编辑器扩展 - Scene视图

扩展Scene视图的几种方式

1) 注册SceneView.duringSceneGui委托（Unity2018及之前版本是SceneView.onSceneGUIDelegate）

#if UNITY_EDITOR

using UnityEditor;

public class TestSceneGUIWindow : EditorWindow
{
    [MenuItem("MyTools/TestSceneGUIWindow")]
    public static void ShowWindow()
    {
        EditorWindow.GetWindow<TestSceneGUIWindow>(false, "TestSceneGUIWindow", true).Show();
    }

    private void OnEnable()
    {
        SceneView.onSceneGUIDelegate -= OnMySceneGUI;
        SceneView.onSceneGUIDelegate += OnMySceneGUI;
    }

    private void OnDisable()
    {
        SceneView.onSceneGUIDelegate -= OnMySceneGUI;
    }

    private void OnMySceneGUI(SceneView sceneView)
    {
        //在这边扩展Scene视图
    }

}

#endif

2) 自定义Editor，然后实现事件函数OnSceneGUI

#if UNITY_EDITOR

using UnityEditor;

[CustomEditor(typeof(Xxx))]
public class TestSceneGUIEditor : Editor
{

    private void OnSceneGUI()
    {
        //在这边扩展Scene视图
    }

}

#endif

显示gui控件

GUILayout.BeginArea(new Rect(40, 20, 200, 200), "test");
if (GUILayout.Button("Button"))
{
    Debug.Log($"Button Click");
}
EditorGUILayout.Space();
GUILayout.BeginHorizontal();
{
    EditorGUILayout.SelectableLabel("Num:", GUILayout.Width(35));
    EditorGUILayout.IntField(0);
}
GUILayout.EndHorizontal();
EditorGUILayout.HelpBox("一些提示信息", MessageType.Warning);
EditorGUILayout.IntSlider(0, 0, 10);

GUILayout.EndArea();

显示几何形状

弧形

var arcRadius = 5;
var arcAngle = 270;

Handles.color = Color.red;
var pos = new Vector3(3, 0, 0);
var arcStartDir = new Vector3(0, 0, 1);
Handles.DrawSolidArc(pos, Vector3.up, arcStartDir, arcAngle, arcRadius); //x-z平面绘制2d弧形, 90度开始, 顺时针绘制270度

Handles.color = Color.green;
pos.y += 5;
arcStartDir = new Vector3(1, 0, 0);
Handles.DrawSolidArc(pos, Vector3.up, arcStartDir, arcAngle, arcRadius); //x-z平面绘制2d弧形, 0度开始, 顺时针绘制270度

Handles.color = Color.blue;
pos.y += 5;
arcStartDir = new Vector3(1, 0, 1);
Handles.DrawSolidArc(pos, Vector3.up, arcStartDir, arcAngle, arcRadius); //x-z平面绘制2d弧形, 45度开始, 顺时针绘制270度

Handles.color = Color.cyan;
pos.y += 5;
arcStartDir = new Vector3(1, 1, 0);
Handles.DrawSolidArc(pos, Vector3.up, arcStartDir, arcAngle, arcRadius); //3d弧形, 相当于绿色的那个弧形向上拉起一点(从顶往下看, 和它是重叠的)

直线，折线

Handles.color = Color.red;
var pos = new Vector3(0, 0, 0);
Handles.DrawLine(pos, new Vector3(10, 10, 10)); //绘制直线(红色)

Handles.color = Color.blue;
var points = new Vector3[] { Vector3.zero, new Vector3(10, 10, -10), new Vector3(10, -10, -10) };
Handles.DrawPolyLine(points); //绘制折线(蓝色)

Handles.color = Color.green;
points = new Vector3[] { Vector3.zero, new Vector3(10, -10, 10), new Vector3(-10, -10, 10) };
Handles.DrawAAPolyLine(5, points); //宽度为5的折线(绿色, 抗锯齿)

显示操控控件

m_Position = Handles.PositionHandle(m_Position, Quaternion.identity);

var pos = new Vector3(6, 0, 0);

Handles.color = Color.red;
Handles.Label(pos, $"文本");

float handleSize = HandleUtility.GetHandleSize(pos);
EditorGUI.BeginChangeCheck();
pos.x += 3;
m_Scale = Handles.ScaleHandle(m_Scale, pos, Quaternion.identity, handleSize);

pos.x += 10;
m_Rot = Handles.RotationHandle(m_Rot, pos); //Handles.DoRotationHandle(m_Rot, pos);

pos.x += 10;
m_Rot = Handles.FreeRotateHandle(m_Rot, pos, handleSize);

pos.x += 8;
m_Radius = Handles.RadiusHandle(Quaternion.identity, pos, m_Radius);

if (EditorGUI.EndChangeCheck())
{
    Debug.Log($"{m_Scale}, {m_Position}, {m_Rot}, {m_Radius}");
}

参考 

UnityEditor学习笔记二 - Wunsam_Chan - 博客园 (cnblogs.com)

Unity3d Editor 编辑器扩展功能详解（5）Handles - 知乎 (zhihu.com)