Subject:
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Re: What about a LEGO TECHNIC tutorial
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Newsgroups:
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lugnet.cad.mlcad
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Date:
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Tue, 7 Jun 2005 18:41:53 GMT
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Viewed:
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10543 times
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For me, the biggest issues is rotations. Technic allows for many more
orientation angles than the standard brick. Rotating about X,Y, and Z axiz
are pretty good, but I usually have to adjust the “fine” grid settings
rotation to something like 1 degree. Also I typically set the fine moement
settings much smaller than the default.
It sure would be nice to have a few more setting levels.
One problem with technic designes is that axis of rotation are often not
parallel to the X,Y or Z planes. I use GROUPS to collect all parts related to
a rotation axis, so they are easy to work with. Then I rotate them so the
rotation axis is parallel to one of the X,Y, or Z axis’. From there, I rotate
the group the amount needed. I then have to reverse the original rotations to
get the group oriented back to the original rotation axis.
It sure would be nice to be able to pick an axle or pin, and use that to
define a rotation axis. From there you could rotate the group clockwise or
counter clockwise.
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It oughtn’t be too hard to do that. You just use the pin to define your normal
vector and then just work backwards from the projection to work out the rotation
matrix. I noticed today that MLCad already seems to have a routine to calculate
these rotations. I’m guessing it is using the matrix exponential of a
cross-product (SO_3 matrix) for this.
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I spend a lot of time managing the rotation point.... being able to move it
small increments by the keyboard might help, but I’ve never studied MLCad
enough to know if it already exists.
The width and height ratio stuff that LEGO is famous for is also a problem
in technic. Getting pins and axles precisely in the holes is a tough task,
especially if the axis of the pin is not parallel to X, Y, Z.
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It would be great if you could choose to move in the current rotated basis set.
Eg. If you are moving a part with a rotation matrix 0.866 0.5 0 -0.5 0.866 0 0 0
1 then you can move in the basis set defined by (0.866,0.5,0), (-0.5,0.866,0),
(0,0,1) in unit steps (which is probably fine enough and would move you relative
to the piece you are attaching to).
Just a few thoughts...
Tim
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Message has 1 Reply:
 | | Re: What about a LEGO TECHNIC tutorial
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| (...) Admittedly, I have oft wished for the ability to create custom rotation buttons so I could make X,Y,Z buttons for 11.25,15,22.5,27.125,30 and 45 degree rotations to accomodate the rotation angles of various technic parts... But I still love (...) (19 years ago, 7-Jun-05, to lugnet.cad.mlcad, FTX)
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Message is in Reply To:
| | Re: What about a LEGO TECHNIC tutorial
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| (...) Hi Eduardo, All the models I enter are technic. Compared to brick building, technic is much harder. With the standard bricks, everthing is turned multiples of 90 degrees, and studs line up parallel to the x,y, or z axis. Jaco is right, it (...) (19 years ago, 6-Jun-05, to lugnet.cad)
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