Unity3d 使用Gizmos画一个圆圈

Gizmos是场景视图里的一个可视化调试工具。

在做项目过程中。我们常常会用到它，比如：绘制一条射线等。

Unity3D 4.2版本号截至。眼下仅仅提供了绘制射线，线段，网格球体，实体球体，网格立方体，实体立方体，图标。GUI纹理，以及摄像机线框。

假设须要绘制一个圆环还须要自己写代码

using UnityEngine;
using System;
public class HeGizmosCircle : MonoBehaviour
{
       public Transform m_Transform;
       public float m_Radius = 1; // 圆环的半径
       public float m_Theta = 0.1f; // 值越低圆环越平滑
       public Color m_Color = Color.green; // 线框颜色
       
       void Start()
       {
              if (m_Transform == null)
              {
                     throw new Exception("Transform is NULL.");
              }
       }
       void OnDrawGizmos()
       {
              if (m_Transform == null) return;
              if (m_Theta < 0.0001f) m_Theta = 0.0001f;
              // 设置矩阵
              Matrix4x4 defaultMatrix = Gizmos.matrix;
              Gizmos.matrix = m_Transform.localToWorldMatrix;
              // 设置颜色
              Color defaultColor = Gizmos.color;
              Gizmos.color = m_Color;
              // 绘制圆环
              Vector3 beginPoint = Vector3.zero;
              Vector3 firstPoint = Vector3.zero;
              for (float theta = 0; theta < 2 * Mathf.PI; theta += m_Theta)
              {
                     float x = m_Radius * Mathf.Cos(theta);
                     float z = m_Radius * Mathf.Sin(theta);
                     Vector3 endPoint = new Vector3(x, 0, z);
                     if (theta == 0)
                     {
                            firstPoint = endPoint;
                     }
                     else
                     {
                            Gizmos.DrawLine(beginPoint, endPoint);
                     }
                     beginPoint = endPoint;
              }
              // 绘制最后一条线段
              Gizmos.DrawLine(firstPoint, beginPoint);
              // 恢复默认颜色
              Gizmos.color = defaultColor;
              // 恢复默认矩阵
              Gizmos.matrix = defaultMatrix;
       }
}

把代码拖到一个GameObject上，关联该GameObject的Transform，然后就能够在Scene视图窗体里显示一个圆了。

通过调整Transform的Position。Rotation。Scale，来调整圆的位置，旋转，缩放。

补充：基于Unity3D使用LineRender组件绘制圆线

在此记录一下使用Unity3D 的LineRender绘制线的过程，经过测试LineRender与OpenGL的GL_LINE_STRIP绘制方式一样，因此计算完点之后需要把起始点即为终点，多算一个点才算闭合。

代码如下：

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.UI; 
public class DrawLines: MonoBehaviour
{
    public float m_radius = 1.0f;
    public Material m_material;
    public float m_lineWidth = 1.0f;
    private List<Vector3> vPath = new List<Vector3>();
    // Start is called before the first frame update
    void Start()
    {
        int count = 60;
       for (int i=1; i<= (count+1); i++)
        {
            if(i == (count+1))
            {
                float x = Mathf.Cos(2 * Mathf.PI / count) * m_radius;
                float y = transform.localPosition.y;
                float z = Mathf.Sin(2 * Mathf.PI / count) * m_radius;
                vPath.Add(new Vector3(x, y, z));
            }
            else
            {
                float x = Mathf.Cos(2 * Mathf.PI / count * i) * m_radius;
                float y = transform.localPosition.y;
                float z = Mathf.Sin(2 * Mathf.PI / count * i) * m_radius;
                vPath.Add(new Vector3(x, y, z));
            } 
        } 
        GameObject lineGroup = new GameObject("LineGroup");
        GameObject lineObject = new GameObject("RadarLine");
        LineRenderer line = lineObject.AddComponent<LineRenderer>();
        line.material = m_material;
        line.useWorldSpace = false;
        line.positionCount = vPath.Count;
        line.startWidth = m_lineWidth;
        line.endWidth = m_lineWidth;
        line.SetPositions(vPath.ToArray()); 
    } 
    // Update is called once per frame
    void Update()
    {        
    }
}

运行一下看一下效果：

以上为个人经验，希望能给大家一个参考，也希望大家多多支持猪先飞。如有错误或未考虑完全的地方，望不吝赐教。