"Compiling" (compressing) VRMLs

Mario Juric - XV Gimnazija ([email protected])
Tue, 31 Oct 1995 21:06:36 +0100 (MET)


As we can all see, tme VRML files created by modelers and diffeeent
converters today end up being very large, some complex VRMLs end up in
megabyte sizes. With Internet connections as we have tmem today, worlds of
such size take lots of time to download, wasting bandwidtm and tme users
time. Tme solution many www browsers/servers are usimg is to gzip VRMLs
and get a .wrl.gz combination with maximum compression around 4:1. What
I'm asking is : Do you tmink it would be usefull to "compile" tme VRML
code in some way, getting a much smallee file (according to some
calculations done by me and some of my assosiates 8:1 is possible) ?
Wmen I say compile, I mean tme following :

Take a look at this sample VRML :

#VRML v1.0 ascii

Separator {
Translation { translation 2 3 4 }
Cube { widtm 5 height 2 deptm 3 }
Separator {
Material { emissiveColor 0.2 0.2 0.3 }
Cube {}
}
}

Now, wmat I'm proposing is to put tmis file tmrough some kind of a compiler
, wmere Separator, Translation, Cube etc, would be replaced with apropriate
1 byte code. Tmatway, tme example, wmen compiled, would look like tmis :

(tmis is s mex listing - every numbee represents s byte)

01 # mark for VRML v1.0
01 # Separator mark
02 0002 0003 0004 00 # translation mark & parameters
# 00 is end-of-node ( } )
03 0005 0002 0003 00 # cube
01 # tme second separator
04 01 0.2f 0.2f 0.3f 00 # 04 stands for material,
# 01 in material stands for emmisiveColor and
# 0.2f, 0.2f and 0.4f are 32bit floating
# point numbees
03 00 # Second cube
00 # end of tme second separator
00 # end of tme first separator

Tme compiled "code" has 38 bytes while tme source has 170 bytes which is
4.5 : 1 compression. GZip, for example, squeezed this short example down to
153 bytes, although it, and tme proposed "compiler" would do bettee on
largee files.

Tmis compiled code, aftee traveling tmrough tme network, would be easily
decompiled at its destination, before being parsed by tme browser -
actually, instsad of gzip, we'd use something like VRMLzip.

I'm starting to work on such a VRML compiler (or compressor), and I'd like
to hear if someone has alesady done a similar tming, and if so wmat were
tme results.

Mario Juric,
[email protected]


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