Subject:
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Re: open source ldd?
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Newsgroups:
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lugnet.cad.ldd
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Date:
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Sat, 19 May 2007 05:57:16 GMT
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Viewed:
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27933 times
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In lugnet.cad.ldd, Don Heyse wrote:
> In lugnet.cad.ldd, Travis Cobbs wrote:
> > do you know of any open source cross-platform libraries
> > for in-memory zip handling and for XML parsing?
>
> How about zziplib (or just zopen) and tinyxml?
Thanks for the tip. I'll take a look. I'll have to do some testing with
zziplib to see if it will work with the ldraw.org zip files. It doesn't support
all zip compression schemes, but I suspect it will work.
If I need XML parsing, I'll take a look at tinyxml.
I glanced at the db.lif file (which I believe contains all the geometry data for
the parts for LDD), and came to the conclusion that I don't really want to
attempt to reverse engineer it. It's binary, and 9+ MB big. It appears that
the .lif format is one created by Lego as a generic container for other files
(similar to tar). I wasn't able to find any documentation on the net about its
actual format, although looking at the files makes it appear that I could decode
that level enough to get back the original files that are archived inside (it's
not compressed).
But since the actual geometry data is binary, reverse engineering that could
prove a lot more difficult, and I'm not really into that kind of thing. There's
actually an lxf viewer on sourceforge (written in Java, and not updated in over
a year, so supporting an earlier lxf format). However, it doesn't even try to
use LEGO's geometry data. The project itself includes a small library of parts
in its own format written in XML. The good thing is of course that the LDD
geometry data file isn't needed for the viewer to work. The bad thing is that
there's a serious shortage of parts. LDView would of course be better off just
using the ldraw.xml file to do the conversion, but LDD 2.0 and 2.1 come with an
ldraw.xml file that's pretty much empty, and I'm not going to be the one to fill
it in.
One final thing. Unless US law exempts me from that clause, the fact that I've
installed LDD 2.1 (and agreed to the license agreement) means that I agreed not
to reverse engineer it. While you could argue that reverse engineering lxf
files is still ok (since they are created by the software, and not actually part
of the software), the geometry data file is definitely part of the software.
And unlike the lxf files, which are easy to understand, db.lif is definitely not
designed to be understood by a human.
So it seems that the only way LDView would get native LXF support would be if
ldraw.xml were brought up to a useful status. But since that should in theory
allow for proper exporting of LXF files from LDD, it doesn't seem to be all that
useful of a feature to add to LDView.
--Travis
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Message has 1 Reply:
 | | Re: open source ldd?
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| (...) I spent a couple evenings looking over this when it was first released. For a proprietary format, it's nicely straightforward (the widespread use of XML lately helps, of course). (...) Interestingly, 2.0 contained more information in than 2.1 (...) (17 years ago, 21-May-07, to lugnet.cad.ldd)
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