Jumping in Headfirst, with Both Feet - Introducing Maya 2011 - page 63

created the mars_moon_orbit and mars_moon2_orbit nodes, and placed their pivot
points at the center of Mars to animate their orbits around Mars.
Mars is spinning on its own pivot point, but it needed another pivot point to be able
to orbit the Sun. Because you had to make the moons go with it around the Sun, you
selected Mars, mars_moon_orbit, and mars_moon2_orbit (the top nodes of the moons
that circle the planet Mars) and grouped them all together, placing that pivot point at the
center of the Sun. You called this node Mars_Orbit. This is the parent node because it's
the topmost node for this group. Wherever this parent node goes, the child nodes that are
under it will follow.
Hierarchies such as this are a cornerstone of Maya animation. It's imperative that
you're comfortable with how they work and how to work with them. If you find yourself
scratching your head even a little, try the exercise again. A proper foundation is critical.
Remember, this learning 3D thing isn't easy, but patience and repetition help a lot.
Correcting Hierarchy Problems Using the Outliner
One of the most common problems you'll run into with this project is a planet revolv-
ing around the Sun without its moon. To illustrate how to fix it using the Outliner, as
opposed to undoing and redoing it as suggested earlier, the following steps will force you
to make this error with Pluto. Usually, people learn more from mistakes than from doing
things correctly.
Go to Pluto, start the same animation procedure as outlined earlier, and then follow
these steps to force an error:
1. Create Pluto's own self-rotation by spinning it around itself and keyframing as
before.
2. Do the same for Pluto's moon's rotation.
3. Group the moon to itself, and grid-snap the pivot point at the center of Pluto to cre-
ate the moon's orbit of Pluto.
When Pluto's moon (pluto_moon) is orbiting Pluto, you're ready to group the moon's
orbit and Pluto together to create an orbit of the Sun for both.
4. Here is where you make your mistake. In Object mode, select the sphere for Pluto's
moon, and select the sphere for Pluto. Your error is that you're remaining in Object
mode instead of switching to Hierarchy mode.
5. Choose Edit ➔ Group to group them together, and call that new node Pluto_Orbit
(following the naming convention you used for the others).
6. Animate Pluto_Orbit revolving around the Sun.
7. Play back the animation.