Animate a Bouncing Ball in Pencil2D

Build a looping bouncing ball GIF using core animation principles.

Introduction

30 Second Summary

Every cartoon, video game, and motion graphic you have ever watched is built from the same trick: still images shown fast enough that your brain sees movement. Understanding how to control that trick is what separates a flat slideshow from animation that feels alive.

In this project, you will learn the four foundational principles of animation and apply them hands-on by creating a bouncing ball in Pencil2D. You will export the finished result as a looping GIF you can share anywhere.

What You'll Build

A hand-drawn bouncing ball animation that demonstrates professional animation principles including timing, spacing, squash and stretch, and arcs.

By the end of this project, you'll have:

A solid understanding of how animation creates the illusion of movement through frames, frame rates, and persistence of vision.
Internalized the four core animation principles (timing, spacing, squash and stretch, arcs) and the pose-to-pose workflow used by professional animators.
A finished 12-frame bouncing ball animation exported as a looping GIF that demonstrates all the principles you learned.
Secret Mission: Give your ball a personality by making it travel across the screen with diminishing bounces that show energy loss.

Are there any prerequisites?

You need a Mac with Pencil2D v0.7.2 installed. Pencil2D is free and open-source. No drawing tablet is required. A trackpad works perfectly for the simple shapes in this project.

Before We Start

Before We Start...

Understand How Animation Works

Before you draw a single frame, you need to understand what makes animation work. The principles you learn here will guide every decision you make when you start animating in Pencil2D.

This step is pure theory with no software required. You will learn how still images trick your brain into seeing motion, how frame rates work, and why the bouncing ball is every animator's first exercise.

In this step, get ready to:

Understand how still frames create the illusion of movement through persistence of vision.
Learn how frame rates work and what it means to animate on 1s, 2s, and 3s.
Discover why the bouncing ball is the universal first exercise for animators.

The illusion of movement

Animation is a series of still images displayed in rapid succession. Each image shows a slightly different position or shape.

When played back fast enough, your brain fills in the gaps and perceives continuous movement. This phenomenon is called persistence of vision.

What is persistence of vision?

Your brain retains an image for a fraction of a second after it disappears. When the next image appears before that memory fades, your brain blends them together into smooth motion.

This is the same principle behind flipbooks, film projectors, and every animated movie ever made. Each "frame" is just a single still image in that sequence.

Frame rates and shooting on 1s, 2s, and 3s

Frame rate is how many frames display per second (fps). It determines the overall smoothness of your animation.

Common frame rates are 12 fps for web animation, 24 fps for film, and 30 fps for video. Within any frame rate, animators also choose how often to draw a new image.

What does shooting on 1s, 2s, or 3s mean?

Shooting on 1s means a new drawing every single frame. This creates extremely fluid motion and is typically used for fast action sequences.

Shooting on 2s means a new drawing every two frames. This is the industry standard for hand-drawn animation because it balances smoothness with workload.

Shooting on 3s means a new drawing every three frames, producing slower and more deliberate movement. Most traditional animation is done on 2s.

How does this apply to your Pencil2D project?

Pencil2D defaults to 12 fps. At this frame rate, shooting on 1s means you draw 12 unique images for every second of animation.

For comparison, at 24 fps on 2s you would also draw 12 unique images per second. Your bouncing ball project will use 12 fps on 1s, giving you the simplest mental model: one drawing equals one frame.

Why the bouncing ball is the animator's first exercise

The bouncing ball is animation's equivalent of "Hello World." It teaches four core principles simultaneously using the simplest possible shape: a circle.

Timing controls how fast or slow the ball moves.
Spacing controls how far the ball travels between each frame.
Squash and stretch gives the ball weight and flexibility.
Arcs create natural curved motion paths.

Every animation school in the world starts with this exercise. If you can make a simple circle feel alive and believable, you understand the mechanics that make any character move convincingly.

Now that you understand the fundamentals of how animation works, you are ready to learn the four core principles that will make your bouncing ball feel alive and weighted.

Learn the Core Animation Principles

You now understand how animation creates the illusion of movement through frames, and how frame rates determine the smoothness of that motion.

But knowing how many frames to draw is only half the story. The real question is: where do you place the ball in each frame, and what shape should it be?

In this step, you will learn four animation principles that answer those questions. These principles are what separate a lifeless sequence of circles from a ball that feels like it has real weight and momentum.

In this step, get ready to:

Understand timing and spacing (how to create acceleration and deceleration).
Learn squash and stretch (how to show weight and impact).
Learn arcs and the pose-to-pose workflow (how professionals plan their animations).

Timing and spacing

These two concepts work together to create the feel of motion. Timing is how many frames an action takes. Spacing is how far the object moves between each frame.

For a bouncing ball, gravity does all the work. As gravity pulls the ball down, each frame shows a bigger position change. As the ball rises back up and fights gravity, each frame shows a smaller position change.

What do tight and wide spacing look like?

Imagine dropping a ball from chest height and watching it fall one photo at a time.

Tight spacing means the ball barely moves between frames. This happens at the top of each bounce where the ball slows to a stop before reversing direction.
Wide spacing means the ball covers a large distance between frames. This happens during the fall as the ball accelerates toward the ground.

The ball moves fastest at ground impact and slowest at the top of the arc.

A practical spacing rule

Use tight spacing at the top of each bounce (the ball slows down). Use wide spacing during the fall (the ball speeds up). Place more frames near the squash point to hold the impact and let the viewer feel the hit.

Squash and stretch

Squash and stretch is the most important of the 12 animation principles. It gives objects a sense of weight, flexibility, and life.

When the ball hits the ground, it squashes (flattens wider and gets shorter) to show the force of impact. When it rebounds upward with speed, it stretches (elongates taller and gets narrower) to show velocity.

Why must volume stay constant?

The critical rule of squash and stretch is that volume never changes. When you squash the ball shorter, it must get wider by the same amount. When you stretch it taller, it gets thinner.

This preserves the illusion of mass. If the ball got smaller during squash, it would look like it was deflating. If it got bigger during stretch, it would look like it was inflating. Consistent volume tells the viewer this is a solid object being deformed by force, not changing in size.

Squash and stretch guidelines

A good starting ratio is squashing to about 50-60% of the ball's normal height at impact.
The half-way position between key poses should always remain a perfect sphere.
Only squash at ground contact, and only stretch near impact during the fastest parts of the motion.

Arcs and the pose-to-pose workflow

Almost everything in nature moves in curved paths, not straight lines. Your bouncing ball follows a parabolic arc. Even a ball bouncing straight up and down curves slightly.

Always check that your drawings fall along a smooth arc. If any single drawing sits off the curve, the motion will stutter at that frame.

What is the pose-to-pose workflow?

Professional animators do not draw frame 1, then frame 2, then frame 3 in sequence. Instead they draw in three deliberate stages that give maximum control over the motion.

Key poses first. These are the main positions where the action changes direction. For your ball, that means the top of the bounce and the ground impact.
Breakdowns next. These are the drawings between keys that define the path and speed. For your ball, the stretch drawings near impact are breakdowns.
In-betweens last. These are the remaining frames that smooth everything out. They fill the gaps once you are happy with the keys and breakdowns.

Why not just draw in order?

Drawing in sequence (frame 1, 2, 3, 4...) means you cannot see the big picture until you are already committed to dozens of drawings. If the motion feels wrong at frame 20, you have to redo everything.

Pose-to-pose lets you test the overall motion with just 2-3 key drawings. You can adjust the entire arc, timing, and feel before investing time in the in-between frames.

You now have all four principles locked in: timing, spacing, squash and stretch, and arcs. Next up, you will open Pencil2D and get oriented in the workspace before putting these principles into action.

Get Oriented in Pencil2D

You now have four animation principles ready to apply: timing, spacing, squash and stretch, and arcs.

In this step, you'll open Pencil2D and get familiar with where everything lives. Knowing the workspace before you start animating means you won't lose momentum hunting for buttons later.

In this step, get ready to:

Identify the canvas, timeline, toolbox, and layers panel.
Try the Pencil, Eraser, Fill, and Select tools.
Enable onion skinning and play back a two-frame animation.

Explore the workspace

Pencil2D has four main areas you'll use throughout this project. Before you start drawing, take a moment to identify each one.

Press Cmd+Space to open Spotlight search.
Type Pencil2D and press Enter to open it.
Look at the center of the screen. This is the Canvas where you draw.
Look at the bottom of the screen. This is the Timeline, which shows your frames as numbered cells.
Look at the left side. This is the Toolbox containing your drawing tools.
Look at the area around the timeline. This is the Layers panel, showing your layer stack.
In the Layers panel, notice the default Bitmap Layer. This is where you will draw.
Click on a few different numbered frames in the timeline to navigate between them.

What are the four areas?

The Canvas is your drawing surface. The Timeline is where you control which frame you're on. The Toolbox holds all your brushes and selection tools. The Layers panel lets you stack drawings on separate layers, just like tracing paper.

Each frame in the timeline is a blank canvas until you draw on it.

Try the drawing tools

You'll use four tools throughout this project. Get comfortable with each one before you start animating.

Select the Pencil tool from the toolbox (shortcut: N).
Draw a rough circle anywhere on the canvas.
Adjust the brush size in the Tool Options panel that appears when the Pencil tool is selected.
Try the Eraser tool (shortcut: E) to remove part of your drawing.
Try the Paint Bucket/Fill tool (shortcut: K) to fill a closed shape with a flat color.
Try the Select tool (shortcut: V) to select and move things around on the canvas.
Use two-finger pinch on your trackpad to zoom in and out of the canvas.
Use two-finger drag on your trackpad to pan around the canvas.

Rough is fine

Do not worry about drawing perfect circles. Animation is rough and sketchy by nature. Your bouncing ball will look great even with imperfect shapes.

Understand the timeline and onion skinning

The timeline is where your animation lives frame by frame. Combined with onion skinning, it lets you see where your drawings came from and where they're going.

Click on frame 1 in the timeline and draw a simple shape (a circle or square).
Press the period key (.) to advance one frame forward to frame 2.
Draw something slightly different on frame 2 (move your shape to a new position or change its size).
Press Enter to play your two-frame animation.
Press Enter again to stop playback.

You should see your two drawings alternating rapidly. That's animation at its simplest.

Enable onion skinning by going to View in the menu bar, then clicking Onion Skin to toggle it on.
Click between frame 1 and frame 2 in the timeline.

You should now see a faded ghost of the adjacent frame overlaid on your canvas. This ghost shows where your drawing was (or will be) on nearby frames.

What is onion skinning?

Onion skinning shows faded versions of the previous and next frames while you draw on the current frame. It's named after the translucent layers of an onion.

This is essential for smooth animation because you can see exactly where the ball was and where it needs to go. Leave onion skinning toggled on for the rest of this project.

Don't see the ghost overlay?

Make sure you have drawings on at least two frames. Onion skinning only shows something when adjacent frames contain content.

If you toggled onion skinning on but still see nothing, check that View > Onion Skin has a checkmark next to it.

Help me turn on onion skinning in Pencil2D.

Your workspace is set up and you know where everything lives. Next up, you'll plan your animation timing and draw the key poses that form the skeleton of your bouncing ball.

Plan and Draw Your Key Poses

You now know your way around Pencil2D and understand the theory behind animation. Time to put it all together.

In this step, you will apply the pose-to-pose workflow to create the skeleton of your bouncing ball animation. You will draw the key poses first, then add the breakdown drawings that give the bounce its snap.

In this step, get ready to:

Set up a 12-frame timeline for a one-second loop.
Draw the two key poses (top of bounce and ground impact).
Draw the breakdown drawings (stretch before and after impact).

Set up your project and plan the timing

A clean project keeps your animation organized from the start. You need 12 frames for a one-second loop at 12 fps on 1s, plus a separate layer for the ground line so it does not interfere with your ball drawings.

In Pencil2D, click File in the menu bar.
Click New to create a fresh project.
Look at the timeline at the bottom of the screen. You should see a single frame on your default Bitmap Layer.
Add frames by pressing F7 repeatedly until you have frames 1 through 12 in the timeline.
You can also click the + button above the timeline to add blank keyframes.

Why 12 frames?

Pencil2D defaults to 12 fps. With 12 frames shot on 1s (one drawing per frame), you get exactly one second of animation.

This one-second cycle will loop seamlessly, making it the perfect length for a bouncing ball exercise.

Now create a separate layer for your ground line.

In the Layers panel (part of the timeline area), click the + button to add a new Bitmap Layer.
Double-click the new layer's name and rename it to something like Ground.
Select the Ground layer by clicking on it in the Layers panel.
Select the Pencil tool from the toolbox (shortcut: N).
Draw a horizontal line near the bottom of the canvas. This is your ground line where the ball will land.
Click on the original Bitmap Layer (your animation layer) to select it. All ball drawings will go on this layer.

Why use separate layers?

The ground line stays constant across all 12 frames. By putting it on its own layer, you draw it once and it appears behind every frame of animation automatically.

If you drew it on the same layer as your ball, you would have to redraw it on every single frame.

Don't see 12 frames in the timeline?

Make sure you are clicking F7 (not F6) to add blank keyframes. Count the numbered cells in the timeline to confirm you have 12.

If you accidentally added too many, right-click on the extra frame and select Remove Frame.

help me set up my Pencil2D timeline with 12 frames

Draw Key Pose 1 (frame 1) and Key Pose 2 (frame 7)

Key poses are the main positions where the action changes direction. For a bouncing ball, those are the top of the bounce (frame 1) and the ground impact (frame 7).

Click on frame 1 in the timeline.
With the Pencil tool selected, draw a circle (your ball) positioned high on the canvas, well above the ground line.
Keep it roughly the size of a coin on screen. This is the top of the bounce where the ball is momentarily still.

Circles do not need to be perfect

Animation is rough and sketchy by nature. A hand-drawn circle that is slightly uneven looks more alive than a perfectly geometric one. Focus on consistent size, not perfection.

Now draw the ground impact pose.

Click on frame 7 in the timeline.
Draw the ball at the ground line, squashed to about 50-60% of its normal height.
Make the squashed ball wider than the circle in frame 1 to compensate for the lost height. This preserves volume.
Position the bottom of the squashed ball so it sits directly on the ground line.

What does volume conservation look like?

Imagine your ball is a water balloon. When it squashes flat, all that water has to go somewhere, so it spreads wider.

The total area of your squashed drawing should feel roughly the same as the round ball in frame 1. If the squash looks like it lost mass, make it wider.

Draw the breakdown drawings (frames 6 and 8)

Breakdowns define the path and speed between key poses. For a bouncing ball, the breakdowns are the stretch drawings that show maximum velocity just before and just after impact.

Click on frame 6 in the timeline.
With onion skinning on, you should see faded ghosts of your drawings on frames 1 and 7.
Draw the ball elongated (taller and narrower than normal) positioned just above the ground line. This is the stretch that shows the ball falling fast toward the ground.

Now draw the post-impact stretch.

Click on frame 8 in the timeline.
Draw the ball stretched (taller and narrower) just above the ground line, as if it is shooting back upward after the bounce.

Why no round ball between stretch and squash?

The ball goes from stretch (frame 6) directly to squash (frame 7) and back to stretch (frame 8) with no transition drawings between them. This gives snap to the ball's bounce.

If you added a round drawing between the stretch and squash, the impact would feel mushy instead of punchy.

Test your work so far.

Press Enter (or click the Play button) to play back your animation.
You should see a rough suggestion of a bounce with squash and stretch at impact, even though frames 2-5 and 9-12 are still empty.

Animation looks like a slideshow of random shapes?

Make sure all your ball drawings are on the same layer (your animation layer, not the ground layer). Click the layer name in the Layers panel to confirm which layer is selected before drawing.

Also check that onion skinning is still enabled. If you cannot see the ghost of adjacent frames while drawing, toggle it back on from the View menu.

help me troubleshoot my Pencil2D bouncing ball key poses

Your animation's skeleton is in place. Next up, you will fill in the remaining frames to create smooth, weighted motion that actually feels like a real bouncing ball.

Add In-Betweens, Color, and Export

You have the skeleton of your bounce in place. The key poses (frames 1 and 7) define the extremes, and the breakdown drawings (frames 6 and 8) give the impact its snap.

Now you will fill in the remaining frames to complete the motion, making the ball accelerate downward and decelerate upward. Then you will add color and export a looping GIF you can share anywhere.

In this step, get ready to:

Draw the in-between frames (2-5 and 9-12) with correct spacing for acceleration and deceleration.
Test and refine your loop, then fill each frame with color.
Export your finished animation as a looping animated GIF.

Draw the in-between frames (2-5 and 9-12)

The empty frames between your key poses are where the principles of timing and spacing come alive. Each frame's position relative to the last one determines how fast the ball appears to move.

Draw frames 2-5 (the fall)

Click on frame 2 in the timeline. Make sure you are on your animation layer (not the ground layer).
With onion skinning on, you will see the ghost of frame 1 (the ball at the top). Draw a round sphere positioned just slightly below frame 1.
Click on frame 3. Draw the ball a little further down than the gap between frames 1 and 2. The spacing is growing because gravity is accelerating the ball.
Click on frame 4. Draw the ball even further down. The gap between frame 3 and frame 4 should be noticeably larger than the gap between frames 2 and 3.
Click on frame 5. Draw the ball positioned close to frame 6 (the stretch drawing). The gap between frames 4 and 5 is the widest yet.
Keep the ball as a perfect round sphere in frames 2-5. No squash or stretch yet.

What does the spacing accomplish?

Tight spacing near the top (frames 1-2-3) makes the ball look like it is slowing to a stop before reversing. Wide spacing near the bottom (frames 4-5) makes it feel like gravity is pulling it faster and faster.

This is the core illusion of weight. Without varied spacing, the ball would look like it is sliding on rails instead of being pulled by gravity.

Draw frames 9-12 (the rise)

Click on frame 9. With onion skinning showing frame 8 (the stretch after impact), draw the ball as a slightly stretched shape positioned well above the ground. The gap from frame 8 to frame 9 should be wide because the ball is still moving fast.
Click on frame 10. Draw the ball higher, returning to a round sphere shape. The gap is slightly smaller than between frames 8 and 9.
Click on frame 11. Draw a round sphere positioned higher still, with the gap continuing to shrink as the ball decelerates.
Click on frame 12. Draw the ball nearly at the same height as frame 1. The gap between frames 11 and 12 is the smallest, showing the ball is almost stopping before the loop restarts.

Why does the ball transition from stretched to round?

The ball is only stretched when it is moving at high speed near the ground (frames 6, 8, and partially frame 9). As it rises and decelerates, it returns to its natural round shape by frame 10 or 11.

The half-way position between key poses should always remain a sphere. Only the fastest moments near impact get the stretch treatment.

Press Enter to play back your animation and check that frames flow smoothly.

Ball looks like it's floating instead of bouncing?

If the ball moves at a constant speed, your spacing is too even. Go back and push frames 4-5 further apart (wider gaps during the fall) and push frames 11-12 closer together (tighter gaps as it rises).

If the ball seems to teleport between positions, you may have drawn on the wrong frame. Click each frame number in the timeline and confirm a drawing exists on each one.

Help me fix the spacing in my bouncing ball animation so it looks like it has weight.

Test, refine, and add color

With all 12 frames drawn, your animation loop is complete in pencil form. Before exporting, you will refine the motion and add color to make it polished.

Press Enter to play the full loop. Watch for the following:
Does the ball feel like it has weight? It should accelerate going down and decelerate going up.
Does the squash at frame 7 feel impactful? If it feels abrupt, confirm that frames 6 and 8 (the stretch drawings) are visible and positioned just above the ground.
Does the loop restart smoothly? Frame 12 should be at nearly the same height as frame 1.

Flip between frames manually

Press the period key (.) to advance one frame and the comma key (,) to go back one frame. This lets you scrub through your animation slowly and spot jumps or inconsistencies frame by frame.

If the ball feels floaty, increase the spacing gaps during the fall (redraw frames 4-5 lower).
If the squash feels weak, make frame 7 shorter and wider.
Once you are happy with the motion, select frame 1 by clicking it in the timeline.
Select the Paint Bucket/Fill tool from the toolbox (shortcut: K).
Click inside the ball to fill it with color. Choose any color you like from the color palette.
Advance to frame 2 and fill the ball again. Repeat for every frame (1-12) until all balls are filled with your chosen color.

Why fill each frame individually?

Each frame in traditional animation is a separate drawing. The fill tool only affects the current frame's drawing, not all frames at once. This is why hand-drawn animation is labor-intensive.

If the fill color leaks outside the ball, your outline has a gap. Use the Pencil tool (N) to close any openings in the outline, then try the fill again.

Press Enter to play the colored animation. You should see a solid-colored ball bouncing smoothly with visible acceleration, deceleration, squash, and stretch.

Fill color leaking everywhere?

The Paint Bucket floods any connected area of the same color. If your ball outline has even a tiny gap, the fill will escape and cover the entire canvas. Undo with Cmd+Z, find the gap in your outline, close it with the Pencil tool, then try filling again.

Help me fix the fill tool leaking outside my ball outline in Pencil2D.

Export as an animated GIF

Your animation is complete. Time to turn it into a file you can share with anyone.

First, save your project by going to File > Save As.
Name the file bouncing-ball and choose a save location you can find easily (like your Desktop). Pencil2D saves it as a .pclx file.
Now go to File > Export > Animated GIF.
In the export dialog, make sure the Loop checkbox is enabled so the GIF plays continuously.
Choose a save location and filename (like bouncing-ball.gif), then click OK.
Open the exported .gif file in Safari or Preview to verify it loops smoothly.

What is a .pclx file vs a .gif file?

The .pclx file is your editable project. It contains all your layers, frames, and settings so you can reopen and modify your animation later.

The .gif file is a flattened export. It merges all layers into a single looping image file that anyone can view, but it cannot be edited. Always keep your .pclx file as a backup.

Open your exported GIF. You should see a ball bouncing up and down in a smooth continuous loop with visible acceleration on the fall, deceleration on the rise, squash at ground impact, and stretch near the ground.

GIF not playing or showing an error?

If you see an error message during export, check that the save location exists and that you have write permissions to that folder. Try exporting to your Desktop instead.

If the GIF opens but does not animate, make sure you are viewing it in Safari or a web browser. The macOS Preview app sometimes displays only the first frame of an animated GIF.

Help me troubleshoot my Pencil2D GIF export that isn't working.

Secret mission

Give Your Ball a Personality

Your bouncing ball loops perfectly, but real bounces don't last forever. In this secret mission, you'll make your ball travel across the screen with diminishing bounces that lose energy over time. The result is a ball that feels like it has real weight and physical believability.

Clean Up Your Resources

This project runs entirely locally on your Mac, so there are no ongoing costs or cloud resources to worry about.

Decide whether to keep your files for future practice, or delete them if you are done.

Resources you used:

Pencil2D project file (bouncing-ball.pclx).
Exported GIF files (bouncing-ball.gif and bouncing-ball-traveling.gif).
Pencil2D application (installed in your Applications folder).

Keep everything running

No action needed. Choose this if you want to keep practicing animation or plan to revisit your bouncing ball project.

Your .pclx project file stays where you saved it, ready to reopen anytime.
Your exported GIFs are standard image files that take up minimal disk space.
Pencil2D remains installed in your Applications folder for future animation projects.

Pause - I'll come back to this later

Since everything is local and nothing is running in the background, there is nothing to pause. Your files sit on disk until you need them again.

Your project file and GIFs are safe on your Mac. No processes to stop.
When you are ready to come back, open Pencil2D and use File > Recent to find your project.

Delete - I don't want to use this again

Remove all project files and optionally uninstall Pencil2D.

Find your bouncing-ball.pclx file wherever you saved it (check your Desktop or Documents folder). Drag it to the Trash.
Find your exported GIF files (bouncing-ball.gif and bouncing-ball-traveling.gif) and drag them to the Trash.
To uninstall Pencil2D, open your Applications folder in Finder, find Pencil2D, and drag it to the Trash.
Empty the Trash to free up the disk space.

That's a Wrap!

Nice work! You just brought a simple circle to life using the same principles that power every animated film, game, and motion graphic.

You've learned how to:

Internalized four core animation principles (timing, spacing, squash and stretch, and arcs) and applied them to create believable motion from scratch.
Used the pose-to-pose workflow (keys, breakdowns, in-betweens) to plan and execute a 12-frame bouncing ball loop in Pencil2D.
Exported a finished animated GIF that loops seamlessly and demonstrates all four animation principles working together.
Secret Mission: Created a traveling bounce with diminishing energy, demonstrating how animators give objects weight and personality.

Ready to quiz yourself?