Unity Vector

指向被减向量

// Gets a vector that points from the player's position to the target's.
var heading = target.position - player.position;

标准化向量

var distance = heading.magnitude;
var direction = heading / distance; // This is now the normalized direction.

比较距离，避免求平方根

if (heading.sqrMagnitude < maxRange * maxRange) {
    // Target is within range.
}

给三个点，计算三点所在平面的法向量

var a: Vector3;
var b: Vector3;
var c: Vector3;

var side1: Vector3 = b - a;
var side2: Vector3 = c - a;
var perp: Vector3 = Vector3.Cross(side1, side2);

标准化：

var perpLength = perp.magnitude;
perp /= perpLength;

 此三点构成的三角形的面积为perpLength/2。

某方向上的速度。例，前进方向的分速度。方向向量必须是单位向量（标准化向量）

 var fwdSpeed = Vector3.Dot(rigidbody.velocity, transform.forward);