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(BundlesavedInstanceState){
7. super .onCreate(savedInstanceState);
9. GLSurfaceViewmGlSurfaceView=new GLSurfaceView( this );
12. mGlSurfaceView.setRenderer(new OpenGLRender());
13. setContentView(mGlSurfaceView);
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(GL10gl,EGLConfigconfig){
8. //TODOAuto-generatedmethodstub
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(GL10gl, int width, int height){
15. gl.glViewport(0 , 0 ,width,height);
16. }
17. @Override
18. public void onDrawFrame(GL10gl){
19. //TODOAuto-generatedmethodstub
20. }
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{
6. private OpenGlViewmOpenGlView;
7. public void onCreate(BundlesavedInstanceState){
8. super .onCreate(savedInstanceState);
10. mOpenGlView=new OpenGlView( this );
11. setContentView(mOpenGlView);
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{
6. private OpenGlRendermOpenGlRender;
7. public OpenGlView(Contextcontext){
8. super (context);
9. mOpenGlRender=new OpenGlRender();
10. setRenderer(mOpenGlRender);
11. }
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{
11. private float _red=0f;
12. private float _green=25f;
13. private float _blue=200f;
15. private ShortBuffer_indexBuffer;
17. private FloatBuffer_vertexBuffer;
20. private short []_indicesArray={ 0 , 1 , 2 };
21. private int _nrOfVertices= 3 ;
22. @Override
23. public void onSurfaceCreated(GL10gl,EGLConfigconfig){
25. gl.glEnableClientState(GL10.GL_VERTEX_ARRAY);
26. initTriangle();
27. }
28. @Override
29. public void onSurfaceChanged(GL10gl, int width, int height){
31. gl.glViewport(0 , 0 ,width,height);
32. }
35. @Override
36. public void onDrawFrame(GL10gl){
37. gl.glClearColor(_red,_green,_blue,1 .0f);
39. gl.glClear(GL10.GL_COLOR_BUFFER_BIT);
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. }
46. private void initTriangle(){
47. //floathas4bytes
48. ByteBuffervbb=ByteBuffer.allocateDirect(_nrOfVertices*3 * 4 );
49. vbb.order(ByteOrder.nativeOrder());
50. _vertexBuffer=vbb.asFloatBuffer();
52. //shorthas4bytes
53. ByteBufferibb=ByteBuffer.allocateDirect(_nrOfVertices*2 );
54. ibb.order(ByteOrder.nativeOrder());
55. _indexBuffer=ibb.asShortBuffer();
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. };
63. _vertexBuffer.put(coords);
65. _indexBuffer.put(_indicesArray);
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~