unity3d：两条线段相交并求交点坐标

 public static float Cross(Vector2 a, Vector2 b)
    {
        return a.x * b.y - b.x * a.y;
    }

    public static bool SegmentsInterPoint(Vector2 a, Vector2 b, Vector2 c, Vector2 d, ref Vector2 IntrPos)
    {

        //v1×v2=x1y2-y1x2 
        //以线段ab为准，是否c，d在同一侧
        Vector2 ab = b - a;
        Vector2 ac = c - a;
        float abXac = Cross(ab,ac);

        Vector2 ad = d - a;
        float abXad = Cross(ab, ad);

        if (abXac * abXad >= 0)
        {
            return false;
        }

        //以线段cd为准，是否ab在同一侧
        Vector2 cd = d - c;
        Vector2 ca = a - c;
        Vector2 cb = b - c;

        float cdXca = Cross(cd, ca);
        float cdXcb = Cross(cd, cb);
        if (cdXca * cdXcb >= 0)
        {
            return false;
        }
        //计算交点坐标  
        float t = Cross(a -c, d -c) / Cross (d-c,b-a);
        float dx = t * (b.x - a.x);
        float dy = t * (b.y - a.y);

        IntrPos = new Vector2() { x = a.x + dx, y = a.y + dy };
        return true;
    }