Subject:
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Re: MLCad rotaton point?
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Newsgroups:
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lugnet.cad.mlcad
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Date:
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Sun, 2 Oct 2011 16:40:40 GMT
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Viewed:
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23203 times
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In lugnet.cad.mlcad, Dave Schuler wrote:
> Just getting my feet wet on MLCad @ long last, and one thing that's giving me
> trouble is the rotation of parts. I got to be quite good at manipulating
> parts in LEdit, but I can't seem to rotate them at all in MLCad. At least,
> not in any way that yields a result resembling what I had in mind.
Okay, in MLCad (and possibly other LDraw GUIs), an individual part will rotate
around its origin point. On any standard brick/plate/tile, this origin point is
typically found in the exact center of the top surface, excluding any studs. So
if you copy/paste one tile into the same space as the original copy, then flip
one of them upside-down, the flipped one will be resting top-to-top on the first
tile. Same for plates and bricks, except the studs will all be buried inside
the other part if you do this.
Grouped parts get a little goofy. If you select multiple parts and then rotate
them, the first part you selected will determine the rotation point for the
entire cluster. If you select multiple parts, then group them, and then rotate
them immediately, the first part will still determine the rotation point. If
you select multiple parts that are already in a Group, I think it uses the
origin points of all involved parts to determine the rotation point for the
group, which is pretty useless. So, if you want to rotate an existing group,
the best way to do it is put a dummy part in there that lines up with the
rotation axis so you can select that part first, then CTRL-select the group, and
then rotate the dummy part and the group together.
Now, the tutorial that was linked in the previous reply suggests using the
three-axis rotation "element", but I've found that to be too cumbersome to use
in a quick and effective manner, partly because it's tricky to line up properly,
and partly because you would ideally need to bury it inside of the cluster of
parts you want to rotate. What I do instead is use the lightsaber blade to
rotate parts on click hinges, finger hinges, and anything that has a
bar-thickness rotation surface (1x2 hinge bricks, minifig equipment, etc.). For
rotating parts around a stud connection, I use 1x1 round plates. The reason I
do this is it's very easy to line up the bar and stud shapes with like elements,
so I know my rotation axis is dead on every time. I also move the dummy
rotation element will outside of the model, so I can' select it in the view
panes instead of having to scroll through a few hundred, or even a few thousand
elements in the text box. I will also change rotation pieces to odd colors so
they're easy to spot if I forget to delete them before I generate a parts list.
If I'm building a red model, and I end up with a green lightsaber blade in the
list, I clearly don't need it to build a physical copy of the model.
When you want to rotate a cluster of parts, it's always a good idea to use the
Group function on them so you don't risk grabbing a part you didn't want, or
missing one that you did want. Doing this can take some time to set up, but it
does allow you to do really complex rotation tricks, like stringing a bunch of
rotated part clusters together. For instance, I built a spider mech once, and
each leg is sticks out at an angle from the body using a vertical axis, then has
3 joints on horizontal axes for a combined total of 32 rotation points on the
entire set of legs (plus one for the cockpit canopy, and another one for the
middle of the body). When I made the original LDraw file, I had no clue how to
rotate groups effectively, so I was adding individual parts, rotating them to
the approximate desired angle, and then moving them as close as I could get to
lining up with the intended attachment point. Some I was pretty close on, and
others I could never get quite right. This whole process also took me at least
one full evening to finish. Once I figured out how to force a rotation point
for a group of parts, I went in and cleaned everything up in a couple hours. It
would have been even faster if I'd done it the first time, since I wouldn't have
had to unrotate all the parts in the original version of the file.
As far as settings go on the MLCad interface (Settings, General, Change, and
then the Step/Snap/Grid tab), what I do is use the standard settings for the
Coarse group (10/8/10/90) because they're the most useful numbers for doing
quick and dirty part assembly with bricks, plates, and tiles. For the Medium
setting, I use 5/4/5 for the part movement, because that's useful for doing
stuff like attaching things to jumper plates or face-up brackets. The angle I
use is 22.5, because that's exactly how many degrees the click hinges and that
half-degree is a PITA to deal with if all three of your rotation degree settings
are in whole numbers. For the Fine settings, I go with a straight 1/1/1/1.
This allows for more precise placement without making you deal with garbage
settings. No standard part dimension should force you to use anything less than
that to move it around on a right-angle grid, and that 1 degree rotation allows
you to get almost any angle you'd desire without taking forever to process. On
the rare occassion when I need to make use of a half-degree rotation for
whatever reason, rather than digging into the menu system to change one of those
settings, I just use a combination of the 22.5 and 1 degree rotations to get
what I need. So if I need it to be 15.5 degrees off a right angle, I rotate it
22.5 in one direction, and then 7x1 in the other in about the about the time it
would take to change the settings the first time, without any need to go back in
and change them back. Anything smaller than half a degree has never been
significant enough that to notice on any model I've designed. but if I ever
really do find a need to do 1/10 degrees or some other weird number (rotating a
really long section, like the center lines on some of the UCS Star Wars sets
might require this to get them to line up properly at both ends), I can always
tweak my settings as needed, but as long as I'm not having to make any changes
to the settings on a regular basis it's far simpler to just work with a standard
set that covers as many issues as possible.
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Message is in Reply To:
 | | MLCad rotaton point?
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| Just getting my feet wet on MLCad @ long last, and one thing that's giving me trouble is the rotation of parts. I got to be quite good at manipulating parts in LEdit, but I can't seem to rotate them at all in MLCad. At least, not in any way that (...) (13 years ago, 3-Sep-11, to lugnet.cad.mlcad)
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