Slope variations 92946 vs 15672

[Merlijn Wissink]

Yesterday, an interesting story was posted on the Rebrickable blog.
It's about two minor slope variations (92946 and 15672) which actually does have a (relatively) 'major' impact on the way the piece can be used.

I was wondering, does the LDraw library included such minor variations? I guess the answer is yes, since the library also includes other mold variations. But, this one is so minor, almost unoticeable on a PC screen.

Aside from that, it does mean that our current 92946 is actually slightly wrong. At the moment, the slope is exactly the same as 3040b, which it shouldn't be according to the measurements (and even LDD, as stated in the post).

Any thoughts about this?

EDIT: I forgot a link (for the lazy people around here : http://rebrickable.com/blog/2016/mysterious-slope

[Philippe Hurbain]

Unfortunately the Rebrickable paper does'nt seem available at the moment... but anyway I am sorry to tell you that you are moving in a mine field here
LDraw slopes are kind of wrong since the beginning, they were modeled with a foot that is 4 ldu tall, while real value is closer to 5. And to keep compatibility all new parts are made to fit older ones... and are wrong too.

[Merlijn Wissink]

It works (now) for me. I forgot a link anyway: http://rebrickable.com/blog/2016/mysterious-slope

Why were the feet made 4 ldu? Just a measuring 'error' in the beginning?
In any case, why isn't it fixed instead of keep using the wrong size? I mean, it's not going to create any issues in past models, right?

[Philippe Hurbain]

It works (now) for me. I forgot a link anyway: http://rebrickable.com/blog/2016/mysterious-slope

Not the first time I have problem accessing rebrickable. Maybe something specific here (still doesn't work now)

Why were the feet made 4 ldu? Just a measuring 'error' in the beginning?

Yup. Dates back to initial LDraw DOS version by James...

In any case, why isn't it fixed instead of keep using the wrong size? I mean, it's not going to create any issues in past models, right?

Sheer amount of work (which gets worse and worse at time passes...) and need to synchronize all updated parts release to avoid weird looking models with a mix of old and corrected slopes.

[Merlijn Wissink]

It's coming up at the part tracker:
http://www.ldraw.org/cgi-bin/ptdetail.cg.../15672.dat

I think it's best to fix all other slopes (what Philo was talking about). Altough I'm not too knowledgeable about part creation, it can't be that difficult right? Just editing a few vertices. Or am I overlooking something?

[Philippe Hurbain]

Believe me, it's a HUGE work. Granted, for simple slopes it's obvious. Then you get patterned slopes. Then curved slopes and wedges. Then slopes with hinges. Then...
If it was simple it would have been done for a while!

[Merlijn Wissink]

I thought it was only about the normal slopes. Well, then yes, it does indeed sound like a lot of work. Yuck