Subject:
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Re: Backwards Compatibility (Was Calling all Meta-commands)
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Newsgroups:
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lugnet.cad.dev
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Date:
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Thu, 20 Mar 2003 00:01:15 GMT
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Viewed:
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1942 times
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In lugnet.cad.dev, Travis Cobbs writes:
> Here is my suggestion (just a suggestion, mind you). All future
> meta-commands could look like the following:
>
> 0 {META} <command> [arguments]
I like that. I think a clear indication that a comment is in fact a meta statement is needed.
And I find "0 {META} " more distinct than (META), <META>, {BFC}, <BFC>, MODULENAME
and whatever else has been suggested.
But we're still stuck with the already adopted meta commands,
so "0 {META} " would be for new ones.
> Another note: I haven't really seen it in this thread, but there is a
> fundamental difference between meta-commands that actually cause behavior,
> and formalized tags for file meta-data. For example, "0 Author:" is a
> formalized tag for specifying meta-data. Programs may want to parse the
> data, but it's still just a tag.
Why do you think there is a fundamental difference?
Isn't it just a matter of how the meta command/tag is interpreted?
About backward compatibility, is LDRAW.EXE the ultimate test?
BFC is truely backward compatible, a BFC'ed file will render correctly in LDRAW.
"0 FILE" is backward compatible in the sense, that it is a zipping format.
An MPD file can be unpacked into separate files, and it will render correctly in LDRAW.
A program that can directly import an MPD file is just a convenience (a good one that is),
but comparable to e.g. a compiler that could compile files in a .zip file.
Likewise TRANSLATE/ROTATE/SCALE/TRANSFORM are only backward compatible
if first converted (inlined) by ldlite -R into an ordinary LDRAW format file.
Another issue I don't think has been discussed is extended colors (direct colors),
see http://www.hassings.dk/l3/l3p.html#extcol
They are supported by (at least) ldlite, ldglite, MLCad, LDView and L3P/L3Lab.
But they are NOT compatible with LDRAW.EXE, which will render incorrect colors.
If they were to be compatible, the syntax should have been e.g.
0 NEXTCOLOR 0x2RRGGBB
and the following line should use the nearest LDRAW color.
(and if the nearest color was a dithered color, it should be put into a subfile!)
/Lars
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