Unity3D数学基础（Vector3）

【向量（Vector3），解释】
https://blog.csdn.net/bobo553443/article/details/79481881
我们这里主要研究transform.forward，transform.up,transform.right发生了什么？
unity公布了源码，GitHub下载源码地址：https://codeload.github.com/Unity-Technologies/UnityCsReference/zip/master

image.png
接下来我们看下Transform源码中的定义和解释：

        // The red axis of the transform in world space.
        // 世界空间变换的红色轴
        public Vector3 right
        {
            get
            {
                return rotation * Vector3.right;
            }
            set
            {
                rotation = Quaternion.FromToRotation(Vector3.right, value);
            }
        }

        // The green axis of the transform in world space.
        // 世界空间变换的绿色轴
        public Vector3 up
        {
            get
            {
                return rotation * Vector3.up;
            }
            set
            {
                rotation = Quaternion.FromToRotation(Vector3.up, value);
            }
        }

        // The blue axis of the transform in world space.
        // 世界空间变换的蓝色轴
        public Vector3 forward
        {
            get
            {
                return rotation * Vector3.forward;
            }
            set
            {
                rotation = Quaternion.LookRotation(value);
            }
        }

我们看了源码，知道了，forward内部究竟发生了什么，
比如我们想要实现一个功能，当前玩家攻击目标玩家，发射一条线，一直跟随目标，怎么实现呢？先看效果：

GIF.gif

很简单的实现就是计算两点距离，等到距离设置line的目标长度z，实时看向目标使用LookAt函数，那么问题来了，LookAt函数和forward的区别在哪里?我们也可以设置forward来实现实时朝向一个目标吗？
看代码对比差别,forward上面有，下面是lookat的源码：

        // Rotates the transform so the forward vector points at /target/'s current position.
        public void LookAt(Transform target, [UnityEngine.Internal.DefaultValue("Vector3.up")] Vector3 worldUp)
        {
            if (target)
                LookAt(target.position, worldUp);
        }

        public void LookAt(Transform target)
        {
            if (target)
                LookAt(target.position, Vector3.up);
        }

        // Rotates the transform so the forward vector points at /worldPosition/.
        public void LookAt(Vector3 worldPosition, [UnityEngine.Internal.DefaultValue("Vector3.up")] Vector3 worldUp)
        {
            Internal_LookAt(worldPosition, worldUp);
        }

        public void LookAt(Vector3 worldPosition)
        {
            Internal_LookAt(worldPosition, Vector3.up);
        }

        [FreeFunction("Internal_LookAt", HasExplicitThis = true)]
        private extern void Internal_LookAt(Vector3 worldPosition, Vector3 worldUp);