catmullrom

Package catmullrom implements the centripetal Catmull-Rom spline and calculates points of a 2D spline curve given a series of control points.

Add it to a module as a dependency via:

go get github.com/fzipp/catmullrom

Example usage

Single spline

A single spline requires four control points (p0, p1, p2, p3). The resulting interpolated points of the spline curve are between the second and the third control point (p1 and p2).

package main

import (
	"fmt"

	"github.com/fzipp/catmullrom"
)

func main() {

	p := []catmullrom.Point{
		{X: 0, Y: 2.5},
		{X: 2, Y: 4},
		{X: 3, Y: 2},
		{X: 4, Y: 1.5},
	}

	curve := catmullrom.Spline(p[0], p[1], p[2], p[3], 100, 0.5)

	for _, point := range curve {
		fmt.Printf("%v\t%v\n", point.X, point.Y)
	}
}

Output:

2	4
2.014365414796725	3.9961683757388826
2.0285086520907125	3.991519010789197
2.0424338917428546	3.986066863428536
[...]
2.9631689321190793	2.0405052334680907
2.9752654723162837	2.026380248925892
2.9875411016562947	2.012873518343997
3	2

Spline chain

A spline chain goes through an arbitrary number of control points, including the first and the last control point.

package main

import (
	"fmt"

	"github.com/fzipp/catmullrom"
)

func main() {

	controlPoints := []catmullrom.Point{
		{X: 0, Y: 2.5},
		{X: 2, Y: 4},
		{X: 3, Y: 2},
		{X: 4, Y: 1.5},
		{X: 5, Y: 6},
		{X: 6, Y: 5},
		{X: 7, Y: 3},
		{X: 9, Y: 1},
		{X: 10, Y: 2.5},
		{X: 11, Y: 7},
		{X: 9, Y: 5},
		{X: 8, Y: 6},
		{X: 7, Y: 5.5},
	}

	curve := catmullrom.SplineChain(controlPoints, 100, 0.5)

	for _, point := range curve {
		fmt.Printf("%v\t%v\n", point.X, point.Y)
	}
}

Output:

0	2.5
0.020250950290489646	2.5153391496514774
0.040597763611450566	2.531045909751864
0.06103744424317995	2.5471087924746265
[...]
7.030349491470336	5.5157336988112
7.0202228847077075	5.5103624536889235
7.01010628000193	5.505116539771162
7	5.5

Visualized curve: