Android OpenGL学习笔记

大家好，今天我讲一下Android OpenGL，这个系列是我的学习笔记，希望对大家有所帮助！这一节将给大家简洁的介绍一下术语，以及第一个Android OpenGL程序.

首先让我看们看一下术语:

Vertex (顶点)
A vertex is a point in 3D space and is the building block for many objects. In OpenGL you can specify as few as two coordinates (X,Y) and as many as four (X,Y,Z,W). The w-axis is optional, the default value is set to 1.0. The z-axis is also optional, the default value is set to 0. In this series, we will use the three main coordinates X, Y, and Z, since the W is generally used as a placeholder. The plural of vertex is vertices (mainly important for non native speakers, because it may create confusion). All objects are drawn using vertices as their points, so a point will refer to a vertex.

Triangle (三角)
A triangle requires three points to be created. So in OpenGL, we use three vertices to create one.

Polygon (多边形)
A polygon is an object which has at least three connected points. Therefor a triangle is also a polygon.

Primitives (基本实体)
A primitive is a three-dimensional object created using either triangles or polygons. A bit ironic: A detailed model with 50.000 vertices is also a primitive like a low detailed model with 500 vertices.

下面就是我们的第一个Android OpenGL程序:

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1. package  com.android.tutor;  
2. import  android.app.Activity;  
3. import  android.opengl.GLSurfaceView;  
4. import  android.os.Bundle;  
5. public   class  OpenGl_Lesson1  extends  Activity {  
6.     public   void  onCreate(Bundle savedInstanceState) {  
7.         super .onCreate(savedInstanceState);  
8.           
9.         GLSurfaceView mGlSurfaceView = new  GLSurfaceView( this );  
10.           
11.          
12.         mGlSurfaceView.setRenderer(new  OpenGLRender());  
13.         setContentView(mGlSurfaceView);  
14.           
15.     }  
16. }  

package com.android.tutor; import android.app.Activity; import android.opengl.GLSurfaceView; import android.os.Bundle; public class OpenGl_Lesson1 extends Activity { public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); GLSurfaceView mGlSurfaceView = new GLSurfaceView(this); mGlSurfaceView.setRenderer(new OpenGLRender()); setContentView(mGlSurfaceView); } }

我们这里的View是用的GLSurfaceView,但是它要setRenderer()一下，就像我们Activity里面的setContentView()方法一样!

这里的OpenGLRender是我重新写的类，它继承于GLSurfaceView.Renderer,我们要实现其种的三个方法:

onSurfaceCreated(),onSurfaceChanged(),onDrawFrame()。代码如下:

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1. package  com.android.tutor;  
2. import  javax.microedition.khronos.egl.EGLConfig;  
3. import  javax.microedition.khronos.opengles.GL10;  
4. import  android.opengl.GLSurfaceView.Renderer;  
5. public   class  OpenGLRender  implements  Renderer {  
6.     @Override   
7.     public   void  onSurfaceCreated(GL10 gl, EGLConfig config) {  
8.         // TODO Auto-generated method stub   
9.           
10.         gl.glClearColor(0 .9f,  0 .2f,  0 .2f,  1 .0f);  
11.         gl.glClear(GL10.GL_COLOR_BUFFER_BIT);  
12.     }  
13.     @Override   
14.     public   void  onSurfaceChanged(GL10 gl,  int  width,  int  height) {  
15.         gl.glViewport(0 ,  0 , width, height);  
16.     }  
17.     @Override   
18.     public   void  onDrawFrame(GL10 gl) {  
19.         // TODO Auto-generated method stub   
20.     }  
21.       
22. }  

package com.android.tutor; import javax.microedition.khronos.egl.EGLConfig; import javax.microedition.khronos.opengles.GL10; import android.opengl.GLSurfaceView.Renderer; public class OpenGLRender implements Renderer { @Override public void onSurfaceCreated(GL10 gl, EGLConfig config) { // TODO Auto-generated method stub gl.glClearColor(0.9f, 0.2f, 0.2f, 1.0f); gl.glClear(GL10.GL_COLOR_BUFFER_BIT); } @Override public void onSurfaceChanged(GL10 gl, int width, int height) { gl.glViewport(0, 0, width, height); } @Override public void onDrawFrame(GL10 gl) { // TODO Auto-generated method stub } }

 第10行就是相当于我们设置画布颜色RGBA(红绿蓝透)，第11行这里是清除深度颜色缓存，不加上一句，第10句不起作用，整个View的颜色

还是黑黑的！

运行效果如下:

 

 

 

 

前面讲了一些Android OpenGl 的概念问题，这一节讲给大家讲一下如何画一个三角现出来.

一、新建一个Android工程命名为:OpenGL_Lesson2.

二、修改OpenGL_Lesson2.java代码如下:

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1. package  com.android.tutor;  
2. import  android.app.Activity;  
3. import  android.os.Bundle;  
4. public   class  OpenGL_Lesson2  extends  Activity {  
5.      
6.     private  OpenGlView mOpenGlView;  
7.     public   void  onCreate(Bundle savedInstanceState) {  
8.         super .onCreate(savedInstanceState);  
9.         
10.         mOpenGlView = new  OpenGlView( this );  
11.         setContentView(mOpenGlView);  
12.                 
13.     }  
14. }  

package com.android.tutor; import android.app.Activity; import android.os.Bundle; public class OpenGL_Lesson2 extends Activity { private OpenGlView mOpenGlView; public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); mOpenGlView = new OpenGlView(this); setContentView(mOpenGlView); } }

三、新建一个类OpenGlView.java继承与GLSurfaceView,代码如下:

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1. package  com.android.tutor;  
2. import  android.content.Context;  
3. import  android.opengl.GLSurfaceView;  
4. public   class  OpenGlView  extends  GLSurfaceView {  
5.       
6.     private  OpenGlRender mOpenGlRender;  
7.     public  OpenGlView(Context context) {  
8.         super (context);  
9.         mOpenGlRender = new  OpenGlRender();  
10.         setRenderer(mOpenGlRender);  
11.     }  
12.       
13.       
14.       
15. }  

package com.android.tutor; import android.content.Context; import android.opengl.GLSurfaceView; public class OpenGlView extends GLSurfaceView { private OpenGlRender mOpenGlRender; public OpenGlView(Context context) { super(context); mOpenGlRender = new OpenGlRender(); setRenderer(mOpenGlRender); } }

四、新建一个OpenGlRender.java类继承与Renderer,代码如下:

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1. package  com.android.tutor;  
2. import  java.nio.ByteBuffer;  
3. import  java.nio.ByteOrder;  
4. import  java.nio.FloatBuffer;  
5. import  java.nio.ShortBuffer;  
6. import  javax.microedition.khronos.egl.EGLConfig;  
7. import  javax.microedition.khronos.opengles.GL10;  
8. import  android.opengl.GLSurfaceView.Renderer;  
9. public   class  OpenGlRender  implements  Renderer {  
10.       
11.     private   float  _red = 0f;  
12.     private   float  _green = 25f;  
13.     private   float  _blue = 200f;  
14.       
15.     private  ShortBuffer _indexBuffer;  
16.       
17.     private  FloatBuffer _vertexBuffer;  
18.       
19.       
20.     private   short [] _indicesArray = { 0 ,  1 ,  2 };  
21.     private   int  _nrOfVertices =  3 ;  
22.     @Override   
23.     public   void  onSurfaceCreated(GL10 gl, EGLConfig config) {  
24.           
25.         gl.glEnableClientState(GL10.GL_VERTEX_ARRAY);  
26.         initTriangle();  
27.     }  
28.     @Override   
29.     public   void  onSurfaceChanged(GL10 gl,  int  width,  int  height) {  
30.           
31.         gl.glViewport(0 ,  0 , width, height);  
32.     }  
33.   
34.       
35.     @Override   
36.     public   void  onDrawFrame(GL10 gl) {  
37.         gl.glClearColor(_red, _green, _blue, 1 .0f);  
38.           
39.         gl.glClear(GL10.GL_COLOR_BUFFER_BIT);  
40.           
41.          gl.glColor4f(0 .5f, 0f, 0f,  0 .5f);  
42.          gl.glVertexPointer(_nrOfVertices, GL10.GL_FLOAT, 0 , _vertexBuffer);  
43.          gl.glDrawElements(GL10.GL_TRIANGLES, _nrOfVertices, GL10.GL_UNSIGNED_SHORT, _indexBuffer);  
44.     }  
45.       
46.     private   void  initTriangle() {  
47.         // float has 4 bytes   
48.         ByteBuffer vbb = ByteBuffer.allocateDirect(_nrOfVertices * 3  *  4 );  
49.         vbb.order(ByteOrder.nativeOrder());  
50.         _vertexBuffer = vbb.asFloatBuffer();  
51.           
52.         // short has 4 bytes   
53.         ByteBuffer ibb = ByteBuffer.allocateDirect(_nrOfVertices * 2 );  
54.         ibb.order(ByteOrder.nativeOrder());  
55.         _indexBuffer = ibb.asShortBuffer();  
56.           
57.         float [] coords = {  
58.             -0 .5f, - 0 .5f, 0f,  // (x1, y1, z1)   
59.             0 .5f, - 0 .5f, 0f,  // (x2, y2, z2)   
60.             0f, 0 .5f, 0f  // (x3, y3, z3)   
61.         };  
62.           
63.         _vertexBuffer.put(coords);  
64.           
65.         _indexBuffer.put(_indicesArray);  
66.           
67.         _vertexBuffer.position(0 );  
68.         _indexBuffer.position(0 );  
69.     }  
70. }  

package com.android.tutor; import java.nio.ByteBuffer; import java.nio.ByteOrder; import java.nio.FloatBuffer; import java.nio.ShortBuffer; import javax.microedition.khronos.egl.EGLConfig; import javax.microedition.khronos.opengles.GL10; import android.opengl.GLSurfaceView.Renderer; public class OpenGlRender implements Renderer { private float _red = 0f; private float _green = 25f; private float _blue = 200f; private ShortBuffer _indexBuffer; private FloatBuffer _vertexBuffer; private short[] _indicesArray = {0, 1, 2}; private int _nrOfVertices = 3; @Override public void onSurfaceCreated(GL10 gl, EGLConfig config) { gl.glEnableClientState(GL10.GL_VERTEX_ARRAY); initTriangle(); } @Override public void onSurfaceChanged(GL10 gl, int width, int height) { gl.glViewport(0, 0, width, height); } @Override public void onDrawFrame(GL10 gl) { gl.glClearColor(_red, _green, _blue, 1.0f); gl.glClear(GL10.GL_COLOR_BUFFER_BIT); gl.glColor4f(0.5f, 0f, 0f, 0.5f); gl.glVertexPointer(_nrOfVertices, GL10.GL_FLOAT, 0, _vertexBuffer); gl.glDrawElements(GL10.GL_TRIANGLES, _nrOfVertices, GL10.GL_UNSIGNED_SHORT, _indexBuffer); } private void initTriangle() { // float has 4 bytes ByteBuffer vbb = ByteBuffer.allocateDirect(_nrOfVertices * 3 * 4); vbb.order(ByteOrder.nativeOrder()); _vertexBuffer = vbb.asFloatBuffer(); // short has 4 bytes ByteBuffer ibb = ByteBuffer.allocateDirect(_nrOfVertices * 2); ibb.order(ByteOrder.nativeOrder()); _indexBuffer = ibb.asShortBuffer(); float[] coords = { -0.5f, -0.5f, 0f, // (x1, y1, z1) 0.5f, -0.5f, 0f, // (x2, y2, z2) 0f, 0.5f, 0f // (x3, y3, z3) }; _vertexBuffer.put(coords); _indexBuffer.put(_indicesArray); _vertexBuffer.position(0); _indexBuffer.position(0); } }

五、运行之，效果如下:

今天晚上就先不做详细解释了！改日在加上！谢谢~