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:

http://blog.csdn.net/kesalin/article/details/7168967

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);

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);

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

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!

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

原文：http://blog.csdn.net/qq_31726827/article/details/51451737