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:

 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(BundlesavedInstanceState){
 super .onCreate(savedInstanceState);

 GLSurfaceViewmGlSurfaceView=new GLSurfaceView( this );


 mGlSurfaceView.setRenderer(new OpenGLRender());
 setContentView(mGlSurfaceView);

 }
 }

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:

 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(GL10gl,EGLConfigconfig){
 //TODOAuto-generatedmethodstub

 gl.glClearColor(0 .9f, 0 .2f, 0 .2f, 1 .0f);
 gl.glClear(GL10.GL_COLOR_BUFFER_BIT);
 }
 @Override
 public  void onSurfaceChanged(GL10gl, int width, int height){
 gl.glViewport(0 , 0 ,width,height);
 }
 @Override
 public  void onDrawFrame(GL10gl){
 //TODOAuto-generatedmethodstub
 }

 }

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:

 package com.android.tutor;
 import android.app.Activity;
 import android.os.Bundle;
 public  class OpenGL_Lesson2 extends Activity{

 private OpenGlViewmOpenGlView;
 public  void onCreate(BundlesavedInstanceState){
 super .onCreate(savedInstanceState);

 mOpenGlView=new OpenGlView( this );
 setContentView(mOpenGlView);

 }
 }

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:

 package com.android.tutor;
 import android.content.Context;
 import android.opengl.GLSurfaceView;
 public  class OpenGlView extends GLSurfaceView{

 private OpenGlRendermOpenGlRender;
 public OpenGlView(Contextcontext){
 super (context);
 mOpenGlRender=new OpenGlRender();
 setRenderer(mOpenGlRender);
 }



 }

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:

 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(GL10gl,EGLConfigconfig){

 gl.glEnableClientState(GL10.GL_VERTEX_ARRAY);
 initTriangle();
 }
 @Override
 public  void onSurfaceChanged(GL10gl, int width, int height){

 gl.glViewport(0 , 0 ,width,height);
 }


 @Override
 public  void onDrawFrame(GL10gl){
 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(){
 //floathas4bytes
 ByteBuffervbb=ByteBuffer.allocateDirect(_nrOfVertices*3 * 4 );
 vbb.order(ByteOrder.nativeOrder());
 _vertexBuffer=vbb.asFloatBuffer();

 //shorthas4bytes
 ByteBufferibb=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 );
 }
 }

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~