Thorsten Froehlich wrote:

> 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)

[SNIP]

> 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.

When I was working with video (U-matic, S-VHS and Digital Beta tape, CubiComp,
NuVista, Targa and other hardware, Picture Maker, Macromind3d, 3D-Studio,
Stratavision, Lightwave and other software), the kind of image Vamp mentioned was
the type of image we worked with.

I'll have to run POV through some checks to see exactly what it's doing... and
how it's output can be piped properly to broadcast. It could be as simple as
compositing frames from fields in post (which seems to be what Thorsten is
saying). IIRC, when I looked into this in 3.1, I said to myself something like
"oh, that's strange... hmmm.... Ah, I see. Still useful". Now I just have to
remember the details of all that.


In the meantime, here are a few quick links I found on google

http://www.mcqpro.com/html/FieldRendering.html

http://www.greatdv.com/video/fields.htm

http://www.adobe.com:80/support/techdocs/102b2.htm

Nice field diagrams:
http://www.lurkertech.com/lg/fields/fields.html

http://www.commotionpro.com/support/white_papers/fields.html

http://www.puremotion.com/videoediting/reference/technical/interlacedvideoexplained/

--
Jon A. Cruz
http://www.geocities.com/joncruz/action.html

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In article <3bcfa602@news.povray.org> , "Vampyrium" <cyb### [at] hotmailcom>
wrote:

> You cannot have a smooth animation with two identical fields.

Identical fields?  I think we are talking about something different because
POV-Ray does not output identical fields as far as I know...


    Thorsten


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

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

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"Thorsten Froehlich" <tho### [at] trfde> wrote in message
news:3bcfce5c$1@news.povray.org...
> In article <3bcfa602@news.povray.org> , "Vampyrium"
<cyb### [at] hotmailcom>
> wrote:
>
> > You cannot have a smooth animation with two identical fields.
>
> Identical fields?  I think we are talking about something different
because
> POV-Ray does not output identical fields as far as I know...

Could it be that in video the fields are acting as independant frames, i.e.
motion between the odd and even?  I've heard things about this over the
years but I have no idea if anyone ever brought that up before.  I never
learned much on the subject nor did any actual video use of it.  Animating
in mpeg it turns out pretty bad as I recall.  I had thought the two images
were merged into a single frame somehow when using the appropriate hardware.

Bob H.

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Wish I had checked the other replies before doing so myself.

Seems the idea then is for each field to be a independant time-based
subframe, as per what POV-Ray supposedly does, as I reread that section of
the doc.

So... I don't understand what the matter is  :-)

Bob H.

"Jon A. Cruz" <jon### [at] geocitiescom> wrote in message
news:3BCFC1E8.529E28A2@geocities.com...
> Thorsten Froehlich wrote:
>
> > 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)
>
> [SNIP]
>
> > 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.
>
> When I was working with video (U-matic, S-VHS and Digital Beta tape,
CubiComp,
> NuVista, Targa and other hardware, Picture Maker, Macromind3d, 3D-Studio,
> Stratavision, Lightwave and other software), the kind of image Vamp
mentioned was
> the type of image we worked with.
>
> I'll have to run POV through some checks to see exactly what it's doing...
and
> how it's output can be piped properly to broadcast. It could be as simple
as
> compositing frames from fields in post (which seems to be what Thorsten is
> saying). IIRC, when I looked into this in 3.1, I said to myself something
like
> "oh, that's strange... hmmm.... Ah, I see. Still useful". Now I just have
to
> remember the details of all that.
>
>
> In the meantime, here are a few quick links I found on google
>
> http://www.mcqpro.com/html/FieldRendering.html
>
> http://www.greatdv.com/video/fields.htm
>
> http://www.adobe.com:80/support/techdocs/102b2.htm
>
> Nice field diagrams:
> http://www.lurkertech.com/lg/fields/fields.html
>
> http://www.commotionpro.com/support/white_papers/fields.html
>
>
http://www.puremotion.com/videoediting/reference/technical/interlacedvideoex
plained/
>
> --
> Jon A. Cruz
> http://www.geocities.com/joncruz/action.html
>
>
>

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"Bob H." wrote:
> 
> Wish I had checked the other replies before doing so myself.
> 
> Seems the idea then is for each field to be a independant time-based
> subframe, as per what POV-Ray supposedly does, as I reread that section of
> the doc.
> 
> So... I don't understand what the matter is  :-)

I think he wants each odd and subsequent even frame
to be combined by POV-Ray in a single image. I think
it can be done by any image manipulation program.
But perhaps I am wrong. I have my own idea of how
frames should work, and feel that both the doc and
the implementation are correct (I didn't actually use
it). What's happening, is that POV perhaps isn't doing
things so that importing the result in popular video
software suites is not trivial, but a bit convoluted.

-- 
Adrien Beau   adr### [at] freefr   http://adrien.beau.free.fr/

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-Hail

  I will post an image and a messa ge on p.b-t.b to clear things up about
this subject.

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Tom Stone wrote:

> In article <3bcdd1c3@news.povray.org>, "Vampyrium" <cyb### [at] hotmailcom>
> wrote:
>
> >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?

OK. I just checked into it.

Here's where it comes out not so handy.

Say I have an animation. I set it up carefully. I go to render it. Say I
render 640x480, 300 frames. I take the 30 output frames and make an MPEG or
divx or whatever out of it. Of course, I set it to be 30 fps. I get a nice,
ten second animation that plays well on my computer.

Now I decide that since I have access to a nice, single-frame recorder video
deck (SVHS, not Digital Beta - I'm not that right), I'd like to put it on
video to show my friends. Oooh, lookit dat! POV-Ray does field rendering!!! So
I got and add "+UF" and re-render my animation.

Hmmm... Strange, it's not interleaved. OK, I R_FM. Ahhh, every two output
files need to be combined. So I go and get something setup to combine those
two images for output. Whew. Lot's of file munging later it's ready. I go and
dump it to video, using my single-frame recorder.

Oh no! My beautiful animation is now only 5 seconds long, and it's speeded
up!! Woe! Dismay! Gnashing of Teeth!!!!


Well, OK. It's not the end of the world, but it is annoying. Using the 'field
rendering' switch effectively changes POV-Ray from outputting frames to
outputting fields. So in one sense it is technically accurate as to being a
"field rendering" option. On the other hand, other 3D packages will still
output the same number of files, but then go on to put two fields per file. So
POV-Ray is different from those.

Of course, it might be hard to make POV-Ray do two rendering passes per one
output file, so there may be technical limitations to getting it changed.

Then again, there's that lingering problem of the clock values being off.
Sigh. No easy fix here.

BTW, it's quite amusing that the preview mode under Unix/Linux happens to
collect up the fields and make you think it's doing the right thing :-)   [see
my posting of one under p.b-t.b]


--
Jon A. Cruz
http://www.geocities.com/joncruz/action.html

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"Jon A. Cruz" wrote:

> deck (SVHS, not Digital Beta - I'm not that right), I'd like to put it on

That was supposed to be "rich", not "right". Sigh. I guess that's what I get for
trying to be funny while being distracted by the kids.


--
Jon A. Cruz
http://www.geocities.com/joncruz/action.html

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In article <3BD1F27A.C6FF05FF@geocities.com> , "Jon A. Cruz" 
<jon### [at] geocitiescom> wrote:

> Well, OK. It's not the end of the world, but it is annoying. Using the 'field
> rendering' switch effectively changes POV-Ray from outputting frames to
> outputting fields. So in one sense it is technically accurate as to being a
> "field rendering" option. On the other hand, other 3D packages will still
> output the same number of files, but then go on to put two fields per file. So
> POV-Ray is different from those.

Yes, one has to double the number of steps by outputting twice as many
images...

BTW, when using VHS to record the output it is usually enough to render only
with about 256 pixels width and use simple smooth interpolation because VHS
has hardly more resolution and at it is hard to see the difference.  As for
SVHS, I only used to output to it once or twice (not for myself - I can't
afford SVHS VCRs) and with 384 pixels horizontal resolution I still got good
results.  Of course as I didn't try with 768 pixels in the first place, I
can't say if it would have been better*.


    Thorsten


* Using a Beige G3 with the full size video I/O board (there are two
versions and only the one with the HW DVD player supports full res output in
the first place!)

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

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

Post a reply to this message

In article <3BD1F27A.C6FF05FF@geocities.com>, "Jon A. Cruz"
<jon### [at] geocitiescom> wrote:

>Using the 'field
>rendering' switch effectively changes POV-Ray from outputting frames to
>outputting fields. So in one sense it is technically accurate as to being a
>"field rendering" option. On the other hand, other 3D packages will still
>output the same number of files, but then go on to put two fields per file. So
>POV-Ray is different from those.

Hello Jon,

Since there is a difference in how Field Rendering is handled in Pov-Ray
and in other 3-D packages, then perhaps this difference should be
documented?

You seem to posess a lot more knowledge than me about these things. Do you
think that you could look at "5.2.1.5 Field Rendering" in the docs and see
if you can think of a more detailed description of this feature?
(Of cource, then it is up to the POV-team to decide if a change in the
docs is needed here).

-- 
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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