最近做項目的時候，有一個需要從攝像機發出一條射線，當射線檢測到有碰撞物體的時候，點擊鼠標左鍵開始畫線。我是創立了一個平板drawing，當然Cube什么的也是可以的。
c#腳本代碼，將這個腳本拖到攝像機里，然后拖拽材質到畫線材質，拖拽碰撞體到腳本那里即可以。
代碼腳本（附有注釋）：
<pre><code>
using UnityEngine;
using System.Collections;
public class test : MonoBehaviour {
//-----------劃線所能夠用到材質
public Material lineMaterial ;
//
int maxPoints = 5000;
//全局變量的定義方法
public static float lineWidth = 4.0f;
int minPixelMove = 2; // Must move at least this many pixels per sample for a new segment to be recorded
public Vector2[] linePoints;
private VectorLine line ;
private int lineIndex = 0;
private Vector2 previousPosition;
private int sqrMinPixelMove ;
private bool canDraw = false;
//記錄當下畫板的位置，判斷平板是否平移等
public Vector3 boardPosition;
public GameObject board;
//記錄當下畫板的大小，判斷畫板是否縮放等
public Vector3 boardScale;
//初始化平板的大小與位置
void IntializeScaleAndPosition()
{
boardPosition=Camera.mainCamera.WorldToScreenPoint(board.transform.position);
boardScale=board.transform.localScale;
}
// 初始化
void Start () {
linePoints = new Vector2[maxPoints];
line = new VectorLine("DrawnLine", linePoints,lineMaterial, lineWidth, LineType.Continuous);
sqrMinPixelMove = minPixelMove * minPixelMove;
IntializeScaleAndPosition();
}
// Update is called once per frame
void Update () {
Vector2 mousePos = Input.mousePosition;
//當畫板移動時，將所有的點按照統一方向移動相同的距離
//當前畫板的位置
Vector3 currentBoardPositon=Camera.mainCamera.WorldToScreenPoint(board.transform.position);
//畫板的移動距離
Vector3 moveDistance=currentBoardPositon-boardPosition;
if(moveDistance.x!=0||moveDistance.y!=0)
{
//將所有的畫下的點都平移
for(int i=0;i<linePoints.Length;i++)
{
Vector2 dis=new Vector2(moveDistance.x,moveDistance.y);
linePoints[i]+=dis;
}
//銷毀當前畫下的線
Vector.DestroyLine(ref line);
//距離平移后，所有的點的位置已經重新獲得，重新畫下新的線
line = new VectorLine("DrawnLine", linePoints, lineMaterial, lineWidth, LineType.Continuous);
line.minDrawIndex = 1;
line.maxDrawIndex = lineIndex;
Vector.DrawLine(line);
}
boardPosition=Camera.mainCamera.WorldToScreenPoint(board.transform.position);
//平板的縮放操作，對平板進行縮放，同時畫出的線也要能夠實現縮放。
//檢測平板是否已經開始縮放
float currentScale=board.transform.localScale.x;
float scaleFactor=currentScale/(boardScale.x);
//Debug.Log("scaleFactor "+scaleFactor+" currentScale "+currentScale+" boardScale "+boardScale.x);
boardScale=board.transform.localScale;
if(scaleFactor!=1||scaleFactor!=1)
{
// 求出畫板中心的位置
Vector3 boardPostionToSceern=Camera.mainCamera.WorldToScreenPoint(board.transform.position);
//當平板縮放時，所有的點都要同比例縮放。
for(int i=0;i<linePoints.Length;i++)
{
Vector3 pointPositon=new Vector3(linePoints[i].x,linePoints[i].y,0);
Vector3 PointToCenterDistance=(pointPositon-boardPostionToSceern)*scaleFactor;
linePoints[i]=new Vector2((boardPostionToSceern+PointToCenterDistance).x,(boardPostionToSceern+PointToCenterDistance).y);
}
//銷毀當前畫下的線
Vector.DestroyLine(ref line);
//畫板縮放后，所有的點的位置已經重新獲得，重新畫下新的線
line = new VectorLine("DrawnLine", linePoints, lineMaterial, lineWidth, LineType.Continuous);
line.minDrawIndex = 1;
line.maxDrawIndex = lineIndex;
Vector.DrawLine(line);
}
//從攝像頭發出一條射線
Ray ray=Camera.mainCamera.ScreenPointToRay(Input.mousePosition);
RaycastHit hit;
if(Physics.Raycast(ray,out hit,1000))
{
//檢測到物體時才開始畫
if(hit.transform.gameObject.name=="drawing")
{
if (Input.GetMouseButtonDown(0))
{
// Vector.ZeroPointsInLine(line);
// line.minDrawIndex = lineIndex;
// Vector.DrawLine(line);
// linePoints[lineIndex] = mousePos;
previousPosition = mousePos;
lineIndex++;
linePoints[lineIndex] = mousePos;
canDraw = true;
}
else if (Input.GetMouseButton(0) && (mousePos - previousPosition).sqrMagnitude > sqrMinPixelMove && canDraw)
{
previousPosition = linePoints[++lineIndex] = mousePos;
line.minDrawIndex = lineIndex - 1;
line.maxDrawIndex = lineIndex;
if (lineIndex >= maxPoints - 1) canDraw = false;
Vector.DrawLine(line);
}
}
}
</code></pre>
