Christoph Hormann wrote:

> I personnaly don't see much need to compress single pov code files, since
> otherwise you can directly view them and have less work when downloading.

Yeah, I hate when single small files are zipped up (some with little size benefit
anyway). Then I have to open explorer and unzip it, and PKZip for windows is
incredibly slow to load up and close. Sometimes it's used more as a packaging tool
than a compression tool, which is ok I guess, but if there's an alternative use
it. (Like TI calculator games, just make an .86g or .89g or whatever file).

--
David Fontaine  <dav### [at] faricynet>  ICQ 55354965
My raytracing gallery:  http://davidf.faricy.net/

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Gilles Tran wrote in message <3A5F7662.D8DFB100@inapg.inra.fr>...
>Pcm and mesh2 are text formats, not binary, which makes them portable and
>editable, which are too good reasons. I also guess that zip support is not
>royaltee-free (I could be wrong).


Zip support is free.

--
Mark

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On Fri, 12 Jan 2001 17:51:41 +0100, "Rune" <run### [at] inamecom>
wrote:

>I have some general questions about compression.
>
>I don't know much about different platforms. Is the .zip format accessible
>on all platforms? 

Yes. Well, on 16- and 32-bit platforms, that is :)

>I always zip all my scene files before I upload them to my
>website, but does that exclude some people from using them?

No.

>If .zip is universally supported I have a question about mesh compression:
>what is the reason for the compression used by pcm and mesh2? 

The file gets a) smaller b) better organised and c) readable by POV's
#read directive, which allows for some neat effects such as shown by
Chris' macros.

>Zipping a mesh file is more efficient than using any of those formats, 
>and a zipped regular mesh is even smaller than a zipped pcm or mesh2.

zip uses a Leimpfell-Ziff-Huffman compression algorithm very suitable
for text files. I don't recall if hash tables were a courtesy of LZW
but if not, this would be the explanation. A pcm file reorganises the
data into a more compact form with some data loss.

>I have two guesses myself:
>1) Zip is not universally supported.
>2) The file size while sending the mesh over the net is not the reason for
>compression, but rather the file size on the local HD.

Both guesses are off-the-point as the main purpose of the pcm file
format is to provide the POV parser with access to the mesh component
(vertices, faces, normals, uv indices etc.)


Peter Popov ICQ : 15002700
Personal e-mail : pet### [at] vipbg
TAG      e-mail : pet### [at] tagpovrayorg

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On Fri, 12 Jan 2001 23:10:30 -0000, "Rick [Kitty5]" <ric### [at] kitty5com>
wrote:

>if your going toi use compression - and your should - zip is probably your
>best bet, its about the closest there is to a 'standard'
>
>much better to use zip than say RAR or ACE...

RAR is available for DOS, Windows, Mac and *x. What more is there? :)


Peter Popov ICQ : 15002700
Personal e-mail : pet### [at] vipbg
TAG      e-mail : pet### [at] tagpovrayorg

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David Fontaine wrote:
> 
> Yeah, I hate when single small files are zipped up (some with little size benefit
> anyway). Then I have to open explorer and unzip it, and PKZip for windows is
> incredibly slow to load up and close. Sometimes it's used more as a packaging tool
> than a compression tool, which is ok I guess, but if there's an alternative use
> it. (Like TI calculator games, just make an .86g or .89g or whatever file).
> 

A fast solution for expanding ZIP with the windows explorer is to
associate them with a small batch file invoking regular unzip.exe.  I have
two menu items in the context menu, one for viewing, one for expanding in
a subdirectory named filename.zip.out 

Christoph

-- 
Christoph Hormann <chr### [at] gmxde>
IsoWood include, radiosity tutorial, TransSkin and other 
things on: http://www.schunter.etc.tu-bs.de/~chris/

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"Peter Popov" wrote:
> Both guesses are off-the-point as the main purpose of the
> pcm file format is to provide the POV parser with access
> to the mesh component (vertices, faces, normals, uv indices
> etc.)

I was not asking for the reason for the file format itself, but for the
compression used by that file format, so I think my second guess is not so
much off-the-point after all.

Thanks for the reply anyway. :)
Nice to know that .zip can be used by everybody.

Rune
--
\ Include files, tutorials, 3D images, raytracing jokes,
/ The POV Desktop Theme, and The POV-Ray Logo Contest can
\ all be found at http://rsj.mobilixnet.dk (updated January 6)
/ Also visit http://www.povrayusers.org

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"Chris Colefax" wrote:
> Rune wrote:
> > what is the reason for the compression used by pcm and mesh2?
> >
> > I have two guesses myself:
> > 1) Zip is not universally supported.
> > 2) The file size while sending the mesh over the net is not
> >    the reason for compression, but rather the file size on
> >    the local HD.
>
> This is pretty much the case - ZIP may be an unofficial standard,
> but it's not guaranteed to be available on all platforms, and to
> use the zipped file you have to unzip it first (so the unzipped
> file plus the zipped file means the disk space required while
> using the file is actually larger than the uncompressed file!).

Thank you for clarifying that.

> an uncompressed mesh might the fastest and easiest if you don't
> want to do anything fancy with it, whereas the PCM gives you
> direct control over each vertex, and the mesh2 allows easy
> conversion from other formats, such as UV-mapped models.

I've been experimenting with my own mesh macros, but I've encountered some
problems. The biggest one is about the uv_vectors in mesh2. See p.u.p.

My idea is to create a new format that combines the best from PCM and mesh2.
(It would not support bicubic_patches though.)

Rune
--
\ Include files, tutorials, 3D images, raytracing jokes,
/ The POV Desktop Theme, and The POV-Ray Logo Contest can
\ all be found at http://rsj.mobilixnet.dk (updated January 6)
/ Also visit http://www.povrayusers.org

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I would like to add something to Chris' comments:

  The advantage of the PCM and mesh2 formats over a zipped mesh format is
that the formers can be directly read from the file itself.
  In order to read a mesh inside a zip file you would have to first
decompress the zip file. This is even worse than just having the uncompressed
version: You don't only have the uncompressed version of the mesh, but you
also have the zipped version, thus requiring more disk space.
  With the PCM/mesh2 format you don't need any extra disk space since you
can directly read the file into povray (with a macro in the first case
and directly in the second case).

  The advantage of mesh2 over PCM is that reading a mesh2 is a lot faster
(it's even faster than reading a mesh).
  The advantage of the PCM format is that you get extra functionality
(such as those mentioned by Chris).

-- 
char*i="b[7FK@`3NB6>B:b3O6>:B:b3O6><`3:;8:6f733:>::b?7B>:>^B>C73;S1";
main(_,c,m){for(m=32;c=*i++-49;c&m?puts(""):m)for(_=(
c/4)&7;putchar(m),_--?m:(_=(1<<(c&3))-1,(m^=3)&3););}    /*- Warp -*/

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Rune <run### [at] inamecom> wrote:
: My idea is to create a new format that combines the best from PCM and mesh2.

  We have been planning for an extended PCM format which will support
uv-mapping and per-triangle/per-vertex texturing (and even texture definitions
inside the PCM file).
  The format is quite finished, but I have been "coding" support for it into
the compressor for the last half year (that is, I haven't done anything ;) ).

-- 
char*i="b[7FK@`3NB6>B:b3O6>:B:b3O6><`3:;8:6f733:>::b?7B>:>^B>C73;S1";
main(_,c,m){for(m=32;c=*i++-49;c&m?puts(""):m)for(_=(
c/4)&7;putchar(m),_--?m:(_=(1<<(c&3))-1,(m^=3)&3););}    /*- Warp -*/

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Josh English <eng### [at] spiritonecom> wrote:
: Mesh
: Compression, as I understand it, determines if a mesh has useless triangle and
: removes them from the mesh, replacing them with larger triangles that fit the
: job.

  My compressor doesn't do this (you'll have to use a SSS variant if you
want that functionality). It just writes a mesh in a more compact format,
that's it. It preserves all the triangles (well, it can remove degenerate
triangles if asked).

-- 
char*i="b[7FK@`3NB6>B:b3O6>:B:b3O6><`3:;8:6f733:>::b?7B>:>^B>C73;S1";
main(_,c,m){for(m=32;c=*i++-49;c&m?puts(""):m)for(_=(
c/4)&7;putchar(m),_--?m:(_=(1<<(c&3))-1,(m^=3)&3););}    /*- Warp -*/

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