1 package aurelienribon.tweenengine.paths;
2 
3 import aurelienribon.tweenengine.TweenPath;
4 
5 /**
6  * @author Aurelien Ribon | http://www.aurelienribon.com/
7  */
8 public class CatmullRom implements TweenPath {
9 	@Override
compute(float t, float[] points, int pointsCnt)10 	public float compute(float t, float[] points, int pointsCnt) {
11 		int segment = (int) Math.floor((pointsCnt-1) * t);
12 		segment = Math.max(segment, 0);
13 		segment = Math.min(segment, pointsCnt-2);
14 
15 		t = t * (pointsCnt-1) - segment;
16 
17 		if (segment == 0) {
18 			return catmullRomSpline(points[0], points[0], points[1], points[2], t);
19 		}
20 
21 		if (segment == pointsCnt-2) {
22 			return catmullRomSpline(points[pointsCnt-3], points[pointsCnt-2], points[pointsCnt-1], points[pointsCnt-1], t);
23 		}
24 
25 		return catmullRomSpline(points[segment-1], points[segment], points[segment+1], points[segment+2], t);
26 	}
27 
catmullRomSpline(float a, float b, float c, float d, float t)28 	private float catmullRomSpline(float a, float b, float c, float d, float t) {
29 		float t1 = (c - a) * 0.5f;
30 		float t2 = (d - b) * 0.5f;
31 
32 		float h1 = +2 * t * t * t - 3 * t * t + 1;
33 		float h2 = -2 * t * t * t + 3 * t * t;
34 		float h3 = t * t * t - 2 * t * t + t;
35 		float h4 = t * t * t - t * t;
36 
37 		return b * h1 + c * h2 + t1 * h3 + t2 * h4;
38 	}
39 }
40