smart-bow-infrared/Assets/BowArrow/Scripts/Game/TargetDistanceLabel.cs

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.UI;
/* 靶子距离标签（在靶子头顶） */
public class TargetDistanceLabel : MonoBehaviour
{
    public RectTransform canvasRTF;
    public Transform followTarget;
    TargetBody targetBody;
    Vector3 centerPoint = new Vector3(0.5f, 0.5f, 0);
    Text textComp;
    Canvas parentCanvas; 

    void Start()
    {
        targetBody = GameObject.Find("GameArea/TargetObject").GetComponentInChildren<TargetBody>();
        textComp = this.GetComponent<Text>();
        parentCanvas = transform.parent.GetComponent<Canvas>();
    }
    void LateUpdate()
    {
        Camera mainCamera = BowCamera.ins.GetRenderCamera();
        parentCanvas.worldCamera = mainCamera;
        float angle = Vector3.Angle(mainCamera.transform.forward, followTarget.position - mainCamera.transform.position);
        if (angle > 90) {
            textComp.enabled = false;
            return;
        } else {
            textComp.enabled = true;
        }
        Vector3 v3 = mainCamera.WorldToViewportPoint(followTarget.position) - centerPoint;
        v3.x *= canvasRTF.rect.width;
        v3.y *= canvasRTF.rect.height;
        v3.z = 0;
        this.transform.localPosition = v3;
        textComp.text = ((int)Mathf.Round(targetBody.GetDistance())) + "M";
    }
}