Bouncing Ball – Part 2


In the first post in this series, I used the built-in Bounce motion path with some other effects to create bouncing ball animations. In this post, I’ll draw motion paths for the bouncing ball in segments; this way I can control the speed (sort of) to get a little more realistic action and synchronize the motion of the ball with other effects.

You can draw the paths by eye or you can take a more “scientific” approach.  One way to approximate the path is to assume that the distances traveled are reduced by a fixed percentage at each bounce. This set of drawing guides was created by reducing the vertical distance by a third and the horizontal distance by 25% at each bounce:

bounce2 1

I may document more detail on the creation of this layout later (no mathematics were used!).

The intersections of the drawing guides are used to help draw the motion paths. If you want to eyeball the paths, you can use the paths I develop here as prototypes.

The first motion path represents the “drop” of the ball to the first bounce. Select the ball and then, in the Custom Animation pane, select Add Effect and Motion Paths/Draw Custom Path/Curve. Click near the center of the ball and draw a path directly to the first bounce point:

bounce2 2

To shape the path. manipulate the “handles” on the motion path: right click on the path and select Edit Points. Right click on the first point and change the point to a Straight Point (!!) so that a handle appears. Move the handle horizontally to shape the top of the curve. Use the handle on the bottom point to shape the curve so that the “drop” is nearly vertical:

bounce2 3

My post on editing motion paths might be helpful.

To add the first full cycle, click on the ball and add another Curve motion path. Click at the end of the first path, at the top of this segment, and at the end/bottom of the segment:

bounce2 4

Once you have double clicked to complete the path, PowerPoint will move it back to the ball object. This is because PowerPoint designers have decided that you don’t really want the path where you put it:

bounce2 5

Just select the path and drag it back to the end of the first path. I use the path as it is (the default for the 3-point Curve); if you want to modify the shape, use the handles as before.

Continue to add segments to create the entire animation; unclick the smooth start/end option for each path. The last segment has a flat part added to allow the ball to come to a gradual stop:

bounce2 6

The duration for each segment is 0.5 sec, except for the first “half segment” which is 0.3 sec. Here’s what it looks like:

You will notice that this is a little different in timing than the built-in Bounce animation I used in the first post. The bounces near the end of the built-in effect appear too fast; this is closer to reality.

Here’s a version with modified durations:

Here’s the timing for this version:

bounce2 7

Note that this is an expanded view of the time scale. Smooth End is selected for the last segment.

One of the issues that remains is the behavior of the ball during the hops. A real bouncing  ball will slow near the top of the bounce; in fact the vertical component of velocity will pass through zero. This problem is most obvious (I think) in the first bounce so I broke the first bounce into 3 segments and slowed the segment corresponding to the top of the bounce:

bounce2 8

Here’s what this looks like:

You could break all the bounces into three parts but this is as far as I am prepared to go.

As a matter of fact, you may choose to ignore all this arcanery and use the built-in effect. However, there is an advantage to using the multiple segments (as I will show in the next post) even if you don’t want to fiddle with the timing.

If you want a free copy of the PowerPoint file for this post or if you have a comment or question, please use this form:

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