一种3D空间的柱状多边形检测实现

最近无意中拓展出这个东西，基于之前写的2D多边形检测:

http://www.cnblogs.com/hont/p/6105997.html

而判断两条线相交的方法替换成了我后来写的差乘判断:

http://www.cnblogs.com/hont/p/6106043.html

应用还是比较广泛的，特别是多边形选区和地形处理上

代码实现:

using UnityEngine;

public class Test : MonoBehaviour

{

    public Transform testComparePoint;

    public Transform[] pointsArray;

    public float height = ;

    public bool IsInRange(Vector3 comparePoint)

    {

        var localComparePoint = transform.worldToLocalMatrix.MultiplyPoint3x4(comparePoint);

        var flag = true;

        flag &= localComparePoint.y <= height;

        flag &= localComparePoint.y >= -height;

        flag &= IsConcaveContain2D(pointsArray, localComparePoint);

        if (flag)

            return true;

        return false;

    }

    public bool IsConcaveContain2D(Transform[] points, Vector3 compare)

    {

        const float VIRTUAL_RAYCAST_LEN = ;

        var comparePoint = (points[].localPosition + points[].localPosition) * 0.5f;

        var originPoint = compare;

        comparePoint += (comparePoint - originPoint).normalized * VIRTUAL_RAYCAST_LEN;

        int count = ;

        for (int i = ; i < points.Length; i++)

        {

            var a = points[i % points.Length];

            var b = points[(i + ) % points.Length];

            var r = IsLineSegmentIntersection(a.localPosition, b.localPosition, originPoint, comparePoint);

            if (r) count++;

        }

        return count %  == ;

    }

    public bool IsLineSegmentIntersection(Vector3 a, Vector3 b, Vector3 c, Vector3 d)

    {

        var crossA = Mathf.Sign(Vector3.Cross(d - c, a - c).y);

        var crossB = Mathf.Sign(Vector3.Cross(d - c, b - c).y);

        if (Mathf.Approximately(crossA, crossB)) return false;

        var crossC = Mathf.Sign(Vector3.Cross(b - a, c - a).y);

        var crossD = Mathf.Sign(Vector3.Cross(b - a, d - a).y);

        if (Mathf.Approximately(crossC, crossD)) return false;

        return true;

    }

    void OnDrawGizmos()

    {

        if (pointsArray == null) return;

        if (testComparePoint != null)

        {

            var comparePoint = testComparePoint.transform.position;

            if (IsInRange(comparePoint))

            {

                Gizmos.color = Color.red;

            }

        }

        var cacheMatrix = Gizmos.matrix;

        Gizmos.matrix = transform.localToWorldMatrix;

        for (int i = ; i < pointsArray.Length; i++)

        {

            var a = pointsArray[i];

            var b = pointsArray[(i + ) % pointsArray.Length];

            if (a == null) continue;

            if (b == null) continue;

            var minA = a.localPosition;

            var minB = b.localPosition;

            var maxA = a.localPosition;

            var maxB = b.localPosition;

            minA.y = -height;

            minB.y = -height;

            maxA.y = height;

            maxB.y = height;

            Gizmos.DrawLine(minA, minB);

            Gizmos.DrawLine(maxA, maxB);

            Gizmos.DrawLine(minA, maxA);

            Gizmos.DrawLine(minB, maxB);

        }

        Gizmos.color = Color.clear;

        Gizmos.matrix = cacheMatrix;

    }

}