Cubic.java

package cubic;
 
public class Cubic {
	public static final float cubic(float x, float... v) {
		if (x <= v[0]) {
			return v[1];
		}
		x = Math.min(Math.max(v[0], x), v[v.length - 2]);
		int i;
		for (i = 0; i < v.length && v[i + 6] < x; i += 6);
		float left = 0.0f;
		float right = 1.0f;
		float t = 0.5f;
		for (int n = 0; n < 15; n++) {
			float v1 = left*left*left*v[i+6] - (left*left*left - 3.0f*left*left + 3.0f*left - 1)*v[i] + 3.0f*(left*left*left - 2.0f*left*left + left)*v[i+2] - 3.0f*(left*left*left - left*left)*v[i+4];
			float v2 = t*t*t*v[i+6] - (t*t*t - 3.0f*t*t + 3.0f*t - 1)*v[i] + 3.0f*(t*t*t - 2.0f*t*t + t)*v[i+2] - 3.0f*(t*t*t - t*t)*v[i+4];
			right = v1 < x != v2 < x ? t : right;
			left = v1 < x != v2 < x ? left : t;
			t = (right - left) / 2.0f + left;
		}
		return t*t*t*v[i + 7] - (t*t*t - 3.0f*t*t + 3.0f*t - 1)*v[i + 1] + 3.0f*(t*t*t - 2.0f*t*t + t)*v[i + 3] - 3.0f*(t*t*t - t*t)*v[i + 5];
	}
}