CrowdControl/Assets/Feel/MMTools/Tools/MMSprites/BezierLineRenderer/MMBezierLineRenderer.cs

using UnityEngine;
using System.Collections.Generic;

namespace MoreMountains.Tools
{
	/// <summary>
	/// Add this class to a line renderer and it'll add control points that let you turn your line into a bezier curve
	/// </summary>
	[ExecuteAlways]
	[RequireComponent(typeof(LineRenderer))]
	[AddComponentMenu("More Mountains/Tools/Sprites/MMBezierLineRenderer")]
	public class MMBezierLineRenderer : MonoBehaviour
	{
		/// a list of handles to control your line. Usually 4, but you can have more.
		public Transform[] AdjustmentHandles;
		/// the amount of segments of the line renderer (more segments, less visible straight lines)
		public int NumberOfSegments = 50;
		/// the sorting layer for this line renderer
		public string SortingLayerName = "Default";
		/// the amount of curves we're working with
		[MMReadOnly]
		public int NumberOfCurves = 0;

		protected int _sortingLayerID;
		protected LineRenderer _lineRenderer;
		protected Vector3 _point;
		protected Vector3 _p;
		protected bool _initialized = false;

		/// <summary>
		/// On Awake we initialize our line renderer 
		/// </summary>
		protected virtual void Awake()
		{
			Initialization();
		}

		/// <summary>
		/// Grabs the sorting layer, computes the amount of curves
		/// </summary>
		protected virtual void Initialization()
		{
			if (_initialized)
			{
				return;
			}

			_sortingLayerID = SortingLayer.NameToID(SortingLayerName);

			NumberOfCurves = (int)AdjustmentHandles.Length / 3;

			_lineRenderer = GetComponent<LineRenderer>();
			if (_lineRenderer != null)
			{
				_lineRenderer.sortingLayerID = _sortingLayerID;
			}
			_initialized = true;
		}

		/// <summary>
		/// On Update we draw our curve
		/// </summary>
		protected virtual void LateUpdate()
		{
			DrawCurve();
		}

		/// <summary>
		/// For each point, determines the bezier position and feeds it to the line renderer
		/// </summary>
		protected virtual void DrawCurve()
		{
			for (int i = 0; i < NumberOfCurves; i++)
			{
				for (int j = 1; j <= NumberOfSegments; j++)
				{
					float t = (j - 1) / (float)(NumberOfSegments - 1);
					int pointIndex = i * 3;
					_point = BezierPoint(t, AdjustmentHandles[pointIndex].position, AdjustmentHandles[pointIndex + 1].position, AdjustmentHandles[pointIndex + 2].position, AdjustmentHandles[pointIndex + 3].position);
					_lineRenderer.positionCount = (i * NumberOfSegments) + j;                    
					_lineRenderer.SetPosition((i * NumberOfSegments) + (j - 1), _point);
				}
			}
		}

		/// <summary>
		/// Computes the coordinates of a point on the bezier curve controlled by p0, p1, p2 and p3
		/// </summary>
		/// <param name="t"></param>
		/// <param name="p0"></param>
		/// <param name="p1"></param>
		/// <param name="p2"></param>
		/// <param name="p3"></param>
		/// <returns></returns>
		protected virtual Vector3 BezierPoint(float t, Vector3 p0, Vector3 p1, Vector3 p2, Vector3 p3)
		{
			float u = 1 - t;
			float tt = t * t;
			float uu = u * u;
			float uuu = uu * u;
			float ttt = tt * t;

			_p = uuu * p0;
			_p += 3 * uu * t * p1;
			_p += 3 * u * tt * p2;
			_p += ttt * p3;

			return _p;
		}
	}
}