Unity3D 使用 GL 绘制线条

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在前两篇中，我们使用了 Graphics（查看详情）以及 Line Renderer 方法绘制线条（查看详情），这次我们通过 GL 来绘制线条，这种方法与前两种方法相比，效率与性能上面差不多。原文链接：http://www.everyday3d.com/blog/index.php/2010/03/15/3-ways-to-draw-3d-lines-in-unity3d/。

新建立一个 C# 脚本，取名：DrawLinesByGL.cs 代码如下：

001 using UnityEngine;
002 using System.Collections;
003
004 public class DrawLinesByGL : MonoBehaviour
005 {
006     public Shader shader;
007
008     private static Material m;
009     private GameObject g;
010     private float speed = 100.0f;
011     private Vector3[] lp;
012     private Vector3[] sp;
013     private Vector3 s;
014
015     private GUIStyle labelStyle;
016     private GUIStyle linkStyle;
017
018     void Start () {
019         labelStyle = new GUIStyle();
020         labelStyle.normal.textColor = Color.black;
021
022         linkStyle = new GUIStyle();
023         linkStyle.normal.textColor = Color.blue;
024
025         m = new Material(shader);
026         g = new GameObject("g");
027         lp = new Vector3[0];
028         sp = new Vector3[0];
029     }
030
031     void processInput() {
032         float s = speed * Time.deltaTime;
033         if(Input.GetKey(KeyCode.RightShift) || Input.GetKey(KeyCode.LeftShift)) s = s * 0.1f;
034         if(Input.GetKey(KeyCode.UpArrow)) g.transform.Rotate(-s, 0, 0);
035         if(Input.GetKey(KeyCode.DownArrow)) g.transform.Rotate(s, 0, 0);
036         if(Input.GetKey(KeyCode.LeftArrow)) g.transform.Rotate(0, -s, 0);
037         if(Input.GetKey(KeyCode.RightArrow)) g.transform.Rotate(0, s, 0);
038
039         if(Input.GetKeyDown(KeyCode.C)) {
040             g.transform.rotation = Quaternion.identity;
041             lp = new Vector3[0];
042             sp = new Vector3[0];
043         }
044     }
045
046     void Update() {
047         processInput();
048
049         if(Input.GetMouseButton(0)) {
050
051             Vector3 e = GetNewPoint();
052
053             if(s != Vector3.zero) {
054                 for(int i = 0; i < lp.Length; i += 2) {
055                     float d = Vector3.Distance(lp[i], e);
056                     if(d < 1 && Random.value > 0.9f) sp = AddLine(sp, lp[i], e, false);
057                 }
058
059                 lp = AddLine(lp, s, e, false);
060             }
061
062             s = e;
063         } else {
064             s = Vector3.zero;
065         }
066     }
067
068     void Update1() {
069         processInput();
070
071         Vector3 e;
072
073         if(Input.GetMouseButtonDown(0)) {
074             s = GetNewPoint();
075         }
076
077         if(Input.GetMouseButton(0)) {
078             e = GetNewPoint();
079             lp = AddLine(lp, s, e, true);
080         }
081
082         if(Input.GetMouseButtonUp(0)) {
083             e = GetNewPoint();
084             lp = AddLine(lp, s, e, false);
085         }
086     }
087
088     Vector3[] AddLine(Vector3[] l, Vector3 s, Vector3 e, bool tmp) {
089         int vl = l.Length;
090         if(!tmp || vl == 0) l = resizeVertices(l, 2);
091         else vl -= 2;
092
093         l[vl] = s;
094         l[vl+1] = e;
095         return l;
096     }
097
098     Vector3[] resizeVertices(Vector3[] ovs, int ns) {
099         Vector3[] nvs = new Vector3[ovs.Length + ns];
100         for(int i = 0; i < ovs.Length; i++) nvs[i] = ovs[i];
101         return nvs;
102     }
103
104     Vector3 GetNewPoint() {
105         return g.transform.InverseTransformPoint(
106             Camera.main.ScreenToWorldPoint(
107                 new Vector3(Input.mousePosition.x, Input.mousePosition.y, Camera.main.transform.position.z * -1.0f)
108             )
109         );
110     }
111
112     void OnPostRender() {
113         m.SetPass(0);
114         GL.PushMatrix();
115         GL.MultMatrix(g.transform.transform.localToWorldMatrix);
116         GL.Begin( GL.LINES );
117         GL.Color( new Color(0,0,0,0.4f) );
118
119         for(int i = 0; i < lp.Length; i++) {
120             GL.Vertex3(lp[i].x, lp[i].y, lp[i].z);
121         }
122
123         GL.Color( new Color(0,0,0,0.1f) );
124
125         for(int i = 0; i < sp.Length; i++) {
126             GL.Vertex3(sp[i].x, sp[i].y, sp[i].z);
127         }
128
129         GL.End();
130         GL.PopMatrix();
131     }
132
133     void OnGUI() {
134         GUI.Label (new Rect (10, 10, 300, 24), "GL. Cursor keys to rotate (with Shift for slow)", labelStyle);
135         int vc = lp.Length + sp.Length;
136         GUI.Label (new Rect (10, 26, 300, 24), "Pushing " + vc + " vertices. 'C' to clear", labelStyle);
137
138         GUI.Label (new Rect (10, Screen.height - 20, 250, 24), ".Inspired by a demo from ", labelStyle);
139         if(GUI.Button (new Rect (150, Screen.height - 20, 300, 24), "mrdoob", linkStyle)) {
140             Application.OpenURL("http://mrdoob.com/lab/javascript/harmony/");
141         }
142     }
143 }

然后把 DrawLinesByGL.cs 组件挂载到 MainCamera 对象上，如图：

运行游戏，最终效果如图：

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