Hermite Spline for Unity3D

SplineSection.cs

using UnityEngine;
using System.Collections;

public class SplineSection : MonoBehaviour {

	public Transform startPoint, startTangent, endPoint, endTangent;

	public SplineSection prev, next;

	public Vector3 GetPositionAt(float t) {
		if ((t < 0f) && (prev!=null) && prev.IsValid()) {
			return prev.GetPositionAt(t+1.0f);
		} else if ((t > 1f) && (next!=null) && next.IsValid()) {
			return next.GetPositionAt(t-1.0f);
		} else if (IsValid()) {
			float t2 = t*t;
			float t3 = t2*t;
			Vector3 p0 = startPoint.position, p1 = endPoint.position, m0 = startTangent.position - p0, m1 = endTangent.position - p1;
			return (p0 * ((2.0f*t3) - (3.0f*t2) + 1.0f))
				+ (m0 * (t3 + (-2.0f*t2) + t))
				+ (p1 * ((-2.0f*t3) + (3.0f*t2)))
				+ (m1 * (t3 - t2));
		} else {
			return transform.position;
		}
	}

	public bool IsValid() {
		return (startPoint != null) && (startTangent != null) && (endPoint != null) && (endTangent != null);
	}

	void OnDrawGizmos() {
		if(IsValid()) {
			Gizmos.color = Color.grey;
			Gizmos.DrawLine(startPoint.position, startTangent.position);
			Gizmos.DrawLine(endPoint.position, endTangent.position);
			for(int i = 0; i < 8; i++) {
				Gizmos.DrawLine(GetPositionAt(((float)i)/8f),
				                GetPositionAt(((float)(i+1))/8f));
			}
		}
	}

	void OnDrawGizmosSelected() {
		if(IsValid()) {
			Gizmos.color = Color.yellow;
			Gizmos.DrawLine(startPoint.position, startTangent.position);
			Gizmos.DrawLine(endPoint.position, endTangent.position);
			Gizmos.color = Color.white;
			for(int i = 0; i < 16; i++) {
				Gizmos.DrawLine(GetPositionAt(((float)i)/16f),GetPositionAt(((float)i+1)/16f));
			}
		}
	}
}