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 20:06:23 GMT
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Viewed:
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10632 times
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In lugnet.cad.mlcad, Timothy Gould wrote:
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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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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 MLCad, and I still use Blender for
handling animations.
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Message has 1 Reply:
 | | Re: What about a LEGO TECHNIC tutorial
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| (...) Yeah, that would be great although you usually have to enter angles manually most of the time. What would be even cooler was custom grid buttons: So I don't have to change the default grid values each time I swich from working with models to (...) (19 years ago, 8-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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| (...) 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 (...) (19 years ago, 7-Jun-05, to lugnet.cad.mlcad, FTX)
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