#Linking with a path ???
6 messages in this thread
I'm new to 3DS, so please forgive the ignorance. I'm trying to animate the
moon orbiting the earth, while the earth is orbiting the sun. I place all
three objects in position in the 3D Editor. I create a large ellipse in
the 2D Shaper and assign it as a path in the Keyframer to the earth. I
create a smaller ellipse in the 2D Shaper and assign it as a path in the
Keyframer to the moon. I then link the moon to the earth, but when I do
this I screw up the earth's path around the sun. I want the moon to follow
an ellipse around the earth, which is following an ellipse around the sun.
Can I do this? How?
Thanks for the help.
Dirk
Good question, Dirk (and a common one, at that). Here's how to do compound
rotations to simulate multi-body orbital motion:
1) Make a dummy object inside the sun and link the earth to it.
2) Make a dummy object inside the earth and link the moon to it.
3) Link the dummy object inside the earth to the earth.
4) Link the dummy object inside the sun to the sun (this step is optional,
unless you plan on moving the sun around and want the rest of the bodies to
move with it).
Now, you can rotate the moon by itself, and rotate the moon's parent (the
dummy object inside the earth) to get the moon rotating around the earth.
Use the same technique for the earth, and voila!
Have fun,
– G
PS: The dummy objects don't _have_ to be inside their parent objects. If
you want to hit them with the mouse, you might want to make them slightly
larger than their parents. But if you want to use the H-key to select
them, you can stow them inside their parents to get them out of the way.
Gary,
Thank you, thank you, thank you! You've just saved me countless hours of
trying to figure out how to do multi-body orbital motion. And being the
3DS neophyte that I am, I might not have figured out how to do it any time
soon. Thank you for having the ASOFT forum and for being such an active,
responsive group. I love your product.
Dirk
P.S. I just finished the 14 regular tutorials and the 1st new features
tutorial. Hope to finish the rest of the 7 new features tutorials by the
end of the weekend. They are *great*. Some of the best computer tutorials
I've ever used. I just wasn't quite bright enough to pick up the use of
dummy objects for orbital simulation. Thanks again!
I'm not clear on the "why" of this. It sounds a lot like the question I
had on "pendulum", where I needed to perform the link before assigning
rotation. What are the dummy objects for?
Humbly confused, LAM
The dummy objects supply an independent coordinate systems and pivot point.
If you want the moon to rotate about its own center AND the center of the
earth, that requires two different rotational systems… easily provided by
adding a dummy object.
– G
Ahhh.. Light bulb lights. Thanx, LAM