To make a ball bounce in Maya using keyframes, you typically animate the ball's vertical position (usually on the Y-axis) by setting keyframes at key moments like the peak of the bounce and the impact with the ground. The timing and height of these keyframes are then adjusted, often using the Graph Editor, to create a realistic bouncing motion that gradually comes to rest.
Understanding the Bouncing Ball Principle
Animating a bouncing ball is a fundamental exercise in 3D animation. It involves simulating the effects of gravity and energy loss over time. The key principles are:
- Gravity: The ball accelerates downwards between bounces.
- Impact: The ball deforms slightly on impact and loses energy, resulting in a lower bounce height each time.
- Timing: The bounces become closer together as the ball loses energy and the bounce height decreases.
Setting Up Initial Keyframes
Here are the basic steps to start keyframing a bounce:
- Select the Ball: Choose the 3D model of the ball you want to animate.
- Set Initial Position: Place the ball at its starting height (e.g., above the ground).
- Set First Keyframe: With the ball selected, press 's' on your keyboard or go to
Animate > Set Key. This records the ball's position at the current frame (Frame 1). - Set Ground Keyframe: Move the timeline to a later frame (e.g., Frame 10). Move the ball down so its bottom touches the ground. Press 's' again to set a keyframe at this position and time.
- Set Peak Keyframe: Move the timeline further (e.g., Frame 20). Move the ball back up to a lower height than the starting height. Press 's' to set another keyframe.
- Repeat: Continue this process, setting keyframes for each impact with the ground and each successive peak bounce, making the peak height lower each time.
Refining the Bounce with the Graph Editor
Setting keyframes is just the start. The Graph Editor is essential for giving the bounce a realistic feel.
- Access the Graph Editor: Go to
Windows > Animation Editors > Graph Editor. - Select Curves: In the Graph Editor, select the Y-Translate curve (since you are animating vertical movement).
| Keyframe Location | Typical Curve Shape Adjustment |
|---|---|
| Peak of Bounce | The curve should be relatively smooth and rounded at the top, showing the ball momentarily slowing down before accelerating downwards. |
| Ground Impact | The curve should have a sharp, V-like shape at the bottom. This indicates a sudden change in velocity upon impact. |
You will typically want to ensure the tangent type at the ground impact keyframes is set to "Linear" or "Spline" and adjusted to create the sharp change in direction, while tangents at the peaks are "Auto" or "Spline" for a smooth transition.
Adjusting Timing for Realism
As the reference mentions, you need to make the keyframes "faster and faster" to simulate the ball coming to rest. This means the time between bounces decreases as the ball loses energy.
- Shorten Intervals: In the Graph Editor or on the timeline, move the keyframes for successive bounces closer together. The distance between the ground impact keys and subsequent peak keys should get progressively smaller.
- Example: If the first bounce takes 10 frames to hit the ground and 10 frames to reach the peak (total 20 frames for one bounce cycle), the next cycle might take 8 frames down and 8 frames up (total 16 frames), then 6 down and 6 up, and so on.
The reference highlights this crucial point: "...make this ball look like it's slowly coming to rest. So we went to 14." This likely refers to adjusting the timing of keyframes around frame 14 to make the bounces happen faster as the energy dissipates, leading to the ball settling.
By carefully adjusting the timing of your keyframes and refining the curves in the Graph Editor, you can create a convincing bouncing ball animation where the bounces become shorter in height and faster in frequency until the ball stops.
