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Full Version: Wheel+Tyre Shortcuts: to have or not to have?
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I have just recently added some Wheel+Tyre Assembly Shortcuts to the PT.

http://www.ldraw.org/cgi-bin/ptdetail.cg...482c01.dat
http://www.ldraw.org/cgi-bin/ptdetail.cg...482c02.dat
http://www.ldraw.org/cgi-bin/ptdetail.cg...996c01.dat
http://www.ldraw.org/cgi-bin/ptdetail.cg...695c01.dat
http://www.ldraw.org/cgi-bin/ptdetail.cg...245c02.dat
http://www.ldraw.org/cgi-bin/ptdetail.cg...715c01.dat
http://www.ldraw.org/cgi-bin/ptdetail.cg...039c01.dat
and
http://www.ldraw.org/cgi-bin/ptdetail.cg...27ac01.dat
, which has sparked this discussion:

Magnus questions if having these makes sense.

I'd like to answer that question with my reasoning here.

The reason behind creating these shortcuts was that when building models,
I again and again found myself in 2 actions:

(a) searching the matching tyre for a wheel (because in MLCad all parts get scaled in the parts library preview, so all wheels and tyres look the same size)

(b) after I had found them, I to each model added a "wheel+tyre" assembly submodel

After having done this some times, I was asking myself why the assembly of (b)
was not part of the library.
Of course, the answer is: avoid clutter. As some wheels can carry different tyres, a combinatoric explosion
might occur. This prevented me some time from creating these shortcuts.
I then discovered that e.g. SR3DBuilder contains a separate database for this purpose: "TireManager.txt" (see attachment).
It is a simple text file which lists wheels plus their matching tyres.
When I saw that, I felt reminded of the discussion about 2 other things:
(i) alias part numbers
(ii) physical color shortcuts
There, the discussion was just the same: should we track this data somewhere?
The discussion about these 2 mainly went like this at those times:
First, an agreement was achieved that this information is quite valuable and needs to be stored somewhere.
The initial idea then was to have a separate database.
It then turned out that that separate database was nothing else than simple redirections
of part number to other part numbers, or of part numbers plus a certain color to other part numbers.
Then the question arose why we would create all the effort to maintain tooling etc. for a separate database,
when the existing mechanisms (i.e., LDRAW lines of type "1", part usage) would do everything we need.
Voila, a prefix was added to easily distinguish these files, and later, even an !LDRAW_ORG header type was added
(which I consider even better), and that was it. I find this solution very elegant, as it is self-contained and does
not add a secondary database.
When I remembered that, I felt that at least for the "usual" wheel+tyre assemblies, i.e., such that occur
in official LEGO models, we should have these shortcuts, basically for the same reasoning:
there is only a limited number of combinations possible, and that number is not too high:
SR3DBuilder's text file for example currently counts 165 such combinations.
Another disadvantage of that file is that it only lists matching part numbers, but it does not carry
information about the offset and orientation, and the color of the tyre. In fact, that text file is a stripped-down
instance of an LDRAW line type "1" (part usage), but without positioning, matrix and coloring element.
I felt that being a loss, and a step backward behind what our library already can do.
And I felt that these combinations should not be a private detail of tool SR3DBuilder, but of the library itself.
I cannot really see the "clutter" argument, as the number of these assemblies will be small, compared
to the plenty of physical color shortcut files we already have.

To make a long story short:
I would very much like to have these shortcuts in our library, at least for the wheel+tyre combinations
that occured in official LEGO models.

I'd like to hear your thoughts on this.
There are already many possibilities to find matching parts, so I see no real benefit for shortcuts.
Also, when I do a part inventory of a model in order buy the parts to build it in real life, the wheel and the tyre need to be listed separately.
I think this is more of a connection information (LCD) issue.

Another reason to start getting serious about official connection information.
Steffen Wrote:I have just recently added some Wheel+Tyre Assembly Shortcuts to the PT.
<snip>
I'd like to hear your thoughts on this.

To those who aren't sure this idea was necessary...

What do you feel about any such combinations that TLG counted as a single entity? Would you want/favor those being in the official library?

-- joshua
If one views the LDraw library as an inventory, yes. But maybe these belong in another class of files identified by a new !LDRAW_ORG file type.

As a CAD resource, I'm not so sure they are needed.

Personally, I think they should be included.
I think that the common shortcuts are a good thing.
Might not want to go crazy on all the possibilities, but at least the combinations that end up staying as one piece.
A few months ago, I had a bout of nostalgia, and made a bunch of models from the early '70s
I used a sub-file with this combination in almost all of them.

1 16 0 0 0 1 0 0 0 1 0 0 0 1 3137c01.dat
1 256 31 22 0 1 0 0 0 1 0 0 0 1 3139.dat
1 256 -31 22 0 1 0 0 0 1 0 0 0 1 3139.dat

Inventory generators can be updated to optionally recurse on dat files that are shortcuts using the file type.
As a result of this thread I was thinking about adding a 'related' feature to LDCad at some point.

Biggest problem with such a feature would be the information needed, so if anybody wants to take a go on compiling a list of related parts it would be a great help.

All is needed is simple lines in the form of (using names instead of numbers per example):

wheel10mm.dat tyreA10mm.dat tyreB10mm.dat

or even

leftWing3x8.dat rightWing3x8.dat

I could then convert such a list into a cross referenced internal format, and use it to populate the partbin based on the current selected part.
Bricklink has a lot of that info - BrickLink Catalog Item Relationships.
It would need to be mined, I didn't see the match data in the available downloads.
I suggest to not use a new text file format for that purpose.
The existing LDRAW format can combine two parts easily
AND position them correctly relative to one another:
1 16 ... ............ part1.dat
1 16 ... ............ part2.dat
That is what the shortcuts do.
As said, the issue is analogous to the physical color shortcuts:
there, instead of inventing a secondary database or format, we used the existing technique.
I like that approach of "keep it simple".
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