Getting Started

CubicBezier aims to replicate the CubicBezier timing function found in CSS used with the animation-timing-function property and the transition-timing-function property.

A Cubic Bezier curve is defined by four points p0, p1, p2, and p3. P0 and P3 are the start and the end of the curve and, in CSS these points are fixed as the coordinates are ratios. p0 is (0, 0) and represents the initial time and the initial state, p3 is (1, 1) and represents the final time and the final state.

Since time (x) is always between 0 and 1, it is useful to treat time and state as percentages. Where x is the percentage of time that has elapsed in your animation / transition, and y is the percentage of change between your object(s) start and end states.

Why?

Let's say you want to "tween" (animate / transition) an object's position. You might take the travel distance, and divide by the steps ("frames") of your tween. On every frame, you'd increment the object's position. This would be the equivelant of a linear Cubic Bezier; and it tends to look / feel very unnatural. To make the movement feel more natural, you'd use an "easing equation" (eg. CubicBezier.solve(x, :ease_out_quad)). To further make the animation feel more natural, you'd want to compute the object's position about 60 times per second (60 fps). This will smooth out the position changes to make it feel more fluid. The combination results in natural and fluid tweens!

Syntax

You can use atoms to represent common easing equatons, or pass a control point tuple. The examples below are equivelant:

iex> CubicBezier.solve(0.25, :ease_out_quad)
iex> CubicBezier.solve(0.25, {0.250,  0.460,  0.450,  0.940})

This will return a y state of ~0.45, given an x time of 0.25.

Ease-Out-Quad is fast at first, and slow towards the end.

Reference

• Easing function examples: https://easings.net/en