Vector3.ProjectOnPlane

# [Vector3](https://docs.unity3d.com/cn/2019.4/ScriptReference/Vector3.html).ProjectOnPlane

public static [Vector3](https://docs.unity3d.com/cn/2019.4/ScriptReference/Vector3.html) **ProjectOnPlane** ([Vector3](https://docs.unity3d.com/cn/2019.4/ScriptReference/Vector3.html) **vector**, [Vector3](https://docs.unity3d.com/cn/2019.4/ScriptReference/Vector3.html) **planeNormal**);

## 参数

| planeNormal | 从矢量到平面的方向。   |
| ------------- | ------------------------ |
| vector      | 平面上方的矢量的位置。 |

## 返回

**Vector3** 平面中的矢量的位置。

## 描述

将向量投影到由法线定义的平面上（法线与该平面正交）。

[Vector3](https://docs.unity3d.com/cn/2019.4/ScriptReference/Vector3.html) 将给定 [vector](https://docs.unity3d.com/cn/2019.4/ScriptReference/Vector3-vector.html) 的位置存储在 3D 空间中。另一个 [Vector3](https://docs.unity3d.com/cn/2019.4/ScriptReference/Vector3.html) 由 [planeNormal](https://docs.unity3d.com/cn/2019.4/ScriptReference/Vector3-planeNormal.html) 提供，用于定义通过原点从平面到 [vector](https://docs.unity3d.com/cn/2019.4/ScriptReference/Vector3-vector.html) 的方向。[Vector3.ProjectOnPlane](https://docs.unity3d.com/cn/2019.4/ScriptReference/Vector3.ProjectOnPlane.html) 使用两个 [Vector3](https://docs.unity3d.com/cn/2019.4/ScriptReference/Vector3.html) 值在 [planeNormal](https://docs.unity3d.com/cn/2019.4/ScriptReference/Vector3-planeNormal.html) 方向生成 [vector](https://docs.unity3d.com/cn/2019.4/ScriptReference/Vector3-vector.html) 的位置，并返回 [Vector3](https://docs.unity3d.com/cn/2019.4/ScriptReference/Vector3.html) 在平面上的位置。

![](/media/202206/1_1655866663.png)
*矢量从红色圆圈处开始，在黑色圆圈（代表平面法线）处结束。*

以下脚本示例使 `Update` 生成一个 `vector` 位置和一个 `planeNormal` 法线。[Vector3.ProjectOnPlane](https://docs.unity3d.com/cn/2019.4/ScriptReference/Vector3.ProjectOnPlane.html) 静态方法可接收参数并返回 [Vector3](https://docs.unity3d.com/cn/2019.4/ScriptReference/Vector3.html) 位置。

```
using System.Collections;
using System.Collections.Generic;
using UnityEngine;

// Vector3.ProjectOnPlane - example

// Generate a random plane in xy. Show the position of a random
// vector and a connection to the plane. The example shows nothing
// in the Game view but uses Update(). The script reference example
// uses Gizmos to show the positions and axes in the Scene.

public class Example : MonoBehaviour
{
    private Vector3 vector, planeNormal;
    private Vector3 response;
    private float radians;
    private float degrees;
    private float timer = 12345.0f;

// Generate the values for all the examples.
    // Change the example every two seconds.
    void Update()
    {
        if (timer > 2.0f)
        {
            // Generate a position inside xy space.
            vector = new Vector3(Random.Range(-1.0f, 1.0f), Random.Range(-1.0f, 1.0f), 0.0f);

// Compute a normal from the plane through the origin.
            degrees = Random.Range(-45.0f, 45.0f);
            radians = degrees * Mathf.Deg2Rad;
            planeNormal = new Vector3(Mathf.Cos(radians), Mathf.Sin(radians), 0.0f);

// Obtain the ProjectOnPlane result.
            response = Vector3.ProjectOnPlane(vector, planeNormal);

// Reset the timer.
            timer = 0.0f;
        }
        timer += Time.deltaTime;
    }

// Show a Scene view example.
    void OnDrawGizmosSelected()
    {
        // Left/right and up/down axes.
        Gizmos.color = Color.white;
        Gizmos.DrawLine(transform.position - new Vector3(2.25f, 0, 0), transform.position + new Vector3(2.25f, 0, 0));
        Gizmos.DrawLine(transform.position - new Vector3(0, 1.75f, 0), transform.position + new Vector3(0, 1.75f, 0));

// Display the plane.
        Gizmos.color = Color.green;
        Vector3 angle = new Vector3(-1.75f * Mathf.Sin(radians), 1.75f * Mathf.Cos(radians), 0.0f);
        Gizmos.DrawLine(transform.position - angle, transform.position + angle);

// Show a connection between vector and response.
        Gizmos.color = Color.yellow;
        Gizmos.DrawLine(vector, response);

// Now show the input position.
        Gizmos.color = Color.red;
        Gizmos.DrawSphere(vector, 0.05f);

// And finally the resulting position.
        Gizmos.color = Color.black;
        Gizmos.DrawSphere(response, 0.05f);
    }
}
```