Using Easing Functions in p5.js

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Easing functions are the unsung heroes of animations. They give life to dull, linear movements and add a touch of realism to our digital worlds. The p5.js library makes it easy to incorporate easing functions into your animations, elevating them to a higher level of sophistication. Let's dive right in and explore the magic of easing functions in p5.js!

What are easing functions?

Easing functions are mathematical formulas used to create non-linear interpolations between two values. In simpler terms, they help to smoothly vary an object's speed or position during an animation. Easing functions can be used to create natural-looking, organic movements that mimic real-world physics.

In p5.js, easing functions are built into the lerp() function, which stands for "linear interpolation." It allows us to blend between two values based on a specific input, called the interpolation factor.

A simple example

Imagine a ball that needs to move from point A to point B. Without easing, the ball would just move at a constant speed, which isn't very exciting. Let's see how we can use easing functions to make this animation more interesting:

let startX = 10; let startY = 40; let endX = 300; let endY = 200; let t = 0; function setup() { createCanvas(400, 400); } function draw() { background(220); let x = lerp(startX, endX, t); let y = lerp(startY, endY, t); // Update the interpolation factor (t) with a simple easing function t += (1 - t) * 0.05; // Draw the ball fill(255, 0, 0); ellipse(x, y, 20, 20); }

In this example, we use the lerp() function to interpolate the x and y coordinates of the ball. We also define an easing function (1 - t) * 0.05 to update the interpolation factor t. The result is a smooth animation where the ball starts fast and slows down as it approaches its destination.

Exploring other easing functions

There are many different easing functions that you can use to create interesting animations. Some popular ones include:

  • Quadratic: t * t
  • Cubic: t * t * t
  • Sinusoidal: sin(t * PI / 2)
  • Exponential: pow(2, 10 * (t - 1))

You can experiment with different easing functions by replacing the formula in the example above. Remember, the key is to find the right balance between realism and artistic expression.


Easing functions are a powerful tool for creating believable animations in p5.js. By understanding the concepts behind them and experimenting with different formulas, you can bring your sketches to life and wow your audience with smooth, natural-looking movements. So, go ahead and sprinkle some easing magic on your next p5.js project!


What are easing functions and why should I use them in my p5.js animations?

Easing functions are mathematical formulas used to create smooth and natural transitions in animations. They help control the rate at which an element moves from one position to another, often giving a more realistic and visually appealing result. Using easing functions in your p5.js animations can greatly enhance the overall look and feel of your projects.

How do I use an easing function in p5.js?

To use an easing function in p5.js, you can use the lerp() function, which stands for "linear interpolation." This function takes three arguments: the start value, the end value, and a value between 0 and 1 that represents the interpolation amount. Here's an example in JavaScript:

let startX = 0; let endX = 100; let interpolationAmount = 0.1; let currentX = lerp(startX, endX, interpolationAmount);

You can adjust the interpolation amount to control the rate of change between the start and end values, and experiment with different easing functions to achieve the desired result.

Can I create custom easing functions in p5.js?

Yes, you can create your own custom easing functions in p5.js. To do this, you'll need to define a function that takes a single parameter, typically called t (for time), and returns a value based on a mathematical formula. Here's an example of a custom easing function:

function myEasingFunction(t) { return t * t * (3 - 2 * t); }

Then, you can use this custom easing function in combination with lerp() to create smooth animations.

Are there any built-in easing functions in p5.js?

While p5.js doesn't have built-in easing functions like some other animation libraries, you can easily create custom easing functions or find examples online to use in your projects. Additionally, there are many resources and websites that provide a wide range of easing functions that you can use in your p5.js animations.

Can I use easing functions with colors, rotation, or scale in p5.js?

Absolutely! Easing functions can be used with any property that you want to animate smoothly in p5.js. For example, you can use lerpColor() to interpolate between colors, and apply easing functions to the rotation and scale of objects using the same lerp() function. Simply replace the start and end values with the properties you want to animate and adjust the interpolation amount accordingly.

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