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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