers around here know if POV uses a random function
for AA?
I'm going to have another look at the no-AA renders. Maybe
there was no difference after all.. (that would mean no
gremlins either).
It's really an 'academic' problem, for the differences
between the images are invisible... but I'm just curious...
Greetings all
Julius
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From: Lance Birch
Subject: Re: Not always the same render results?? <<<----- WAIT A SECOND THERE!!!
Date: 11 Apr 1999 13:28:11
Message: <3710cd9b.0@news.povray.org>
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Hmm, I've had this problem too... I was trying to get my RLE encoder to work
properly but it wouldn't because the images changed slightly... The way
around it I found was to go into POV-Ray, render... exit POV-Ray, go back in
and render again and you'll get the same image (providing you don't use any
AA jitter or crand).
Then again, it's already @725 here in Australia so I'm tired... I'm going to
sleep... Maybe I'll get in a Lucid Dream if I'm lucky too...
--
Lance.
---
For the latest 3D Studio MAX plug-ins, images and much more, go to:
The Zone - http://come.to/the.zone
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Crand and jitter are the only really random functions... Well, probably
media, too.
Margus
Julius Klatte wrote in message <3710a905.0@news.povray.org>...
>
>I could post the code, but I don't think it would make much
>sense. There was no media or atmosphere. At the first render
>there were lots of objects in the scene, but I commented all
>but one out when I started to look at the tiny details (to
>spare some time).
>
>I still think it's just the anti-aliasing. Does any of the
>programmers around here know if POV uses a random function
>for AA?
>I'm going to have another look at the no-AA renders. Maybe
>there was no difference after all.. (that would mean no
>gremlins either).
>
>It's really an 'academic' problem, for the differences
>between the images are invisible... but I'm just curious...
>
>Greetings all
>
>Julius
>
>
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