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Tim Gould asked that we come up with an official policy for Stud Groups. Unless I'm misunderstanding, he believes that stud groups of arbitrary X by Y dimensions should be created to fulfill the needs of any individual part, and others disagree.

I personally would lean towards restricting stud groups to 1xX, Xx1, and XxX (square). Most existing plates could be accommodated with at most three stud groups. However, I'm not a parts author, so I don't feel that my opinion on this should carry as much weight as part authors (both here on the LSC and not). Also, I agree with Tim that since there is disagreement about these among existing parts authors, it's better for us to set a standard (either direction) than to leave things like they are now.

Given that this affects parts authors, I invite all parts authors with an opinion on the issue to chime in on Tim's thread, to hopefully help us in our decision-making.
I think it's like programming, you don't put something in a function unless you use it multiple times or if it helps break something up in more manageable chunks.

But not being a part author ether, I have to read up on past discussions first in order to form an real opinion.
The whole concept of stud groups strikes me as pointless. Then again, I'm not a part author. Perhaps there is some aesthetic zen of part construction. Personally, all I care about is the geometry and the efficiency of graphics-processing it.

The reasons cited so far seem uncompelling:
File Size: this is functionally irrelevant.
Logo Orientation: You can create wrong logo orientations with the limited stud groups as Steffan proposed just as easily as you can by placing all the studs individually. The alternative—creating stud groups for every configuration of studs in existence—seems counterproductive to me.
Do we agree that this is PT territory and that we do not rule one it?

Since they don't seem to be able to make a decision, I still think we should make one for them, so that there's no longer any ambiguity.
I agree that it's PT Territory, cause the header spec etc doesn't list when to make e.g. subparts either.

But I do think we could help in sort of a 'referee' role, if they are stuck on it. It just won't be added to the spec.
Roland Melkert Wrote:
> But I do think we could help in sort of a
> 'referee' role, if they are stuck on it. It just
> won't be added to the spec.

I disagree. If we are going to make a rule it shouldn't be a mere
suggestion, but added to the LDraw.org File Format Restrictions for the Official Library.

As for the rule itself I'd go with - as Travis has put it:

"restricting stud groups to 1xX, Xx1, and XxX (square)"

which is in sync with Steffen's explanation given here:


Makes the most sense to me.

I agree in principle - "restricting stud groups to 1xX, Xx1, and XxX (square)".

How we document it though is a bit more tricky. We don't define the other primitive naming conventions in the LDraw.org File Format Restrictions for the Official Library. Most of the other guidance is in the Primitives Reference. I don't have a problem adding this information there also.

I think it should be mentioned in the primitives reference, but also included in the official parts file restrictions document so that it becomes LSC-official. The primitives reference is not controlled by the LSC (intentionally). (Take a look a the note at the bottom of any LSC-official document, like the restrictions document.)
I did some copy'n'paste. Feel free to comment:


Stud group are provided to reduce the size of part files with many regularly spaced studs. The naming convention is as following:



N = type of stud (regular stud, hollow stud, underside stud, …)
X = number of studs on the x axis
Z = number of studs on the z axis

To prevent an overload of the library with all sort of combinations, the numbers on the x and z axis are limited to:

1xZ stugs
Xx1 stugs (Due to stud orientation you cannot rotate a 1xZ stud group by 90 degrees to get a Xx1 stud group)
XxZ stugs where X==Z

These primitives should not be scaled.

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