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From: cameron@kirk.nmg.bu.oz (Cameron Stevenson)
Newsgroups: comp.sources.wanted,alt.graphics.pixutils,comp.graphics
Subject: Re: anything to DXF format as used by AutoCad
Message-ID: <1126@kirk.nmg.bu.oz>
Date: 3 Jul 90 22:29:15 GMT
References: <1990Jun28.143847.9013@gpu.utcs.utoronto.ca>
Organization: Network Management Group, Bond University, Australia
Lines: 27

From article <1990Jun28.143847.9013@gpu.utcs.utoronto.ca>, by tj@gpu.utcs.utoronto.ca (Terry Jones):
> DXF files are object oriented. Group 3 FAX and PBM are bitmap formats.

I think it incorrect to call DXF files object-oriented. Autodesk has been
using this term for a while now to distinguish AutoCAD from painting
applications. What they SHOULD be calling AutoCAD (and what you should
therefore be calling DXF files) is vector based. As you have correctly
stated, FAX, GIF, and heaps more are bitmap (or pixel) file format - ie.
this dot is black, the next one is white, and so on...

Vector based file formats store the definition of a line (or any other
graphical element) - ie. this line starts here, is so thick, and goes there,
and so on...

Object-oriented files (or more correctly, the data created by object-oriented
systems) store both the data (ala pixel and vector files) AND some code
within the object - ie. I am a line, and when I receive a message to display
myself, I will start here, and end here, but if I recieve a message to
tell how long I am I will return a number, and so on...


Sorry to be picky, but it annoys me when Autodesk call AutoCAD an
object-oriented CAD package. It is true, there are some object-oriented
CAD packages around (most in experimental stages), but AutoCAD is NOT
one of them. The implication from Autodesk (I think!) is that AutoCAD
has something that it's competitors doesn't, and most CAD purchasers
don't know enough about the subject to question them.