序

比如，目前导入了一个obj文件，想知道它的AABB包围盒是什么。

官方文档

Unity - Scripting API: Bounds (unity3d.com)

可以看到，包围盒有三个类别的：

Mesh.bounds

Unity - Scripting API: Mesh.bounds (unity3d.com)

不随gameobject的几何变换而变换，大概是直接用obj里的顶点坐标算出来的；也就是所谓的模型坐标系。

api怎么调用的？主要就是这几句：

试一试

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

public class BoundTest : MonoBehaviour
{
    // Start is called before the first frame update
    void Start()
    {
        Mesh mesh = GetComponent<MeshFilter>().mesh;
        Bounds bounds = mesh.bounds;
        print(bounds.center); // 把文档里的属性，都打印出来看看
        print(bounds.size);
        print(bounds.min);
        print(bounds.max);
        print(bounds.extents);
    }

    // Update is called once per frame
    void Update()
    {
        
    }
}

关于文档里面not change的演示：

代码：

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

public class BoundTest : MonoBehaviour
{
    private Mesh mesh;
    private Bounds bounds;

    // Start is called before the first frame update
    void Start()
    {

        mesh = GetComponent<MeshFilter>().mesh;
        // bounds = mesh.bounds; // 不能放到这里的，放在这里的话，每帧打印的都是同一个bounds；就算是rend.bounds，打印结果也不变
    }

    // Update is called once per frame
    void Update()
    {
        bounds = mesh.bounds; // 应该实时获取
        print(bounds.center);
    }
}

结果：

Render.bounds

Unity - Scripting API: Renderer.bounds (unity3d.com)

主要是这么几句：

试一试

代码：

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

public class BoundTest : MonoBehaviour
{
    private Mesh mesh;
    private Renderer rend;

    private Bounds bounds;

    // Start is called before the first frame update
    void Start()
    {
        mesh = GetComponent<MeshFilter>().mesh;
        rend = GetComponent<Renderer>();
    }

    // Update is called once per frame
    void Update()
    {
        //bounds = mesh.bounds;
        bounds = rend.bounds; // 实时获取包围盒，才能看到变没变

        print(bounds.center);
    }
}