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From: Tom Stone
Subject: Field rendering?
Date: 17 Oct 2001 12:53:39
Message: <tom.stone-1710011917550001@d212-151-230-43.swipnet.se>
This isn't a request, just something that I'm curious about.

In "5.2.1.5 Field Rendering" in the documentation, it says:

"Field rendering is sometimes used for animations when the animation is
being output for television".

Is it possible to get a better definition of "sometimes" in that sentence?
When is it necessary to use this option? Do I need to use it if I'm going
to process the animation further in another program (Premiere,
AfterEffects, etc.)

I'm thinking of making an instructional video tape sometime next year, and
I'm thinking of including a few povray animations, but it would be
frustrating if I had to render everything again just because I've
misunderstood this option.

It would be great if there are any pov user with TV experience that could
add a few pointers about field rendering in the documentation, or perhaps
just give a few hints of where to search for such information.

However, if this is a bad idea, just ignore this posting.

-- 
Tom Stone
Domarebacken 42, 14557 Norsborg, Sweden
Phone: Int+46 8 5318 4318, Tel: 08-5318 4318
http://home5.swipnet.se/~w-52256/index.htm


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From: Dennis Milller
Subject: Re: Field rendering?
Date: 17 Oct 2001 13:18:23
Message: <3bcdbd5f$1@news.povray.org>
I have made many dozens of POV animations that went from PC (via Premiere)
to videotape to TV. I've never set field rendering. It's possible Premiere
is doing something when I output the work to tape, but I'm not sure of that.
Do you have a way to transfer the video to tape, and if so, maybe give it a
try?
d.

"Tom Stone" <tom### [at] swipnetse> wrote in message
news:tom### [at] d212-151-230-43swipnetse...
> This isn't a request, just something that I'm curious about.
>
> In "5.2.1.5 Field Rendering" in the documentation, it says:
>
> "Field rendering is sometimes used for animations when the animation is
> being output for television".
>
> Is it possible to get a better definition of "sometimes" in that sentence?
> When is it necessary to use this option? Do I need to use it if I'm going
> to process the animation further in another program (Premiere,
> AfterEffects, etc.)
>
> I'm thinking of making an instructional video tape sometime next year, and
> I'm thinking of including a few povray animations, but it would be
> frustrating if I had to render everything again just because I've
> misunderstood this option.
>
> It would be great if there are any pov user with TV experience that could
> add a few pointers about field rendering in the documentation, or perhaps
> just give a few hints of where to search for such information.
>
> However, if this is a bad idea, just ignore this posting.
>
> --
> Tom Stone
> Domarebacken 42, 14557 Norsborg, Sweden
> Phone: Int+46 8 5318 4318, Tel: 08-5318 4318
> http://home5.swipnet.se/~w-52256/index.htm


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From: Vampyrium
Subject: Re: Field rendering?
Date: 17 Oct 2001 14:45:23
Message: <3bcdd1c3@news.povray.org>
-Hail

  Field rendering is absolutely necesary if your output is video (ntsc or
pal) if you wish to achieve smooth motion. Unfortunately i have never had
any luck with the field render in POV. POV claims to do field rendering but
it doesnt really, ths feature is absolutely useless, i dont know why it is
even there, it should either be removed or fixed.
  Field rendering should render alternate scanlines (odd and even fields) on
the SAME frame at DIFFERENT timepoints (at frame in-point and frame
mid-point) any other solution is not a solution as you need other software
to compile the animation by using two half res images to make a whole or
double frame rate and half of each frame is used.


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From: Tom Stone
Subject: Re: Field rendering?
Date: 18 Oct 2001 07:48:35
Message: <tom.stone-1810011412530001@d212-151-166-213.swipnet.se>
In article <3bcdbd5f$1@news.povray.org>, "Dennis Milller"
<dhm### [at] mediaonenet> wrote:

>I have made many dozens of POV animations that went from PC (via Premiere)
>to videotape to TV. I've never set field rendering.

Good to know. Thanks.
So, it isn't necessary to use this option when processing it further in
dedicated video editing software.
Is it ever necessary to use this option at all?

>Do you have a way to transfer the video to tape, and if so, maybe give it a
>try?

I will have, but not until the spring.

-- 
Tom Stone
Domarebacken 42, 14557 Norsborg, Sweden
Phone: Int+46 8 5318 4318, Tel: 08-5318 4318
http://home5.swipnet.se/~w-52256/index.htm


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From: Tom Stone
Subject: Re: Field rendering?
Date: 18 Oct 2001 07:59:37
Message: <tom.stone-1810011423550001@d212-151-166-213.swipnet.se>
In article <3bcdd1c3@news.povray.org>, "Vampyrium" <cyb### [at] hotmailcom>
wrote:
>  Field rendering is absolutely necesary if your output is video (ntsc or
>pal) if you wish to achieve smooth motion. Unfortunately i have never had
>any luck with the field render in POV.

What do you do instead?

>POV claims to do field rendering but
>it doesnt really, ths feature is absolutely useless, i dont know why it is
>even there, it should either be removed or fixed.

I don't know enough to have an opinion. Can anyone else confirm or refute?

-- 
Tom Stone
Domarebacken 42, 14557 Norsborg, Sweden
Phone: Int+46 8 5318 4318, Tel: 08-5318 4318
http://home5.swipnet.se/~w-52256/index.htm


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From: Thorsten Froehlich
Subject: Re: Field rendering?
Date: 18 Oct 2001 08:04:41
Message: <3bcec559@news.povray.org>
In article <tom### [at] d212-151-166-213swipnetse> , 
tom### [at] swipnetse (Tom Stone) wrote:

> Good to know. Thanks.
> So, it isn't necessary to use this option when processing it further in
> dedicated video editing software.
> Is it ever necessary to use this option at all?

Yes, but only if your frame rate is matching the interlaced frame rate you
will see a difference.  If you render only 25/30 frames (for PAL/NTSC video
output) you will not see a difference because the video program will simply
use the same image and do the necessary conversion to an interlaced format
automatically.  It is different if you want to output with a framerate that
does _match_ the interlaced frame rate of your video system.  So if you
output with 50/60 frames/second you do want to use this option as is allows
you to reduce render time because POV-Ray will only need to render half as
many lines.  Of course you could also render it without this flag, but the
whole rendering will take twice as long and the output program will just end
of throwing away half of your work...

Note: The above is only true if you do a full resolution PAL/NTSC output.
Meaning 768*576 for PAL and 640*480 for NTSC with 50/60 frames per second
with field rendering.  If you use half of resolution, i.e. 384*288 or
320*240 you gain nothing with field rendering - only using 25/30 full frames
per second makes sense for this resolution or any other resolution below the
native resolution of PAL/NTSC.


    Thorsten


____________________________________________________
Thorsten Froehlich, Duisburg, Germany
e-mail: tho### [at] trfde

Visit POV-Ray on the web: http://mac.povray.org


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From: Thorsten Froehlich
Subject: Re: Field rendering?
Date: 18 Oct 2001 08:10:34
Message: <3bcec6ba@news.povray.org>
In article <3bcdd1c3@news.povray.org> , "Vampyrium" <cyb### [at] hotmailcom>
wrote:

>   Field rendering should render alternate scanlines (odd and even fields) on
> the SAME frame at DIFFERENT timepoints (at frame in-point and frame
> mid-point) any other solution is not a solution as you need other software
> to compile the animation by using two half res images to make a whole or
> double frame rate and half of each frame is used.

Of course you need other software to do it, that is the whole point!  I am
not aware of any external software that can handle an image file the way you
expect POV-Ray to output it.  On the other hand, I know plenty of software
that imports the output POV-Ray currently generates.

The field rendering in POV-Ray is working exactly the way it should and I
have successfully output POV animations to video with field rendering.


    Thorsten


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From: Tom Stone
Subject: Re: Field rendering?
Date: 18 Oct 2001 08:30:12
Message: <tom.stone-1810011454300001@d212-151-166-213.swipnet.se>
In article <3bcec559@news.povray.org>, "Thorsten Froehlich"
<tho### [at] trfde> wrote:

>If you render only 25/30 frames (for PAL/NTSC video
>output) you will not see a difference because the video program will simply
>use the same image and do the necessary conversion to an interlaced format
>automatically.  It is different if you want to output with a framerate that
>does _match_ the interlaced frame rate of your video system.  So if you
>output with 50/60 frames/second you do want to use this option as is allows
>you to reduce render time because POV-Ray will only need to render half as
>many lines.
>Note: The above is only true if you do a full resolution PAL/NTSC output.
>Meaning 768*576 for PAL and 640*480 for NTSC with 50/60 frames per second
>with field rendering.  If you use half of resolution, i.e. 384*288 or
>320*240 you gain nothing with field rendering - only using 25/30 full frames
>per second makes sense for this resolution or any other resolution below the
>native resolution of PAL/NTSC.

Thanks Thorsten!
This is valuable information indeed. Is it wrong to ask if this could be
included in the documentation?

-- 
Tom Stone
Domarebacken 42, 14557 Norsborg, Sweden
Phone: Int+46 8 5318 4318, Tel: 08-5318 4318
http://home5.swipnet.se/~w-52256/index.htm


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From: Vampyrium
Subject: Re: Field rendering?
Date: 19 Oct 2001 00:03:14
Message: <3bcfa602@news.povray.org>
-Hail

  This information is wrong again. Check out any video output software and
you will see what i mean. I have worked with video for over a year and I
know exactly why POV material cannot be used (properly) unless you have
digital fusion which can fix fields (and this option is neither easy or
cheap!). It simply because its fileld rendering capability is just not what
it should be. You cannot have a smooth animation with two identical fields.
If you insist on this being the way it should be I wil have to post some
clear example images as this is an important feature that has gone terribly
wrong.


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From: Ze!nPsycho
Subject: Re: Field rendering?
Date: 19 Oct 2001 01:23:20
Message: <3bcfc85a.47724673@news.povray.org>
Ok so the way a tv does things is like this


it renders the odd lines, and then the even lines, 
and that process goes 30 times a second, or 60 full scans per second.

normally on 30 fps video, it just scans the odd, and even lines of the
same image. 30 fps. Though if you feild render an animation at 60 fps.
Frame 1 on the odd lines frame 2 on the even lines. then on the second
image frame 3 on the odd, frame 4 on the even, etc... you can achieve
60 frames per second on an ntcs video screen.  Thus interlaced images
in the way vampir described are neccesary for 60 fps.


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