Path: utzoo!utgpu!news-server.csri.toronto.edu!mailrus!cornell!uw-beaver!ssc-vax!voodoo!stu
From: stu@voodoo.UUCP (Stuart Liddle)
Newsgroups: comp.graphics
Subject: Re: anything to DXF format as used by AutoCad
Message-ID: <972@voodoo.UUCP>
Date: 10 Jul 90 15:17:05 GMT
References: <1990Jun28.143847.9013@gpu.utcs.utoronto.ca> <1126@kirk.nmg.bu.oz>
Reply-To: stu@voodoo.UUCP (Stuart Liddle)
Organization: Voodoo Graphics Project
Lines: 66


In article <1126@kirk.nmg.bu.oz> you write:
>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
                                    ^^^^^^^^^^^^ 
  Yes, what you said is true, AutoCAD is vector based, however what you stated
earlier about it not being object-oriented is not quite true.  I believe you 
are confusing a graphic term with an Object Oriented Programming(OOP) term.

In several graphic packages (AutoCAD for instance), an object refers to a 
set of graphics primitives that have been "grouped" together to form a single
OBJECT.  This object can then be selected and manipulated as a whole rather
than having to manipulate the individual line-segments that makes up that whole.
This makes it easy to have a template of architectural objects, such as 
bathroom fixtures (sinks, toilets, etc.) that can be added to or moved around
in a drawing.

>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...

 I would call this a graphic primitive.

>
>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...

 This sounds pretty interesting, but it is really quite different from what
AutoCAD (and others) is talking about.
>
>
>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
                      ^^^^^^^^^^^^^^^^^^^^^^^^^^^
 I would like to know about these!  Tell me more.

>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.

 I don't know precisely that Autodesk calls AutoCAD an "object-oriented" CAD
system.  But, if they do they are referring to the kinds of objects I mentioned
above and the people who know about CAD and vector-based graphics packages 
probably would not be confused with the OOP term.

Just my (U.S.) $0.02 worth.

---------
Stuart Liddle                             (206) 234-2558 (wk)
Boeing Computer Services     ....uw-beaver!ssc-vax!voodoo!stu  
M/S 6M-17,     P.O. Box 24346,      Seattle, WA    98124-0346
* "I do not know what I do not know." - Alan Arkin, (movie unknown) 
* "You can never turn your back on your face."
* "How can you be in two places at once, when you're not anywhere at all."