我们分两种情况，一种是UI上连线，一种是世界坐标下连线。

UI用

效果图

UI代码示例

public class DrawLine : MonoBehaviour
{
    
    
    [Header("Point")]
    public RectTransform startPoint;//起始点，UI用
    public RectTransform endPoint;//终点，UI用
    public GameObject linePrefab;//一个空物体下挂一个SpriteRender就行了
    public float lineWidth;//线的宽度
    private GameObject m_line;//线的实例
    private RectTransform m_rect;
    private RectTransform m_lineRect;
    private void Awake()
    {
    
    
        m_rect = GetComponent<RectTransform>();
    }
    private void Start()
    {
    
    
        m_line = CreateLine(m_rect.anchoredPosition, endPoint.anchoredPosition);
        //下方UI要加，世界坐标下不需要
        //不明白函数意思看文档，作用是防止线段遮挡视野（层级不同可能会遮挡）
        m_line.transform.SetAsFirstSibling();
    }
    private void Update()
    {
    
    
        DrawStraightLine(m_line, m_rect.anchoredPosition, endPoint.anchoredPosition);
    }
    /// <summary>
    /// 创建一条两点之间的线
    /// </summary>
    /// <param name="startPoint">起始点</param>
    /// <param name="endPoint">结束点</param>
    public GameObject CreateLine(Vector2 startPoint, Vector2 endPoint)
    {
    
    
        GameObject line = Instantiate(linePrefab, transform.parent);
        m_lineRect = line.GetComponent<RectTransform>();
        return line;
    }
    //划线功能
    private void DrawStraightLine(GameObject line, Vector2 a, Vector2 b)
    {
    
    
        float distance = Vector2.Distance(a, b);                                    //求距离
        float angle = Vector2.SignedAngle(a - b, Vector2.left);                     //求夹角
        line.GetComponent<RectTransform>().anchoredPosition = (a + b) / 2;
        line.GetComponent<RectTransform>().sizeDelta = new Vector2(distance, lineWidth);   //长度，宽度
        line.transform.localRotation = Quaternion.AngleAxis(-angle, Vector3.forward);
    }

}

挂载示例

世界坐标用

挂载示例

简单一点的方法是直接用Unity自带的Line Renderer
在一个游戏对象上挂载Line Renderer

效果图

世界坐标代码示例

public class LineRendererText : MonoBehaviour
{
    
    
    public Transform startPoint;
    public Transform endPoint;
    private LineRenderer m_lineRenderer;
    private void Awake()
    {
    
    
        m_lineRenderer = GetComponent<LineRenderer>();
    }
    private void Update()
    {
    
    
        m_lineRenderer.SetPosition(0, startPoint.position);
        m_lineRenderer.SetPosition(1, endPoint.position);
    }
}