# Sun, Earth, and Moon - 04/26/Friday timed exercise

### The hands-on quiz race to model a solar system subset... (One Star, One Planet, and One Moon only) And starring the SUN and the EARTH and the MOON!

1. Create the Sun. If necessary, Modify menu > Freeze Transformations after you have set it up (Rotated, Sized, Extruded, put in spikes, etc.) Be sure to name it SUN!

2. Duplicate the Sun. Name the copy EARTH. Be sure to have SNAP TO GRID on and position the EARTH at (n, 0, 0), i.e. with TransformX set to an integer such as 8 or 9 or 10. Resize the EARTH so it is smaller than the SUN.

3. Duplicate the EARTH. Give the duplicate copy of the EARTH the name MOON.

4. Animate the Sun to ROTATE on it's Y axis, i.e. RotateY will be keyframed to 0 at Frame #1 and keyframed to 360 or 720 at Frame #48 (or whatever frame is the last frame).

If you have any STATIC channels be sure to Edit menu > Delete by Type > Static Channels. It depends on how you set the Keyframes!

5. Repeat the above process for the Earth and the Moon. Each of the 3 actors in this Sun, Earth, and Moon drama must ROTATE on its own axis, i.e. rotate on its own default PIVOT POINT.

What has been achieved at this point? You have all three objects sized and in the proper position and animated to rotate 360 or 720 degrees around thier own axis (pivot point).

6. Next you will do the ORBITS. They will be named earthOrbit and moonOrbit.

1. Which orbit is simpler? The EARTH orbit is the simpler problem, because the SUN is positioned at (0, 0, 0) for its x, y, and z transforms. And furthermore, the SUN does NOT orbit or move in a path.

2. The MOON orbits the EARTH, but the EARTH itself is moving as it orbits the SUN.

7. Earth orbit involves the following:
```     a.  Create a GROUP consisting of just the EARTH.

Edit menu > Group command with only the Earth selected.

What is the keyboard shortcut for the Edit > Group command?

b.  Name the GROUP earthOrbit or EarthOrbit.

c.  The Pivot Point for any newly created group is at the
center of the entire 3D grid, i.e. at (0, 0, 0).

How convenient!  That is exactly where the SUN is centered.

We do NOT need to change the PIVOT POINT for the earthOrbit!

d.  Be sure to switch from Object mode selection to Hierarchy
mode selection, if needed.  H O C
(HOC is the KEY).
Note:  You can always use the OUTLINER to select objects
or to select the GROUP or entire hierarchy too.
That would be SLOWER here and not needed.

e.  Make sure the Time Slider is set to Frame #1, the beginning
of the animation.

Make sure that the Earth Orbit is the selected object.
(Not the EARTH, but the EarthOrbit, which is a Hierarchy,
i.e. the H in HOC).

f.  Press s to set the keyframe.

g.  Move to the last frame, probably Frame #48.

i.  Change the RotateY for the EarthOrbit to 360 or 720.

j.  Press s to Set the Keyframes.

k.  Now remove the Static Channels to clean it up and only
leave RotateY keyframed for the EarthOrbit.
```
8. Finally, its time for the Moon Orbit.
```     a.  Create a GROUP consisting of just the MOON.  Name it MoonOrbit.

b.  Make sure Snap to Grid is turned on.

c.  With the MoonOrbit selected (and NOT just the Moon object),
and with the Move Tool active, press the Insert key.

Drag the RED manipulator of the MoonOrbit Pivot Point until
it Snaps to the GRID point on the X axis where the Earth
is centered.

Now press the Insert key again to get out of adjust pivot point mode.

d.  With selection mode in Hierarchy mode (the H in H O C),
click on the Moon
and because you are in H Hierarchy mode
instead of O Object mode, what happens?

The MoonOrbit is selected.

e.  Hold down the SHIFT key and click the Earth.

You are still in H mode instead of the O mode of HOC, so
the EarthOrbit is added to the selection, and is the
2nd item selected.

Recall:  Click the item you want to be a CHILD first,
i.e. tap the child on the shoulder first.

Then, hold down SHIFT key and click the 2nd item,
which is who you want to be the PARENT of the
CHILD.  Shift-CLICK the parent on the shoulder 2nd.

f.  Edit menu > Parent command established the relationship of
the EarthOrbit being the parent of the MoonOrbit.

```
9. Finally, if your animation is all working okay and the Earth and Moon are together in orbit around the SUN, with the MOON orbiting the EARTH, all that is left is to FINE TUNE the animation to get rid of the EASE IN and the EASE OUT for the keyframes.

10. Window menu > Animation Editors > Graph Editor opens up the GRAPH EDITOR.
```    a.  Did you have the EarthOrbit selected?

b.  Click on the RotateY attribute name in the Graph Editor window.

c.  Type the F shortcut to Frame the selected attribute's GRAPH
and notice how it is curved as it comes out of the start
keyframe and it is curved as it arrives at the 2nd keyframe.

d.  Draw a bounding box around the keyframe at Frame #1.

Do the Tangents menu > Linear command.

e.  Repeat for the keyframe at Frame #48 (or whatever frame you
have for the end of your animation.

```
11. You should now see the nice animation without the slowing pause where it repeats. To make it perfect, set the playback end to frame #47 instead of frame #48 and watch it again.

Do this again after a break or do it again tomorrow. Does it go faster each time? Do the concepts and techniques make more sense with repetition?

## Group competition experiment during week #15? Small groups...

1. Group size - 3 or 4 students, randomly selected...

2. Fastest time by a group... Add up the times of all 3 or 4 members.

3. Fastest time by an individual...

4. Most improved group... If a 2nd attempt is made perhaps at the next class. The group that made the largest gain in speed and reducing total time.

5. Most improved individual... This would indicate the group discussion was especially valuable in increasing the skills of one student more than any other student in the entire class.

6. I wish I had thought of this idea back in January. It might be fun and could increase the rate and depth of learning concepts and mastering the basic skills. Like a game.