Animation Tutorials > Animating with Auto Key: Bouncing Balls > Bouncing a Ball >
Use the Curve Editor to Improve the Motion

The Curve Editor is part of the Track View feature, which is a general-purpose tool for managing and adjusting animation.

Set up the scene:

- Continue from the previous lesson.

Open the Curve Editor:

- Right-click the basketball, and choose Curve Editor from the quad menu.

  3ds Max Design opens the Curve editor. The tracks you just created for the ball should be visible on the left, and the curves themselves should appear in the curve window to the right.

  TipIf the tracks and curves don’t appear when the Curve Editor opens, pan in the controller window at the left until you see the position tracks, then click and Ctrl+click to highlight them.

  The Z track, in blue, clearly shows the up-and-down movement of the ball. The X and Y tracks are both flat, which indicates no change along these axes. In fact, the ball should travel along the Y-axis, as if it were given some forward momentum when it was dropped.

  NoteThe track curves are color-coded like the axes on transform gizmos: X is red, Y is green, and Z is blue.

Change the coordinate system:

The Curve Editor displays World coordinates. By default, viewports display View coordinates.

- On the main toolbar, open the Reference Coordinate System drop-down list and choose World.
  TipWhen you work with Track View, avoid confusion by setting the reference coordinates to World so viewports and the Track View window show the same coordinates.

Add movement along the Y-axis:

1. Drag the time slider to frame 30.
2. Activate the Left viewport. Turn on (Auto Key) once again, then move the ball to the right along the Y-axis.

   The curves in the Curve Editor also update to show the change you made.

   That doesn’t look quite right: As you can see if you scrub the time slider, the ball drops vertically and then travels forward. Instead, the effect we want is a smooth forward motion, as in the diagram at the beginning of this lesson. The culprit is the Y Position key at frame 15, which pins the ball to the same Y position it has at frame 0.

3. Turn off (Auto Key).
4. In the Curve Editor, click the Y Position key, along the green curve, to select it.

   The key turns white when you select it. It also shows some tangent handles.

5. Press Delete to delete the Y Position key at frame 15.

   Now the basketball moves forward from frame 0 to frame 30, as you can see if you scrub the time slider. The animation still looks too mechanical, but you’ll improve that soon.

   NoteThe X Position track is still flat, indicating no change along that axis. You could delete all the keys in the X track without affecting the animation.

Add a trajectory and ghosting to improve animation display in the viewports:

You can display the trajectory of an object in viewports, and also “ghost” images of the moving object. Both these options help you visualize your animation.

1. In a viewport, right-click the basketball and choose Object Properties from the quad menu.

   3ds Max Design opens the Object Properties dialog.

2. In the Object Properties dialog Display Properties group, click Trajectory to turn it on, and then click OK.

   Now viewports show a red trajectory for the basketball, with white tick marks along its length. Each tick represents a frame.

   Basketball trajectory in a viewport

   The ticks are more closely spaced at the beginning and end of the trajectory (this is easiest to see in the Left viewport). This is a timing effect known as “ease in, ease out” (or “slow in and slow out”). However, the ticks are evenly spaced around frame 15, where the ball bounces off the floor. This is one reason the bounce doesn’t appear realistic, yet.

3. From the menu bar, choose Views Show Ghosting to turn it on.

   Now when you drag the time slider, viewports show ghost images of where the ball has traveled.

   The default ghosts are closely spaced, and a little hard to read. You can improve this by changing the default settings.

4. From the menu bar, choose Customize Preferences. Go to the Viewports tab.
5. In the Ghosting group, change the value of Ghosting Frames to 4 and change the value of Every Nth Frame to 2. Click OK.

   Now when you scrub the time slider you see fewer ghosts. The ghosts are spaced two frames apart. This makes it easier to see how the animation is progressing.

Adjust the timing of the bounce in the Z dimension:

1. In the Curve Editor Controller window (the list of objects and tracks at the left), click the Z Position track to display the curve for just that track.
2. Click the “floor” key at frame 15 to select it (you also can select the key by dragging a box around it).
3. On the Track View - Curve Editor toolbar, click (Set Tangents To Fast).
4. Scrub the time slider.
   NoteAs you might notice, the trajectory display in viewports doesn't update until you move the time slider.

   Now the bounce has a snap to it that makes it look more like a real bounce.

Adjust the basketball’s forward motion:

As it did for the ball’s up-and-down motion, Auto Key applied ease in, ease out to the ball’s forward motion. But this isn’t necessary, and in fact would give strange results when you repeat the bounce as you do in the next section.

1. In the Curve Editor Controller window, click the Y Position track to display the curve for that track.
2. Drag to select both the starting and the ending key in this track.
3. On the Track View - Curve Editor toolbar, click (Set Tangents To Linear).

   3ds Max Design removes the ease curves from this track, making the forward movement uniform.

Save your work:

- Save the scene as my_bouncing_basketball_adjusted.max.

Next

Repeat the Bounce