unityzgy/Assets/Scripts/ZFramwork/Extend/BezierUtils.cs

using UnityEngine;


namespace XFramework.UIExtensions
{
    /**
     * Created by vivi on 16/5/11.
     */
    public class BezierUtils
    {
        public float P0x;
        public float P1x;
        public float P2x;
        public float P3x;



        public float P0y;
        public float P1y;
        public float P2y;
        public float P3y;


        public BezierUtils(float p0x, float p0y, float p1x, float p1y, float p2x, float p2y, float p3x, float p3y)
        {
            P0x = p0x;
            P0y = p0y;
            P1x = p1x;
            P1y = p1y;
            P2x = p2x;
            P2y = p2y;
            P3x = p3x;
            P3y = p3y;
        }


        public BezierUtils(Vector2 p0, Vector2 p1, Vector2 p2, Vector2 p3)
        {
            P0x = p0.x;
            P0y = p0.y;
            P1x = p1.x;
            P1y = p1.y;
            P2x = p2.x;
            P2y = p2.y;
            P3x = p3.x;
            P3y = p3.y;
        }


        public float beze_x(float t)
        {
            float it = 1 - t;
            return it * it * it * P0x + 3 * it * it * t * P1x + 3 * it * t * t * P2x + t * t * t * P3x;
        }
        public float beze_y(float t)
        {
            float it = 1 - t;
            return it * it * it * P0y + 3 * it * it * t * P1y + 3 * it * t * t * P2y + t * t * t * P3y;
        }

        //-------------------------------------------------------------------------------------

        public float beze_speed_x(float t)
        {
            float it = 1 - t;
            return -3 * P0x * it * it + 3 * P1x * it * it - 6 * P1x * it * t + 6 * P2x * it * t - 3 * P2x * t * t + 3 * P3x * t * t;

        }

        public float beze_speed_y(float t)
        {
            float it = 1 - t;
            return -3 * P0y * it * it + 3 * P1y * it * it - 6 * P1y * it * t + 6 * P2y * it * t - 3 * P2y * t * t + 3 * P3y * t * t;
        }

        private float beze_speed(float t)
        {
            float sx = beze_speed_x(t);
            float sy = beze_speed_y(t);
            return (float)Mathf.Sqrt(Mathf.Pow(sx, 2) + Mathf.Pow(sy, 2));
        }
        //-------------------------------------------------------------------------------------
        private float beze_length(float t)
        {
            float LATESTCOUNT = 10000;
            int steps = (int)Mathf.Ceil(LATESTCOUNT * t);
            if (steps == 0)
                return 0;
            if (steps % 2 != 0)
                steps++;
            float halfSteps = steps * .5f;
            float nSum = 0;
            float n1Sum = 0;
            float disStep = t / steps;

            for (int i = 0; i < halfSteps; i++)
            {
                n1Sum += beze_speed((2 * i + 1) * disStep);
                nSum += beze_speed(2 * i * disStep);
            }
            return (beze_speed(0) + beze_speed(1) + 2 * n1Sum + 4 * nSum) * disStep / 3;
        }
        //-------------------------------------------------------------------------------------
        private float beze_even(float t)
        {
            float len = t * beze_length(1);
            float uc = 0;
            do
            {
                float ulen = beze_length(t);
                float uspeed = beze_speed(t);
                uc = t - (ulen - len) / uspeed;
                if (Mathf.Abs(uc - t) < 0.0001)
                    break;

                t = uc;
            } while (true);

            return uc;
        }
        private float totallength = -1;
        public float getTotalLength()
        {
            if (totallength < 0)
                totallength = beze_length(1);
            return totallength;
        }

        public Vector2 getPosition(float t)
        {
            return new Vector2(beze_x(t), beze_y(t));
        }

    }

}