Thread by @mattdesl

Linear interpolation (sometimes called 'lerp' or 'mix') is a really handy function for creative coding, gamedev and generative art.

The function interpolates within the range [start..end] based on a 't' parameter, where 't' is typically within a [0..1] range.

A thread...

For example, divide 'loop time' by 'loop duration' and you get a 't' value between 0..1.

Now you can map this 't' value to a new range, such as `lerp(20, 50, t)` to gradually increase a circle's radius, or `lerp(20, 10, t)` to gradually decrease its line thickness.

Another example: you can use linear interpolation to smoothly animate from one coordinate to another. Define a start point (x1, y1) and end point (x2, y2), then interpolate the 'x' and 'y' dimensions separately to find the computed point in between.

Or use linear interpolation to spring toward a moving target. Each frame, interpolate from the current value to the target value with a small 't' parameter, such as 0.05.

It's like saying: walk 5% toward the target each frame.

A more advanced example, but built on the same concept, is interpolating from one color (red) to another (blue).

To do this, we interpolate the (R, G, B) or (H, S, L) channels of the color individually, just like we would with a 2D or 3D coordinate.

Source code for each of these examples:
gist.github.com/mattdesl/3675c…

Another quick example is to choose a random point along a line segment.

There are lots of ways to use linear interpolation, and lots more types of interpolation (cubic, bilinear, etc). These concepts also lead nicely into areas like: curves, splines and parametric equations.

The original thread is no longer showing on Twitter for whatever reason, so I’ve put all the code and examples into a blog post:

mattdesl.svbtle.com/linear-interpo…