Android 中使用OpenGL ES进行2D开发（绘制矩形）

必须要先回顾下这张图，我们可以定义6个点，每3个点组成一个三角形，两个三角形组成一个矩形，但是搞计算机的总是懒或者说不喜欢重复的东西，我们也可以定义4个点，如右边的图案，V1，V2，V3组成一个三角形，然后V1，V3，V4组成另外一个三角形。

因为定义了4个点，所以我们需要更多的空间来储存来存储点了。下面是跟三角形代码不同的地方，用红色标出了。

ByteBuffer byteBuffer = ByteBuffer.allocateDirect(4 * 2 * 4);

vertices.put( new float[] {  -80f,   -120f,

                                         80f,  -120f,

                                         -80f, 120f,

                                         80f,120f});

ByteBuffer indicesBuffer = ByteBuffer.allocateDirect(6 * 2);

indices.put(new short[] { 0, 1, 2,1,2,3});

gl.glDrawElements(GL10.GL_TRIANGLE_STRIP, 6, GL10.GL_UNSIGNED_SHORT, indices);

还是上矩形代码吧，示例比较重要

package com.waitingfy.android.glbasics;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.app.Activity;import android.opengl.GLSurfaceView;import android.opengl.GLSurfaceView.Renderer;import android.os.Bundle;import android.util.Log;import android.view.Window;import android.view.WindowManager;public class FirstRectangleTest extends Activity {public GLSurfaceView glView;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);// 去掉activity的标题，全屏显示requestWindowFeature(Window.FEATURE_NO_TITLE);getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,WindowManager.LayoutParams.FLAG_FULLSCREEN);glView = new GLSurfaceView(this);glView.setRenderer(new SimpleRenderer());setContentView(glView);}@Overridepublic void onResume() {super.onPause();glView.onResume();}@Overridepublic void onPause() {super.onPause();glView.onPause();}class SimpleRenderer implements Renderer {FloatBuffer vertices;ShortBuffer indices;public SimpleRenderer() {ByteBuffer byteBuffer = ByteBuffer.allocateDirect(4 * 2 * 4);byteBuffer.order(ByteOrder.nativeOrder());vertices = byteBuffer.asFloatBuffer();//定义四个点vertices.put( new float[] {  -80f,-120f,                                          80f,-120f,                                         -80f,120f,                                          80f,120f});ByteBuffer indicesBuffer = ByteBuffer.allocateDirect(6 * 2);indicesBuffer.order(ByteOrder.nativeOrder());indices = indicesBuffer.asShortBuffer();indices.put(new short[] { 0, 1, 2, 1, 2, 3 });//indices.flip() == indices.position(0)indices.flip();vertices.flip();}@Overridepublic void onSurfaceCreated(GL10 gl, EGLConfig config) {Log.d("GLSurfaceViewTest", "surface created");}@Overridepublic void onSurfaceChanged(GL10 gl, int width, int height) {Log.d("GLSurfaceViewTest", "surface changed: " + width + "x"+ height);}@Overridepublic void onDrawFrame(GL10 gl) {//定义显示在屏幕上的什么位置(opengl 自动转换)gl.glViewport(0, 0, glView.getWidth(), glView.getHeight());// gl.glViewport(50, 50,430, 550);gl.glClear(GL10.GL_COLOR_BUFFER_BIT);gl.glMatrixMode(GL10.GL_PROJECTION);gl.glLoadIdentity();//设置视锥体的大小，一个很扁的长方体gl.glOrthof(-160, 160, -240, 240, 1, -1);//颜色设置为红色gl.glColor4f(1, 0, 0, 1);gl.glEnableClientState(GL10.GL_VERTEX_ARRAY);gl.glVertexPointer( 2, GL10.GL_FLOAT, 0, vertices);                gl.glDrawElements(GL10.GL_TRIANGLE_STRIP, 6, GL10.GL_UNSIGNED_SHORT, indices);}}}

效果图和虚拟3D中的样子：

 

原文链接： http://www.waitingfy.com/?p=61

源码下载 gl-basics