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【Android开发学习17】Android OpenGL ES 光照与混合glDrawElements

 
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一、基础知识:


1..光照介绍:

环境光:
来自四面八方,所有场景中的对象都处于环境光的照射中。

漫射光:
由特定的光源产生,并在场景中的对象表面产生反射。
处于漫射光直接照射下的任何对象表面都变得很亮,而几乎未被照射到的区域就显示得要暗一些。


2.光照使用:
①设定光源参数:
//定义环境光(r,g,b,a)
FloatBuffer lightAmbient = FloatBuffer.wrap(new float[]{0.5f,0.5f,0.5f,1.0f});
//定义漫射光
FloatBuffer lightDiffuse = FloatBuffer.wrap(new float[]{1.0f,1.0f,1.0f,1.0f});

//定义光源的位置(前三个参数为坐标X,Y,Z; 第四个参数为1.0f,是告诉OpenGl这里指定的坐标就是光源的位置)
FloatBuffer lightPosition = FloatBuffer.wrap(new float[]{0.0f,0.0f,2.0f,1.0f});

②设置光源:
glLightfv (
int light,// 光源的ID
int pname, // 光源的类型
FloatBuffer params// 光源的数组
)
设定的属性,主要由第二个参数决定:
GL_AMBIENT环境光(光源泛光强度的RGBA值)
GL_DIFFUSE漫射光(光源漫反射强度的RGBA值)
GL_SPECULAR高光(光源镜面反射强度的RGBA值)
GL_POSITION位置(光源的位置)
GL_SPOT_DIRECTION方向(聚光灯的方向)
GL_SPOT_CUTOFF光的角度(聚光灯的截止角度)

//设置环境光
gl.glLightfv(GL10.GL_LIGHT1, GL10.GL_AMBIENT, lightAmbient);
//设置漫射光
gl.glLightfv(GL10.GL_LIGHT1, GL10.GL_DIFFUSE, lightDiffuse);
//设置光源的位置
gl.glLightfv(GL10.GL_LIGHT1, GL10.GL_POSITION, lightPosition);

③启用光源:
//启用一号光源
gl.glEnable(GL10.GL_LIGHT1);

3、混合实现:
如果开启混合,则根据Alpha值来显示透明效果;
如果未开启混合,则不会显示透明效果;

①在onSurfaceCreated方法中加入代码:
//设置光线,,1.0f为全光线,a=50%
gl.glColor4f(1.0f,1.0f,1.0f,0.5f);
// 基于源象素alpha通道值的半透明混合函数
gl.glBlendFunc(GL10.GL_SRC_ALPHA,GL10.GL_ONE);

其中,glColor4f以全亮度绘制此物体,并对其进行50%的alpha混合(半透明)。
当混合选项打开时,此物体将会产生50%的透明效果,
alpha通道的值为0.0意味着物体材质是完全透明的,
为1.0则意味着完全不透明。

②打开混合开关:
gl.glEnable(GL10.GL_BLEND);// 打开混合

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"
    />
</LinearLayout>


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

package com.yarin.android.Examples_12_07;

import android.app.Activity;
import android.content.res.Resources;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.opengl.GLSurfaceView;
import android.os.Bundle;
import android.view.KeyEvent;

public class Activity01 extends Activity
{
	GLRender render = new GLRender();
	
	/** Called when the activity is first created. */
	@Override
	public void onCreate(Bundle savedInstanceState)
	{
		super.onCreate(savedInstanceState);
		GLImage.load(this.getResources());
		GLSurfaceView glView = new GLSurfaceView(this);
		
		glView.setRenderer(render);
		setContentView(glView);
	}
}


class GLImage
{
	public static Bitmap mBitmap;
	public static void load(Resources resources)
	{
		mBitmap = BitmapFactory.decodeResource(resources, R.drawable.img);
	}
}


\src\com\yarin\android\Examples\GLRender.java

package com.yarin.android.Examples_12_07;

import java.nio.ByteBuffer;
import java.nio.FloatBuffer;
import java.nio.IntBuffer;

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

import android.opengl.GLUtils;
import android.opengl.GLSurfaceView.Renderer;
import android.view.KeyEvent;

public class GLRender implements Renderer
{
	boolean key = true;
	float xrot, yrot;
	float xspeed, yspeed;
	float z = -5.0f;
	int one = 0x10000;
	
	//光线参数
	FloatBuffer lightAmbient = FloatBuffer.wrap(new float[]{0.5f,0.5f,0.5f,1.0f}); 
	FloatBuffer lightDiffuse = FloatBuffer.wrap(new float[]{1.0f,1.0f,1.0f,1.0f}); 
	FloatBuffer lightPosition = FloatBuffer.wrap(new float[]{0.0f,0.0f,2.0f,1.0f}); 
	
	int filter = 1;
	
	int [] texture;
	
	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 normals = IntBuffer.wrap(new int[]{
			0,0,one,
			0,0,one,
			0,0,one,
			0,0,one,
			
			0,0,one,
			0,0,one,
			0,0,one,
			0,0,one,
			
			0,one,0,
			0,one,0,
			0,one,0,
			0,one,0,
			
			0,-one,0,
			0,-one,0,
			0,-one,0,
			0,-one,0,
			
			one,0,0,
			one,0,0,
			one,0,0,
			one,0,0,
			
			-one,0,0,
			-one,0,0,
			-one,0,0,
			-one,0,0,
	});
	
	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,
	});
	
	@Override
	public void onDrawFrame(GL10 gl)
	{
		// 清除屏幕和深度缓存
		gl.glClear(GL10.GL_COLOR_BUFFER_BIT | GL10.GL_DEPTH_BUFFER_BIT);
		
		gl.glMatrixMode(GL10.GL_MODELVIEW);
		// 重置当前的模型观察矩阵
		gl.glLoadIdentity();
		
		gl.glEnable(GL10.GL_LIGHTING);
		
		////////////////
		gl.glTranslatef(0.0f, 0.0f, z);
		
		//设置旋转
		gl.glRotatef(xrot, 1.0f, 0.0f, 0.0f);
		gl.glRotatef(yrot, 0.0f, 1.0f, 0.0f);

		//设置纹理
		gl.glBindTexture(GL10.GL_TEXTURE_2D, texture[filter]);
		
		gl.glNormalPointer(GL10.GL_FIXED, 0, normals);
		gl.glVertexPointer(3, GL10.GL_FIXED, 0, vertices);
		gl.glTexCoordPointer(2, GL10.GL_FIXED, 0, texCoords);

		gl.glEnableClientState(GL10.GL_NORMAL_ARRAY);
		gl.glEnableClientState(GL10.GL_VERTEX_ARRAY);
		gl.glEnableClientState(GL10.GL_TEXTURE_COORD_ARRAY);
		
		
		//绘制四边形
		gl.glDrawElements(GL10.GL_TRIANGLE_STRIP, 24,  GL10.GL_UNSIGNED_BYTE, indices);
		
	    gl.glDisableClientState(GL10.GL_TEXTURE_COORD_ARRAY);
	    gl.glDisableClientState(GL10.GL_VERTEX_ARRAY);
	    gl.glDisableClientState(GL10.GL_NORMAL_ARRAY);
	    //修改旋转角度
	    xrot+=0.3f; 
	    yrot+=0.2f;
	    
	    //gl.glDisable(GL10.GL_BLEND);		// 关闭混合
	    //gl.glEnable(GL10.GL_DEPTH_TEST);	// 打开深度测试
	    ///*
	    //混合开关
	    if (key)
		{
	    	gl.glEnable(GL10.GL_BLEND);			// 打开混合
	    	gl.glDisable(GL10.GL_DEPTH_TEST);	// 关闭深度测试
		}
	    else 
	    {
	    	gl.glDisable(GL10.GL_BLEND);		// 关闭混合
	    	gl.glEnable(GL10.GL_DEPTH_TEST);	// 打开深度测试
		}
		//*/
	}

	@Override
	public void onSurfaceChanged(GL10 gl, int width, int height)
	{
		float ratio = (float) width / height;
		//设置OpenGL场景的大小
		gl.glViewport(0, 0, width, height);
		//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)
	{
		gl.glDisable(GL10.GL_DITHER);

		// 告诉系统对透视进行修正
		gl.glHint(GL10.GL_PERSPECTIVE_CORRECTION_HINT, GL10.GL_FASTEST);
		// 黑色背景
		gl.glClearColor(0, 0, 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);
		
		//设置光线,,1.0f为全光线,a=50%
		gl.glColor4f(1.0f,1.0f,1.0f,0.5f);	

		// 基于源象素alpha通道值的半透明混合函数
		gl.glBlendFunc(GL10.GL_SRC_ALPHA,GL10.GL_ONE);		

		//纹理相关
		IntBuffer textureBuffer = IntBuffer.allocate(3);
		gl.glGenTextures(3, textureBuffer);
		texture = textureBuffer.array();
		
		gl.glBindTexture(GL10.GL_TEXTURE_2D, texture[0]);
		gl.glTexParameterx(GL10.GL_TEXTURE_2D,GL10.GL_TEXTURE_MAG_FILTER,GL10.GL_NEAREST); // ( NEW )
		gl.glTexParameterx(GL10.GL_TEXTURE_2D,GL10.GL_TEXTURE_MIN_FILTER,GL10.GL_NEAREST); // ( NEW )
		GLUtils.texImage2D(GL10.GL_TEXTURE_2D, 0, GLImage.mBitmap, 0);
		
		gl.glBindTexture(GL10.GL_TEXTURE_2D, texture[1]);
		gl.glTexParameterx(GL10.GL_TEXTURE_2D,GL10.GL_TEXTURE_MAG_FILTER,GL10.GL_LINEAR); // ( NEW )
		gl.glTexParameterx(GL10.GL_TEXTURE_2D,GL10.GL_TEXTURE_MIN_FILTER,GL10.GL_LINEAR); // ( NEW )
		GLUtils.texImage2D(GL10.GL_TEXTURE_2D, 0, GLImage.mBitmap, 0);
		
		gl.glBindTexture(GL10.GL_TEXTURE_2D, texture[2]);
		gl.glTexParameterx(GL10.GL_TEXTURE_2D,GL10.GL_TEXTURE_MAG_FILTER,GL10.GL_LINEAR); // ( NEW )
		gl.glTexParameterx(GL10.GL_TEXTURE_2D,GL10.GL_TEXTURE_MIN_FILTER,GL10.GL_LINEAR); // ( NEW )
		GLUtils.texImage2D(GL10.GL_TEXTURE_2D, 0, GLImage.mBitmap, 0);
		
		//深度测试相关
		gl.glClearDepthf(1.0f);
		gl.glDepthFunc(GL10.GL_LEQUAL);
		gl.glHint(GL10.GL_PERSPECTIVE_CORRECTION_HINT, GL10.GL_NICEST);
		gl.glEnable(GL10.GL_TEXTURE_2D);
		
		//设置环境光
	    gl.glLightfv(GL10.GL_LIGHT1, GL10.GL_AMBIENT, lightAmbient);

	    //设置漫射光
	    gl.glLightfv(GL10.GL_LIGHT1, GL10.GL_DIFFUSE, lightDiffuse);

	    //设置光源位置
	    gl.glLightfv(GL10.GL_LIGHT1, GL10.GL_POSITION, lightPosition);
	    
	    //开启一号光源
	    gl.glEnable(GL10.GL_LIGHT1);
	    
	    //开启混合
	    gl.glEnable(GL10.GL_BLEND);
	    
	    key=true;
	}
}


三、效果:

四、思考:

将四方体的每个面贴不同的图片,实现效果如下:

本文博客源地址:http://blog.csdn.net/ypist

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