Reading through some of the posts here I can see that there is quite a bit
of confusion about how POV implements its field rendering. If you have a
look back at my earlier posting it describes how the lines and fields are
output by POV. Yes, like 3DS or other programs it needs to parse the scene
twice for each frame because in an animation the position of objects will
have changed between the two fields.

The problem is that in POV the two fields are output to two separate files
which is quite bizzare. And each field/file has alternate lines which are
redundant. Thorsten says he believes that "Premiere" and other editing
programs must have a feature that can interleave the POV file/fields and
that he therefore can't see the problem - I'm not so sure that such features
exist which can interleave POV fields correctly. As I expalined earlier the
"interleave frames" feature on Premiere doesn't do what is required to merge
POV field-pair files into single properly interleaved frames (actually it
goes part of the way but you would then need to delete alternate frames in
Premiere because the alternate frames are comprised of the redundant lines
from the POV output targa files). I may be wrong but I can't see that an
editing program would need a feature which performed the kind of interlacing
which the POV files require.

What POV ought to do when field rendering is switched on, is to create a new
numbered targa file only for fields 1, 3, 5, etc and to write the "odd"
field lines into the file; and then for fields 2, 4, 6 etc it should RE-OPEN
the previous file and write the "even" lines between the previously written
odd lines. Then you would end up with half the number of files and each file
would contain a complete and properly interleaved frame.

I can't see why POV should not do field-rendering this way, it would remove
a lot of the hassle of trying to merge the exiting output files. I know that
POV needs to calculate the redundant lines in memory if anti-aliasing is
switched on, but there's nothing to stop it only outputting the alternate
"used" lines to file.

I have just about finished a program which will do this interlacing, but it
really shouldn't be necessary.

Incidentally, I'm not to keen on the terms "odd" and "even" when refering to
fields as they are ambiguous, depending on whether you start counting from
line 1 or 0. When someone mentions the "odd" field you really can't be sure
which they mean. Unfortunately POV uses this terminology and appears to
start at line 0. I wish they would use "upper" or "lower" field instead as
this is unambiguous.

Colin


"Thorsten Froehlich" <tho### [at] trfde> wrote in message
news:3cd2db83@news.povray.org...
> In article <vnv4du0p2ditk649ustosq2er9jueubqbm@4ax.com> , Scott Moore
> <sdm### [at] zoomcouk>  wrote:
>
> > On second thoughts, I won't post some images - I see where you're
> > coming from. <thinking out loud> If you want a 100 frame interlaced
> > animation you need to produce 200 images using POV with field
> > rendering turned on and then use another tool to interlace them into
> > the final 100 frames. Hmm, 3ds max is doing this final step for you.
>
> You are not the first person to be confused about this.  I suppose I small
> note about this littel but important difference should be added to the
> documentation...
>
>
>     Thorsten
>
>
> ____________________________________________________
> Thorsten Froehlich, Duisburg, Germany
> e-mail: tho### [at] trfde
>
> Visit POV-Ray on the web: http://mac.povray.org

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