Android OpenGL20 模型，视图，投影与Viewport <7>

对于很多初学者,视图投影之类非常的难理解,然而这个东西非常非常的重要,如果不是非常清楚,根本无法定位3D Object(空间坐标)和观察角度(观察角度不一样,效果就不一样),自己阅博无数,发现了一篇非常棒的blog文章:

/article/1389116.html

由于尽量保证自己博客的原创性,所以不方便装载,所以reviewer一定要看上面链接的文章,图文并茂,然后通过自己的测试程序进行测试,就会彻底明白.当然这个博主是苹果APP的,但是没有关系,理论是通用的.

这里大致总结一下:

概念一:

a> : viewport（视口）变换 : 结合程序,下面是定义点的坐标,平时看sample比较多就会发现,x,y,z轴都用标量为1去设置

private float vertexs[]={
0.0f,0.0f,0.0f,
1.0f,0.0f,0.0f,
0.0f,1.0f,0.0f
};

但是显示在移动设备屏幕上是一个3D图像,但是这个1是如何转换到屏幕的呢?这个1即不代表像素,又没有代表一个比例(比如1:500,1代表占用500像素),却在程序运行后显示一个3D图形.这个地方就是上面博客中提到的:从 Normalized Device Space 到 Window Space 就是 viewport 变换过程:



看看上面的,程序中设置就是Normalized Device Space上的"坐标",如果要显示在移动设备的屏幕上,就需要一个转换,转换规则



其中上面转换公式中的参数,x,y,width,height是通过:

glViewport(x, y, width, height);

设置的;

(xw, yw)是屏幕坐标;

(xnd, ynd)是投影之后经归一化之后的点（上图中 Normalized Device Space 空间的点）;

概念二 :

b> : 模型视图变换 : 这里分两种,

1> : 变换3D Object在空间中的位置和旋转,而观察者(很多地方表述为:Camera)的位置保持不变;

2> : 保持3D Object在空间中的位置和旋转不变,观察者的位置变化.

所以当需要观察3D Object的不同角度的时候,可以通过变换3D Object的位置或角度,也可以变换观察者的位置或角度.

如果变化3D Object可以通过矩阵平移,旋转,缩放等操作;

如果变化观察者角度 :

gluLookAt(eyex, eyey, eyez, centerx, centery, centerz, upx, upy, upz);

eye 表示 camera/viewer 的位置， center 表示相机或眼睛的焦点（它与 eye 共同来决定 eye 的朝向），而 up 表示 eye 的正上方向，注意 up 只表示方向，与大小无关。通过调用此函数，就能够设定观察的场景，在这个场景中的物体就会被 OpenGL 处理。在 OpenGL 中，eye 的默认位置是在原点，指向 Z 轴的负方向（屏幕往里），up 方向为 Y 轴的正方向.

概念三 :

c> : 投影变换 : 投影变换的目的是确定 3D 空间的物体如何投影到 2D 平面上，从而形成2D图像，这些 2D 图像再经视口变换就被渲染到屏幕上;

这个也包含两种情况:

1> : 正交投影;

2> : 透视投影;

1> : 正交投影:可以把正交投影看成是透视投影的特殊形式：即近裁剪面与远裁剪面除了Z 位置外完全相同，因此物体始终保持一致的大小，即便是在远处看上去也不会变小.



这个图其实非常好了,但是觉得还差一样东西,就可以更明白了,3D Object物体,这个物体一般如果想被观察者看到,就需要将3D物体放在上面的那个立体盒子中(当然很多情况通过设置了near,far会将3D物体"放在盒子外面了"),也就是说,要想看到3D物理,首先需要将其置于两个切面之间(即图中黑色斜线面和蓝绿色斜线面之间),同时如果有必要还需要将3D物理进行缩放操作(这样方便从黑色斜面观察进去).

设置正交投影:

glOrtho(left, right, bottom, top, zNear, zFar);

left，right， bootom，top 定义了 near 裁剪面大小，而 zNear 和 zFar 定义了从 Camera/Viewer 到远近两个裁剪面的距离（注意这两个距离都是正值）.

2> : 透视投影:这个地方由于使用的库不一样,存在两种:

<I> : OpenGL es提供的模型:

glFrustum(left, right, bottom, top, zNear, zFar);

left，right， bootom，top 定义了 near 裁剪面大小，而 zNear 和 zFar 定义了从 Camera/Viewer 到远近两个裁剪面的距离（注意这两个距离都是正值）。由这六个参数可以定义出六个裁剪面构成的锥体，这个锥体通常被称之为视锥体或视景体。只有在这个锥体内的物体才是可以见的，不在这个锥体内的物体就相当于不再视线范围内，因而会被裁减掉，OpenGL
不会这些物体进行渲染

通过glFrustum机型设置该模型!

<II> : glut辅助库模型如下:



注意这个模型和上面模型的标注部分,样子是一样的,但是标注是不一样的.

gluPerspective(fovy, aspect, zNear, zFar);

fovy 定义了 camera 在 y 方向上的视线角度（介于 0 ~ 180 之间），aspect 定义了近裁剪面的宽高比 aspect = w/h，而 zNear 和 zFar 定义了从 Camera/Viewer 到远近两个裁剪面的距离（注意这两个距离都是正值）。这四个参数同样也定义了一个视锥体。

在 OpenGL ES 2.0 中，我们也需要自己实现该函数。我们可以通过三角公式 tan(fovy/2) = (h / 2)/zNear 计算出 h ，然后再根据 w = h * aspect 计算出 w，这样就可以得到 left, right, top, bottom, zNear, zFar 六个参数，代入在介绍视锥体时提到的公式即可.

补充两个图:





结论:

注意

写 OpenGL 代码时从前到后的顺序依次是：设定 viewport（视口变换），设定投影变换，设定视图变换，设定模型变换，在本地坐标空间描绘物体。而在前面为了便于理解做介绍时，说的顺序是OpenGL 中物体最初是在本地坐标空间中，然后转换到世界坐标空间，再到 camera 视图空间，再到投影空间。由于模型变换包括了本地空间变换到世界坐标空间，所以我们理解3D 变换是一个顺序，而真正写代码时则是以相反的顺序进行的，如果从左乘矩阵这点上去理解就很容易明白为什么会是反序的

重点中的重点,如何将上面的模型转换到程序中,在程序中如何体现:

我们一般会定义:

private float[] mMVPMatrix = new float[16];
private float[] mViewMatrix = new float[16];
private float[] mProjectionMatrix = new float[16];

<1> : mViewMatrix是保存4*4的矩阵信息,这个是观察者的眼睛的位置(或者叫做Camera):

Matrix.setLookAtM(mViewMatrix, 0, eyeX, eyeY, eyeZ, lookX, lookY, lookZ, upX, upY, upZ);

这个方法在前面介绍了用途,这里将会将设置的矩阵信息保存到mViewMatrix矩阵里面返回,这样我就可以获取眼睛在空间中的基位置,即后面要调整Camera,位置就需要乘以这个基位置矩阵,从而获得最终的Camera位置.

<2> : mProjectionMatrix是保存透视矩阵信息的:我们通过下面建立一个透视模型,然后将这个模型保存到这个矩阵中,算是基矩阵.

Matrix.frustumM(mProjectionMatrix, 0, left, right, bottom, top, near, far);

设置透视后,保存信息通过mProjectionMatrix返回.

<3> : mMVPMatrix是保存上面两个建立起来的模型,这个模型即观察者,观察范围和角度都一定设定了的模型,这个模型矩阵的表示是通过观察者和透视矩阵两个相乘得到的:

Matrix.setIdentityM(mModelMatrix, 0);
Matrix.translateM(mModelMatrix, 0, 0.0f, 0.0f, -5.0f);

Matrix.multiplyMM(mMVPMatrix, 0, mViewMatrix, 0, mModelMatrix, 0);
Matrix.multiplyMM(mMVPMatrix, 0, mProjectionMatrix, 0, mMVPMatrix, 0);

后面的绘制坐标,比如绘制三角形,给出三角形的坐标,但是在程序里面给出的都是"绝对坐标",或者是"理论坐标",将这些坐标*mMVPMatrix矩阵,才能够将这个三角形映射到观察模型中,从而显示在观察模型(透视模型)中,其中上面mModelMatrix是物理(即如三角形)初始定位点,即三角形的坐标会依据这个进行.

所以通过上面三步,就建立起透视观测模型,后面的物理坐标设置乘以mMVPMatrix矩阵,就可以让物理定位到模型中显示(当然这个是给出了显示的依据,实际物理不一定会显示在这个透视模型中,可能在之外,所以说这一种参考依据)

根据这个可以做一个Android Demo测试一下Android studio工程[]:

代码片区如下:

package org.pumpkin.pumpkintutor2gsls;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;

import org.pumpkin.pumpkintutor2gsls.tutor2.cube.CubeSurfaceView;
import org.pumpkin.pumpkintutor2gsls.tutor2.triangle.TriangleSurfaceView;
import org.pumpkin.pumpkintutor2gsls.tutor2.triangle1.TriangleSurfaceView1;

public class PumpKinMainActivity extends AppCompatActivity {

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(new TriangleSurfaceView1(this)/*new CubeSurfaceView(this)*//*new TriangleSurfaceView(this)*/);
}
}

package org.pumpkin.pumpkintutor2gsls.tutor2.triangle1;

import android.content.Context;
import android.opengl.GLSurfaceView;

import org.pumpkin.pumpkintutor2gsls.tutor2.triangle.TriangleRenderer;

/**
* Project name : PumpKinTutor2Gsls
* Created by zhibao.liu on 2016/5/18.
* Time : 11:18
* Email warden_sprite@foxmail.com
* Action : durian
*/
public class TriangleSurfaceView1 extends GLSurfaceView {

public TriangleSurfaceView1(Context context) {
super(context);

this.setEGLContextClientVersion(2);

//fix for error No Config chosen, but I don't know what this does.
super.setEGLConfigChooser(8 , 8, 8, 8, 16, 0);

this.setRenderer(new TriangleRenderer1(context));
// Render the view only when there is a change in the drawing data
setRenderMode(GLSurfaceView.RENDERMODE_WHEN_DIRTY);

}

}

package org.pumpkin.pumpkintutor2gsls.tutor2.triangle1;

import android.content.Context;
import android.opengl.GLES20;
import android.opengl.GLSurfaceView;
import android.opengl.Matrix;
import android.os.SystemClock;

import org.pumpkin.pumpkintutor2gsls.tutor2.coord.Coord;

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

/**
* Project name : PumpKinTutor2Gsls
* Created by zhibao.liu on 2016/5/18.
* Time : 11:17
* Email warden_sprite@foxmail.com
* Action : durian
*/
public class TriangleRenderer1 implements GLSurfaceView.Renderer {

private float[] mMVPMatrix = new float[16];
private float[] mViewMatrix = new float[16];
private float[] mModelMatrix = new float[16];
private float[] mProjectionMatrix = new float[16];

private Context mContext;
private Triangle1 triangle1;
private Coord coord;

public TriangleRenderer1(Context context) {
mContext = context;
}

@Override
public void onSurfaceCreated(GL10 gl, EGLConfig config) {

GLES20.glClearColor(0.0f, 0.0f, 0.0f, 1.0f);

GLES20.glEnable(GLES20.GL_CULL_FACE);
GLES20.glEnable(GLES20.GL_DEPTH_TEST);

triangle1 = new Triangle1(mContext);
triangle1.loadTexture();

coord = new Coord(mContext);

// Position the eye behind the origin.
final float eyeX = 0.0f;
final float eyeY = 0.0f;
final float eyeZ = 0.0f;

// We are looking toward the distance
final float lookX = 0.0f;
final float lookY = 0.0f;
final float lookZ = -1.0f;

// Set our up vector. This is where our head would be pointing were we holding the camera.
final float upX = 0.0f;
final float upY = 1.0f;
final float upZ = 0.0f;

// Set the view matrix. This matrix can be said to represent the camera position.
// NOTE: In OpenGL 1, a ModelView matrix is used, which is a combination of a model and
// view matrix. In OpenGL 2, we can keep track of these matrices separately if we choose.
Matrix.setLookAtM(mViewMatrix, 0, eyeX, eyeY, eyeZ, lookX, lookY, lookZ, upX, upY, upZ);

}

@Override
public void onSurfaceChanged(GL10 gl, int width, int height) {

GLES20.glViewport(0, 0, width, height);

final float ratio = (float) width / height;
final float left = -ratio;
final float right = ratio;
final float bottom = -1.0f;
final float top = 1.0f;
final float near = 1.0f;
final float far = 10.0f;

Matrix.frustumM(mProjectionMatrix, 0, left, right, bottom, top, near, far);

}

@Override
public void onDrawFrame(GL10 gl) {

GLES20.glClear(GLES20.GL_COLOR_BUFFER_BIT | GLES20.GL_DEPTH_BUFFER_BIT);

Matrix.setIdentityM(mModelMatrix, 0);
Matrix.translateM(mModelMatrix, 0, 0.0f, 0.0f, -5.0f);

Matrix.multiplyMM(mMVPMatrix, 0, mViewMatrix, 0, mModelMatrix, 0);
Matrix.multiplyMM(mMVPMatrix, 0, mProjectionMatrix, 0, mMVPMatrix, 0);

triangle1.draw(mMVPMatrix);
coord.draw(mMVPMatrix);

}

}

在上面的渲染器中,调整setLookAtM参数,以及frustumM参数,在运行既可以发现视角在变化.

package org.pumpkin.pumpkintutor2gsls.tutor2.triangle1;

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.opengl.GLES20;
import android.opengl.GLUtils;

import org.pumpkin.pumpkintutor2gsls.R;
import org.pumpkin.pumpkintutor2gsls.shader.PumpKinShader;

import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import java.nio.FloatBuffer;

/**
* Project name : PumpKinTutor2Gsls
* Created by zhibao.liu on 2016/5/18.
* Time : 11:17
* Email warden_sprite@foxmail.com
* Action : durian
*/
public class Triangle1 {

private FloatBuffer vertexsBuffer;
private FloatBuffer colorsBuffer;
private FloatBuffer texturesBuffer;

private int mMVPMatrixHandle;
private int mPositionHandle;
private int mColorHandle;
private int mTextureCoordsHandle;
private int mProgram;

private Context mContext;
private Bitmap bitmap;

private int[] textures=new int[1];

private float vertexs[]={
0.0f,0.0f,0.0f,
2.0f,0.0f,0.0f,
0.0f,2.0f,0.0f
};

private float colors[]={
1.0f,0.0f,0.0f,1.0f,
0.0f,1.0f,0.0f,1.0f,
0.0f,0.0f,1.0f,1.0f
};

private float textureCoords[]={
/*0,0,
1,0,
0,1*/
0,1,
1,0,
0,0
};

public Triangle1(Context context){

mContext=context;

ByteBuffer vbb=ByteBuffer.allocateDirect(vertexs.length*4);
vbb.order(ByteOrder.nativeOrder());
vertexsBuffer=vbb.asFloatBuffer();
vertexsBuffer.put(vertexs);
vertexsBuffer.position(0);

ByteBuffer cbb=ByteBuffer.allocateDirect(colors.length*4);
cbb.order(ByteOrder.nativeOrder());
colorsBuffer=cbb.asFloatBuffer();
colorsBuffer.put(colors);
colorsBuffer.position(0);

ByteBuffer tbb=ByteBuffer.allocateDirect(textureCoords.length*4);
tbb.order(ByteOrder.nativeOrder());
texturesBuffer=tbb.asFloatBuffer();
texturesBuffer.put(textureCoords);
texturesBuffer.position(0);

String vshaderCode= PumpKinShader.loadGsls(mContext,0);
String fshaderCode=PumpKinShader.loadGsls(mContext,1);

int mvShaderHandle= GLES20.glCreateShader(GLES20.GL_VERTEX_SHADER);
if(mvShaderHandle!=0) {
GLES20.glShaderSource(mvShaderHandle, vshaderCode);
GLES20.glCompileShader(mvShaderHandle);

int[] status=new int[1];
GLES20.glGetShaderiv(mvShaderHandle,GLES20.GL_COMPILE_STATUS,status,0);
if(status[0]==0){
GLES20.glDeleteShader(mvShaderHandle);
mvShaderHandle=0;
}

}

if(mvShaderHandle==0){
throw new RuntimeException("failed to create vertex shader !");
}

int mfShaderHandle=GLES20.glCreateShader(GLES20.GL_FRAGMENT_SHADER);
if(mfShaderHandle!=0){
GLES20.glShaderSource(mfShaderHandle,fshaderCode);
GLES20.glCompileShader(mfShaderHandle);

int[] status=new int[1];
GLES20.glGetShaderiv(mfShaderHandle,GLES20.GL_COMPILE_STATUS,status,0);
if(status[0]==0){
GLES20.glDeleteShader(mfShaderHandle);
mfShaderHandle=0;
}

}

if(mfShaderHandle==0){
throw new RuntimeException("failed to create fragment shader !");
}

mProgram=GLES20.glCreateProgram();
if(mProgram!=0){

GLES20.glAttachShader(mProgram,mvShaderHandle);
GLES20.glAttachShader(mProgram,mfShaderHandle);

GLES20.glLinkProgram(mProgram);

int[] linkstatus=new int[1];
GLES20.glGetProgramiv(mProgram,GLES20.GL_LINK_STATUS,linkstatus,0);
if(linkstatus[0]==0){

GLES20.glDeleteProgram(mProgram);
mProgram=0;

}

}

if(mProgram==0){
throw new RuntimeException("failed to create program !");
}

}

public void draw(float[] mvpmatrix){

GLES20.glUseProgram(mProgram);

mPositionHandle=GLES20.glGetAttribLocation(mProgram,"a_Position");
GLES20.glVertexAttribPointer(mPositionHandle,3,GLES20.GL_FLOAT,false,0,vertexsBuffer);
GLES20.glEnableVertexAttribArray(mPositionHandle);

mColorHandle=GLES20.glGetAttribLocation(mProgram,"a_Color");
GLES20.glVertexAttribPointer(mColorHandle,4,GLES20.GL_FLOAT,false,0,colorsBuffer);
GLES20.glEnableVertexAttribArray(mColorHandle);

mTextureCoordsHandle=GLES20.glGetAttribLocation(mProgram,"a_inputTextureCoordinate");
GLES20.glVertexAttribPointer(mTextureCoordsHandle,2,GLES20.GL_FLOAT,false,0,texturesBuffer);
GLES20.glEnableVertexAttribArray(mTextureCoordsHandle);

mMVPMatrixHandle=GLES20.glGetUniformLocation(mProgram,"u_MVPMatrix");
PumpKinShader.checkGLError("glGetUniformLocation");
GLES20.glUniformMatrix4fv(mMVPMatrixHandle,1,false,mvpmatrix,0);
PumpKinShader.checkGLError("glUniformMatrix4fv");

GLES20.glDrawArrays(GLES20.GL_TRIANGLE_STRIP,0,3);

GLES20.glDisableVertexAttribArray(mPositionHandle);
GLES20.glDisableVertexAttribArray(mColorHandle);
GLES20.glDisableVertexAttribArray(mTextureCoordsHandle);
GLES20.glBindTexture(GLES20.GL_TEXTURE_2D,0);
GLES20.glDisable(GLES20.GL_BLEND);

}

public void loadTexture(){

GLES20.glGenTextures(1,textures,0);
GLES20.glBindTexture(GLES20.GL_TEXTURE_2D,textures[0]);
GLES20.glTexParameterf(GLES20.GL_TEXTURE_2D,GLES20.GL_TEXTURE_MAG_FILTER,GLES20.GL_LINEAR);
GLES20.glTexParameterf(GLES20.GL_TEXTURE_2D,GLES20.GL_TEXTURE_MIN_FILTER,GLES20.GL_LINEAR);
GLES20.glTexParameterf(GLES20.GL_TEXTURE_2D,GLES20.GL_TEXTURE_WRAP_S,GLES20.GL_CLAMP_TO_EDGE);
GLES20.glTexParameterf(GLES20.GL_TEXTURE_2D,GLES20.GL_TEXTURE_WRAP_T,GLES20.GL_CLAMP_TO_EDGE);

bitmap= BitmapFactory.decodeResource(mContext.getResources(), R.drawable.src);
GLUtils.texImage2D(GLES20.GL_TEXTURE_2D,0,bitmap,0);

}

}

辅助类:

package org.pumpkin.pumpkintutor2gsls.shader;

import android.content.Context;
import android.opengl.GLES20;
import android.util.Log;

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

/**
* Project name : PumpKinBasicGLSL
* Created by zhibao.liu on 2016/5/11.
* Time : 14:26
* Email warden_sprite@foxmail.com
* Action : durian
*/
public class PumpKinShader {

private final static String TAG="PumpKinShader";

private static int GLESVersion=20;

public static void setVersion(int version){

switch (version){
case 20:
GLESVersion=20;
break;
case 30:
GLESVersion=30;
break;
default:
GLESVersion=20;
break;
}

}

public static String loadGsls(Context context, int type){

String shadercode="";
String shaderfilename="";
switch (type){
case 0:
shaderfilename="vshader.glsl";
break;
case 1:
shaderfilename="fshader.glsl";
break;
case 2:
shaderfilename="tvshader.glsl";
break;
case 3:
shaderfilename="tfshader.glsl";
break;
case 4:
shaderfilename="coordvshader.glsl";
break;
case 5:
shaderfilename="coordfshader.glsl";
break;
}

try {
InputStream is=context.getResources().getAssets().open(shaderfilename);
int length=is.available();
byte[] buffer=new byte[length];
int read = is.read(buffer);
shadercode=new String(buffer);//buffer.toString();
} catch (IOException e) {
e.printStackTrace();
}

Log.i(TAG,"shadercode : "+shadercode);

return shadercode;
}

public static int loadShader(int type,String shadercode){

int shader= GLES20.glCreateShader(type);

GLES20.glShaderSource(shader,shadercode);
GLES20.glCompileShader(shader);

return shader;

}

public static void checkGLError(String glOperation){
int error;
while((error=GLES20.glGetError())!=GLES20.GL_NO_ERROR){
throw new RuntimeException(glOperation+" : glError "+error);
}
}

}

同样增加一个坐标显示:

package org.pumpkin.pumpkintutor2gsls.tutor2.coord;

import android.content.Context;
import android.opengl.GLES20;

import org.pumpkin.pumpkintutor2gsls.shader.PumpKinShader;

import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import java.nio.FloatBuffer;

/**
* Project name : PumpKinTutor2Gsls
* Created by zhibao.liu on 2016/5/18.
* Time : 15:36
* Email warden_sprite@foxmail.com
* Action : durian
*/
public class Coord {

private FloatBuffer vertexsBuffer;
private FloatBuffer colorsBuffer;

private int mPositionHandle;
private int mColorHandle;
private int mMVPMatrixHandle;
private int mProgram;

private Context mContext;

private float[] vertexs={
0,0,0,
5,0,0,
0,0,0,
0,5,0,
0,0,0,
0,0,5
};

private float[] colors={
1.0f,0.0f,0.0f,1.0f,
1.0f,0.0f,0.0f,1.0f,
0.0f,1.0f,0.0f,1.0f,
0.0f,1.0f,0.0f,1.0f,
0.0f,0.0f,1.0f,1.0f,
0.0f,0.0f,1.0f,1.0f
};

public Coord(Context context){

mContext=context;

ByteBuffer vbb=ByteBuffer.allocateDirect(vertexs.length*4);
vbb.order(ByteOrder.nativeOrder());
vertexsBuffer=vbb.asFloatBuffer();
vertexsBuffer.put(vertexs);
vertexsBuffer.position(0);

ByteBuffer cbb=ByteBuffer.allocateDirect(colors.length*4);
cbb.order(ByteOrder.nativeOrder());
colorsBuffer=cbb.asFloatBuffer();
colorsBuffer.put(colors);
colorsBuffer.position(0);

String vshaderCode= PumpKinShader.loadGsls(mContext,4);
String fshaderCode=PumpKinShader.loadGsls(mContext,5);

int vshaderHandle=GLES20.glCreateShader(GLES20.GL_VERTEX_SHADER);
if(vshaderHandle!=0){

GLES20.glShaderSource(vshaderHandle,vshaderCode);
GLES20.glCompileShader(vshaderHandle);

int[] status=new int[1];
GLES20.glGetShaderiv(vshaderHandle,GLES20.GL_COMPILE_STATUS,status,0);
if(status[0]==0){
GLES20.glDeleteShader(vshaderHandle);
vshaderHandle=0;
}

}

int fshaderHandle=GLES20.glCreateShader(GLES20.GL_FRAGMENT_SHADER);
if(fshaderHandle!=0){

GLES20.glShaderSource(fshaderHandle,fshaderCode);
GLES20.glCompileShader(fshaderHandle);

int[] status=new int[1];
GLES20.glGetShaderiv(fshaderHandle,GLES20.GL_COMPILE_STATUS,status,0);
if(status[0]==0){
GLES20.glDeleteShader(fshaderHandle);
fshaderHandle=0;
}

}

if(fshaderHandle==0){
throw new RuntimeException("failed to create frag shader !");
}

mProgram=GLES20.glCreateProgram();
if(mProgram!=0){

GLES20.glAttachShader(mProgram,vshaderHandle);
GLES20.glAttachShader(mProgram,fshaderHandle);

GLES20.glLinkProgram(mProgram);

int[] linkstatus=new int[1];
GLES20.glGetProgramiv(mProgram,GLES20.GL_LINK_STATUS,linkstatus,0);
if(linkstatus[0]==0){
GLES20.glDeleteProgram(mProgram);
mProgram=0;
}

}

if(mProgram==0){
throw new RuntimeException("failed to create program !");
}

}

public void draw(float[] mvpMatrix){

GLES20.glUseProgram(mProgram);

mPositionHandle=GLES20.glGetAttribLocation(mProgram,"a_Position");
GLES20.glVertexAttribPointer(mPositionHandle,3,GLES20.GL_FLOAT,false,0,vertexsBuffer);
GLES20.glEnableVertexAttribArray(mPositionHandle);

mColorHandle=GLES20.glGetAttribLocation(mProgram,"a_Color");
GLES20.glVertexAttribPointer(mColorHandle,4,GLES20.GL_FLOAT,false,0,colorsBuffer);
GLES20.glEnableVertexAttribArray(mColorHandle);

mMVPMatrixHandle=GLES20.glGetUniformLocation(mProgram,"u_MvpMatrix");
PumpKinShader.checkGLError("glGetUniformLocation");
GLES20.glUniformMatrix4fv(mMVPMatrixHandle,1,false,mvpMatrix,0);
PumpKinShader.checkGLError("glUniformMatrix4fv");

GLES20.glDrawArrays(GLES20.GL_LINES,0,vertexs.length/3);

GLES20.glDisableVertexAttribArray(mColorHandle);
GLES20.glDisableVertexAttribArray(mPositionHandle);

}

}

下面是glsl脚本:



vshader.glsl :

uniform mat4 u_MVPMatrix;
uniform vec4 u_Color;
attribute vec4 a_Position;
attribute vec4 a_Color;
attribute vec4 a_inputTextureCoordinate;
varying vec2 textureCoordinate;
varying vec4 v_Color;
void main(){
gl_Position=u_MVPMatrix*a_Position;
v_Color=a_Color;
textureCoordinate=a_inputTextureCoordinate.xy;
}

gshader.glsl :

precision mediump float;
varying vec4 v_Color;
varying highp vec2 textureCoordinate;
uniform sampler2D inputImageTexture;
void main(){
gl_FragColor=v_Color*texture2D(inputImageTexture,textureCoordinate);
}

坐标对应的glsl脚本:

coordvshader.glsl:

uniform mat4 u_MvpMatrix;
attribute vec4 a_Position;
attribute vec4 a_Color;
varying vec4 v_Color;
void main() {

gl_Position=u_MvpMatrix*a_Position;
v_Color=a_Color;

}

coordfshader.glsl :

precision mediump float;
varying vec4 v_Color;
void main() {

gl_FragColor=v_Color;

}

另外在drawable下面增加一个src.png的图片/

运行结果:



最后:下载Nate Robin tutors-win32.zip这个包,里面有3D模拟器,可以通过3D模拟器参数设置观察效果,从而进一步理解上面的理论.这个模拟器可以说是神器啊!