【Android开发学习14】Android OpenGL ES 纹理映射之glDrawElements

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目标: 为四方体的每个面贴上一张图片，并自动旋转。

一、基础知识:
要实现每个面上贴一张图片，首先需要创建一个纹理，并使用图片来生成一个纹理。
==========================================================================

1.初始化:

IntBuffer intBuffer = IntBuffer.allocate(2);
// 1.允许2D贴图,纹理
gl.glEnable(GL10.GL_TEXTURE_2D);
// 2.创建纹理
gl.glGenTextures(2, intBuffer);
texture = intBuffer.get(0);
// 3.设置要使用的纹理
gl.glBindTexture(GL10.GL_TEXTURE_2D, texture);
// 4.生成纹理
GLUtils.texImage2D(GL10.GL_TEXTURE_2D, 0, GLImage.close_Bitmap, 0);
// 5.线形滤波
gl.glTexParameterx(GL10.GL_TEXTURE_2D, GL10.GL_TEXTURE_MIN_FILTER, GL10.GL_LINEAR);
gl.glTexParameterx(GL10.GL_TEXTURE_2D, GL10.GL_TEXTURE_MAG_FILTER, GL10.GL_LINEAR);

==========================================================================

2.使用:

// 1.清除屏幕和深度缓存
gl.glClear(GL10.GL_COLOR_BUFFER_BIT | GL10.GL_DEPTH_BUFFER_BIT);

// 2.重置当前的模型观察矩阵
gl.glLoadIdentity();
// 3.移动到指定的位置
gl.glTranslatef(0.0f, 0.0f, -5.0f);

// 4.设置3个方向的旋转
gl.glRotatef(xrot, 1.0f, 0.0f, 0.0f);
gl.glRotatef(yrot, 0.0f, 1.0f, 0.0f);
gl.glRotatef(zrot, 0.0f, 0.0f, 1.0f);

texture = intBuffer.get(1);;
// 5.绑定纹理
gl.glBindTexture(GL10.GL_TEXTURE_2D, texture);

// 6.开启顶点和纹理功能
gl.glEnableClientState(GL10.GL_VERTEX_ARRAY);
gl.glEnableClientState(GL10.GL_TEXTURE_COORD_ARRAY);

// 7.纹理和四边形对应的顶点
gl.glVertexPointer(3, GL10.GL_FIXED, 0, vertices);
gl.glTexCoordPointer(2, GL10.GL_FIXED, 0, texCoords);

// 8.绘制0
GLUtils.texImage2D(GL10.GL_TEXTURE_2D, 0, GLImage.iBitmap, 0);
gl.glDrawElements(GL10.GL_TRIANGLE_STRIP, 4, GL10.GL_UNSIGNED_BYTE, indices_0);

// 9.关闭顶点和纹理功能
gl.glDisableClientState(GL10.GL_TEXTURE_COORD_ARRAY);
gl.glDisableClientState(GL10.GL_VERTEX_ARRAY);
==========================================================================

二、实现:

1. 界面编辑：
【res\layout\main.xml】

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    >
<TextView  
    android:layout_width="fill_parent" 
    android:layout_height="wrap_content" 
    android:text="@string/hello"
    />

<Button
    android:id="@+id/button1"
    android:layout_width="145dp"
    android:layout_height="wrap_content"
    android:text="演示开始" />

</LinearLayout>

2.代码编辑:
【\src\com\yarin\android\Examples\Activity01.java】

package com.yarin.android.Examples_12_05;

import java.io.IOException;
import java.io.InputStream;

import javax.microedition.khronos.opengles.GL10;

import android.app.Activity;
import android.content.res.Resources;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.opengl.GLSurfaceView;
import android.opengl.GLUtils;
import android.opengl.GLSurfaceView.Renderer;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;

public class Activity01 extends Activity
{
	Renderer render = new GLRender();
	GLSurfaceView glView;
	Button start;			// 演示开始

	
	/** Called when the activity is first created. */
	@Override
	public void onCreate(Bundle savedInstanceState)
	{
		super.onCreate(savedInstanceState);
		GLImage.load(this.getResources());
		glView = new GLSurfaceView(this);
		
		
		glView.setRenderer(render);
		setContentView(R.layout.main);
		start=(Button)findViewById(R.id.button1);	// "演示开始"按钮初始化
		start.setOnClickListener(new View.OnClickListener() {
			
			@Override
			public void onClick(View v) {
				// TODO Auto-generated method stub
				setContentView(glView);
			}
		});
		//setContentView(glView);
	}
}


class GLImage
{
	public static Bitmap iBitmap;
	public static Bitmap jBitmap;
	public static Bitmap kBitmap;
	public static Bitmap lBitmap;
	public static Bitmap mBitmap;
	public static Bitmap nBitmap;
	public static Bitmap close_Bitmap;
	
	
	public static void load(Resources resources)
	{
		iBitmap = BitmapFactory.decodeResource(resources, R.drawable.img);
		jBitmap = BitmapFactory.decodeResource(resources, R.drawable.jmg);
		kBitmap = BitmapFactory.decodeResource(resources, R.drawable.kmg);
		lBitmap = BitmapFactory.decodeResource(resources, R.drawable.lmg);
		mBitmap = BitmapFactory.decodeResource(resources, R.drawable.mmg);
		nBitmap = BitmapFactory.decodeResource(resources, R.drawable.nmg);
		close_Bitmap = BitmapFactory.decodeResource(resources, R.drawable.close);
	}
}

【\src\com\yarin\android\Examples\GLRender.java】
package com.yarin.android.Examples_12_05;

import java.io.IOException;
import java.io.InputStream;
import java.nio.ByteBuffer;
import java.nio.IntBuffer;

import javax.microedition.khronos.egl.EGLConfig;
import javax.microedition.khronos.opengles.GL10;

import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.opengl.GLUtils;
import android.opengl.GLSurfaceView.Renderer;

public class GLRender implements Renderer
{
	float xrot, yrot, zrot;
	int texture = -1;
	int one = 0x10000;
	
	IntBuffer intBuffer = IntBuffer.allocate(2);
	int n_view_start_x=100;
	int n_view_start_y=20;
	int n_close_flag=0;	// 1: close_icon show. 0: close_icon hide.
	public int textureId;
	
	IntBuffer vertices = IntBuffer.wrap(new int[]{
			-one,-one,one,
			one,-one,one,
			one,one,one,
			-one,one,one,
			
			-one,-one,-one,
			-one,one,-one,
			one,one,-one,
			one,-one,-one,
			
			-one,one,-one,
			-one,one,one,
			one,one,one,
			one,one,-one,
			
			-one,-one,-one,
			one,-one,-one,
			one,-one,one,
			-one,-one,one,
			
			one,-one,-one,
			one,one,-one,
			one,one,one,
			one,-one,one,
			
			-one,-one,-one,
			-one,-one,one,
			-one,one,one,
			-one,one,-one,
			
	});
	IntBuffer texCoords = IntBuffer.wrap(new int[]{
		one,0,0,0,0,one,one,one,	
		0,0,0,one,one,one,one,0,
		one,one,one,0,0,0,0,one,
		0,one,one,one,one,0,0,0,
		0,0,0,one,one,one,one,0,
		one,0,0,0,0,one,one,one,
	});
	
	ByteBuffer indices = ByteBuffer.wrap(new byte[]{
			0,1,3,2,
			4,5,7,6,
			8,9,11,10,
			12,13,15,14,
			16,17,19,18,
			20,21,23,22,
	});
	
	ByteBuffer indices_0 = ByteBuffer.wrap(new byte[]{
			0,1,3,2
	});

	ByteBuffer indices_1 = ByteBuffer.wrap(new byte[]{
			4,5,7,6
	});
	
	ByteBuffer indices_2 = ByteBuffer.wrap(new byte[]{
			8,9,11,10
	});
	
	ByteBuffer indices_3 = ByteBuffer.wrap(new byte[]{
			12,13,15,14
	});
	
	ByteBuffer indices_4 = ByteBuffer.wrap(new byte[]{
			16,17,19,18
	});
	
	ByteBuffer indices_5 = ByteBuffer.wrap(new byte[]{
			20,21,23,22
	});
	
    //正方形的4个顶点   
    private IntBuffer quaterBuffer = IntBuffer.wrap(new int[]{  
               one,one,0,  
               -one,one,0,  
               one,-one,0,  
               -one,-one,0});  
    IntBuffer texCoords_rect = IntBuffer.wrap(new int[]{
            0,1,1,1,1,0,0,0,               
          });

	@Override
	public void onDrawFrame(GL10 gl)
	{
		// 1.清除屏幕和深度缓存
		gl.glClear(GL10.GL_COLOR_BUFFER_BIT | GL10.GL_DEPTH_BUFFER_BIT);

		// 2.重置当前的模型观察矩阵
		gl.glLoadIdentity();
		// 3.移动到指定的位置
		gl.glTranslatef(0.0f, 0.0f, -5.0f);

		// 4.设置3个方向的旋转
		gl.glRotatef(xrot, 1.0f, 0.0f, 0.0f);
		gl.glRotatef(yrot, 0.0f, 1.0f, 0.0f);
		gl.glRotatef(zrot, 0.0f, 0.0f, 1.0f);

		texture = intBuffer.get(1);;
		//  5.绑定纹理
		gl.glBindTexture(GL10.GL_TEXTURE_2D, texture);
		
		// 6.开启顶点和纹理功能
		gl.glEnableClientState(GL10.GL_VERTEX_ARRAY);
		gl.glEnableClientState(GL10.GL_TEXTURE_COORD_ARRAY);
		
		// 7.纹理和四边形对应的顶点
		gl.glVertexPointer(3, GL10.GL_FIXED, 0, vertices);
		gl.glTexCoordPointer(2, GL10.GL_FIXED, 0, texCoords);

		// 8.绘制0
		GLUtils.texImage2D(GL10.GL_TEXTURE_2D, 0, GLImage.iBitmap, 0);
		gl.glDrawElements(GL10.GL_TRIANGLE_STRIP, 4,  GL10.GL_UNSIGNED_BYTE, indices_0);

		//绘制1
		GLUtils.texImage2D(GL10.GL_TEXTURE_2D, 0, GLImage.jBitmap, 0);
		gl.glDrawElements(GL10.GL_TRIANGLE_STRIP, 4,  GL10.GL_UNSIGNED_BYTE, indices_1);

		//绘制2
		GLUtils.texImage2D(GL10.GL_TEXTURE_2D, 0, GLImage.kBitmap, 0);
		gl.glDrawElements(GL10.GL_TRIANGLE_STRIP, 4,  GL10.GL_UNSIGNED_BYTE, indices_2);
		
		//绘制3
		GLUtils.texImage2D(GL10.GL_TEXTURE_2D, 0, GLImage.lBitmap, 0);
		gl.glDrawElements(GL10.GL_TRIANGLE_STRIP, 4,  GL10.GL_UNSIGNED_BYTE, indices_3);
		
		//绘制4
		GLUtils.texImage2D(GL10.GL_TEXTURE_2D, 0, GLImage.mBitmap, 0);
		gl.glDrawElements(GL10.GL_TRIANGLE_STRIP, 4,  GL10.GL_UNSIGNED_BYTE, indices_4);
		
		//绘制5
		GLUtils.texImage2D(GL10.GL_TEXTURE_2D, 0, GLImage.close_Bitmap, 0);
		gl.glDrawElements(GL10.GL_TRIANGLE_STRIP, 4,  GL10.GL_UNSIGNED_BYTE, indices_5);
			
		if(0==n_close_flag)
		{
		    
		    // 重置当前的模型观察矩阵   
	        gl.glLoadIdentity();  
	        // 左移 1.5 单位，并移入屏幕 5.0   
	        gl.glTranslatef(-4.5f, 3.0f, -5.0f);  
	        
			gl.glEnableClientState(GL10.GL_VERTEX_ARRAY);
			gl.glEnableClientState(GL10.GL_TEXTURE_COORD_ARRAY);
			
	        texture = intBuffer.get(0);
			// 绑定纹理
			gl.glBindTexture(GL10.GL_TEXTURE_2D, texture);
			GLUtils.texImage2D(GL10.GL_TEXTURE_2D, 0, GLImage.close_Bitmap, 0);
			
			// 绘制关闭按钮
	        // 设置和绘制正方形   
	        gl.glVertexPointer(3, GL10.GL_FIXED, 0, quaterBuffer);  
	        gl.glTexCoordPointer(2, GL10.GL_FIXED, 0, texCoords_rect);

	        gl.glDrawArrays(GL10.GL_TRIANGLE_STRIP, 0, 4);
	        //gl.glDrawElements(GL10.GL_TRIANGLE_STRIP, 4,  GL10.GL_UNSIGNED_BYTE, indices_5);
	        
			n_close_flag=1;
		}

        // 9.关闭顶点和纹理功能
	    gl.glDisableClientState(GL10.GL_TEXTURE_COORD_ARRAY);
	    gl.glDisableClientState(GL10.GL_VERTEX_ARRAY);
	    
	    xrot+=0.5f;
	    yrot+=0.6f; 
	    zrot+=0.3f; 
		
	}

	@Override
	public void onSurfaceChanged(GL10 gl, int width, int height)
	{
		float ratio = (float) (width-n_view_start_x) / (height-n_view_start_x);
		//设置OpenGL场景的大小
		//gl.glViewport(0, 0, width, height);
		gl.glViewport(n_view_start_x, n_view_start_y, width-n_view_start_x, height-n_view_start_y);
		
		//设置投影矩阵
		gl.glMatrixMode(GL10.GL_PROJECTION);
		//重置投影矩阵
		gl.glLoadIdentity();
		// 设置视口的大小
		gl.glFrustumf(-ratio, ratio, -1, 1, 1, 10);
		// 选择模型观察矩阵
		gl.glMatrixMode(GL10.GL_MODELVIEW);	
		// 重置模型观察矩阵
		gl.glLoadIdentity();	
		
	}

	@Override
	public void onSurfaceCreated(GL10 gl, EGLConfig config)
	{
		// 绿色背景
		gl.glClearColor(0, 1, 0, 0);
		
		gl.glEnable(GL10.GL_CULL_FACE);
		// 启用阴影平滑
		gl.glShadeModel(GL10.GL_SMOOTH);
		// 启用深度测试
		gl.glEnable(GL10.GL_DEPTH_TEST);
		
		//启用纹理映射
		gl.glClearDepthf(1.0f);
		//深度测试的类型
		gl.glDepthFunc(GL10.GL_LEQUAL);
		//精细的透视修正
		gl.glHint(GL10.GL_PERSPECTIVE_CORRECTION_HINT, GL10.GL_NICEST);
		
/*		
		// 1.允许2D贴图,纹理
		gl.glEnable(GL10.GL_TEXTURE_2D);
		
		IntBuffer intBuffer = IntBuffer.allocate(1);
		// 2.创建纹理
		gl.glGenTextures(1, intBuffer);
		texture = intBuffer.get();
		// 3.设置要使用的纹理
		gl.glBindTexture(GL10.GL_TEXTURE_2D, texture);
		
		// 4.生成纹理
		GLUtils.texImage2D(GL10.GL_TEXTURE_2D, 0, GLImage.mBitmap, 0);
		
		// 5.线形滤波
		gl.glTexParameterx(GL10.GL_TEXTURE_2D, GL10.GL_TEXTURE_MIN_FILTER, GL10.GL_LINEAR);
		gl.glTexParameterx(GL10.GL_TEXTURE_2D, GL10.GL_TEXTURE_MAG_FILTER, GL10.GL_LINEAR);
*/

		// 1.允许2D贴图,纹理
		gl.glEnable(GL10.GL_TEXTURE_2D);
		
		// 2.创建纹理
		gl.glGenTextures(2, intBuffer);
		
		texture = intBuffer.get(0);
		// 3.设置要使用的纹理
		gl.glBindTexture(GL10.GL_TEXTURE_2D, texture);
		// 4.生成纹理
		GLUtils.texImage2D(GL10.GL_TEXTURE_2D, 0, GLImage.close_Bitmap, 0);

		texture = intBuffer.get(1);
		// 3.设置要使用的纹理
		gl.glBindTexture(GL10.GL_TEXTURE_2D, texture);
		// 4.生成纹理
		GLUtils.texImage2D(GL10.GL_TEXTURE_2D, 0, GLImage.nBitmap, 0);
		
		// 5.线形滤波
		gl.glTexParameterx(GL10.GL_TEXTURE_2D, GL10.GL_TEXTURE_MIN_FILTER, GL10.GL_LINEAR);
		gl.glTexParameterx(GL10.GL_TEXTURE_2D, GL10.GL_TEXTURE_MAG_FILTER, GL10.GL_LINEAR);

	}

}

扩展阅读: 连接一

【练习】使用gldrawarrays函数实现本次四方体的旋转效果。

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