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Subject: 
Is there an origin point specified in LDRAW parts?
Newsgroups: 
lugnet.cad
Date: 
Wed, 25 Mar 2009 06:35:39 GMT
Viewed: 
9753 times
  
If there is an origin point specified in LDRAW part files, I would like to
know what is needed in order to calculate it's position and alignment to the
x, y, z coordinate system LDRAW uses.

Can anyone point me to where I can find information that would be useful in
retrieving the origin point of a LDRAW part, and how for simple parts like
bricks this could be used to determine the extent of the x, y, z space that
the part would take up for rectangular parts like bricks?

Are there any utilities available that would show origin points in parts,
and how they are calculated, and for parts with multiple studs EG 2x4 brick
where the stud connections would normally be situated?

I was assuming that for every part, like bricks, that the origin point would
be at some naturally-occurring connection point like a stud or hole.  But it
would seem that this is not always the case, and one document said that the
parts are always centered on a centre point which the rest of the part would
be drawn from.

It appears that for the most part, LDRAW model files rely on the user being
able to properly position the parts on standard values and that there's no
way of specifying alignment for studs, to describe bricks that would be
stacked on top of each other physically, for example.

I don't know if we even need such information in parts, or if there's a way
around it that would eliminate the need for an origin point.

I'm familiar with the way in which rotation matrixes work, and I can
understand that programs use this to position and rotate parts in models,
but this is not what I'm after.  What I'm after is how could the user
calculate a part's origin point themselves, should they need to do so, and
if they're reading in raw part data from a part file and not from a model?


Cheers ...

Geoffrey Hyde



Message has 2 Replies:
  Re: Is there an origin point specified in LDRAW parts?
 
(...) Well, the origin is simply the zero-point X=0;Y=0;Z=0 in all parts, no exceptions. The quads/triangles/line...itives/... are built around that origin. (15 years ago, 25-Mar-09, to lugnet.cad)
  Re: Is there an origin point specified in LDRAW parts?
 
(...) Origin of all parts is x=0,y=0,z=0. Where this origin is placed at the part is different. Y-Direction: If the part have studs, then the y=0 is the surface below the studs. If the part has no studs, then it should be at the top of the part, or (...) (15 years ago, 25-Mar-09, to lugnet.cad)

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