Subject:
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Re: Movement and friction
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Newsgroups:
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lugnet.cad.dev.lcd
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Date:
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Mon, 11 Feb 2002 22:33:43 GMT
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Viewed:
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2942 times
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I haven't commented substantially on LCD, so maybe I should.
I am contemplating an algorithm that will find all of the possible
stud-insertion points on a part. The obvious way to do this is to recognize
the tube or enclosing box with their well-understood properties. The more
fundamental thing is to discover an opening where a stud makes at least 3
points of contact. Of course this is only for a stud and tube coupling.
(Each tube probably has 1, 2 or 5 possibilities.)
Second, how is this information to be used by a modeling program. (Either it
is loaded from the part file, or generated in memory from the algorithm.)
The obvious approach is that the program stores knowledge of point and
approach vector for each connection point, and checks for approximate
matches between a moving part and nearby candidates.
To find nearby candidates, BrickDraw3D for example maintains a list of all
parts sorted by height. A range query returns all parts intersecting a
bounding box . For instance, the bounding box of a moving part, usually
excluding the part's studs, or a bounding box + 1 cell width.) (range query
is as described in Franco Preparata, _Computational Geometry_, 1987.
These are my thoughts on how to proceed:
For each closest pair of plane surfaces that are parallel, each pair of
connection points within the planes are checked for nearness. Visual
feedback will be provided as they become close. If the part is let go it can
be moved to the exact point of connection, this is usually called
snap-to-grid (but the connection point may not be a grid cell.)
It is possible that some connection points should be denied access. For
example when trying to plug a 1x2 brick stud into a tube of a 2x2 brick.
This can be checked for, Here, the 1x2 brick has unsatisfied connection
points (studs) which intersect the bounding box of the other brick, a clear
violation.
I apologize in advance for not using the proposed terminology for every concept.
-Erik
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Message is in Reply To:
 | | Re: Movement and friction
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| (...) For the time being, Barney, the problem is that if we will have a database at all. Lugnet.CAD.Dev was very enthusiastic when we presented the idea. All wonders endure three days, this was the very example, after the three days came silence. (...) (23 years ago, 11-Feb-02, to lugnet.cad.dev.lcd)
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