openGL ES进阶教程（五）制作一个简单的VR播放器，播放全景视频

之前写过全景（VR）图片，和用openGL ES+MediaPlayer 渲染播放视频+滤镜效果

这一篇就在之前的基础上实现一个最简单的VR播放器，播放全景视频。

概述：

全景视频是一种用3D摄像机进行全方位360度进行拍摄的视频，用户在观看视频的时候，可以随意调节视频上下左右进行观看。

展示：

“身临其境的枪战” 可见晃动手机，视图也跟着转！

原理：

1.用OpenGL绘制一个球。
2.MediaPlayer 播放的视频纹理贴到球上（可以想象为一个地球仪）。
3.把观测点设置在求内部。 （想象为从球内部中心点观看球的表面）。
4.用手机内置的传感器得到一个手机移动的矩阵（视频画面就可以随着手机的移动而移动了）。

实践：

1.用OpenGL绘制一个球
效果如图：

用OpenGL绘制任何图形，都需要先知道顶点坐标。然后用GLES20.glDrawArrays绘制出来。
那么绘制一个球体，可以想象为无数个三角形在三维空间构成。
下面这个算法就会放回一个球体的坐标数组

 private float[] createBallPos(){        //球以(0,0,0)为中心，以R为半径，则球上任意一点的坐标为        // ( R * cos(a) * sin(b),y0 = R * sin(a),R * cos(a) * cos(b))        // 其中，a为圆心到点的线段与xz平面的夹角，b为圆心到点的线段在xz平面的投影与z轴的夹角        ArrayList<Float> data=new ArrayList<>();        float r1,r2;        float h1,h2;        float sin,cos;        for(float i=-90;i<90+step;i+=step){            r1 = (float)Math.cos(i * Math.PI / 180.0);            r2 = (float)Math.cos((i + step) * Math.PI / 180.0);            h1 = (float)Math.sin(i * Math.PI / 180.0);            h2 = (float)Math.sin((i + step) * Math.PI / 180.0);            // 固定纬度, 360 度旋转遍历一条纬线            float step2=step*2;            for (float j = 0.0f; j <360.0f+step; j +=step2 ) {                cos = (float) Math.cos(j * Math.PI / 180.0);                sin = -(float) Math.sin(j * Math.PI / 180.0);                data.add(r2 * cos);                data.add(h2);                data.add(r2 * sin);                data.add(r1 * cos);                data.add(h1);                data.add(r1 * sin);            }        }        float[] f=new float[data.size()];        for(int i=0;i<f.length;i++){            f[i]=data.get(i);        }        return f;    }

然后把坐标传给natave层

  float[] dataPos=createBallPos();        vertexBuffer = ByteBuffer.allocateDirect(dataPos.length * 4)                .order(ByteOrder.nativeOrder())                .asFloatBuffer()                .put(dataPos);        vertexBuffer.position(0);        vSize=dataPos.length/3;

有了坐标就可以绘制球了。

2.MediaPlayer 播放的视频纹理贴到球上（可以想象为一个地球仪）。

先贴着色器代码

attribute vec4 aPosition;//顶点位置attribute vec4 aTexCoord;//S T 纹理坐标varying vec2 vTexCoord;uniform mat4 uMatrix;uniform mat4 uSTMatrix;uniform mat4 uViewMatrix;uniform mat4 uModelMatrix;uniform mat4 uRotateMatrix;void main() {    vTexCoord = (uSTMatrix * aTexCoord).xy;    gl_Position = uMatrix*uRotateMatrix*uViewMatrix*uModelMatrix*aPosition;}

#extension GL_OES_EGL_image_external : requireprecision mediump float;varying vec2 vTexCoord;uniform samplerExternalOES sTexture;void main() {    gl_FragColor=texture2D(sTexture, vTexCoord);}

然后我们根据球的点把视频纹理贴到球上

        GLES20.glEnableVertexAttribArray(aPositionLocation);        GLES20.glVertexAttribPointer(aPositionLocation, 3, GLES20.GL_FLOAT, false,                0, posBuffer);        GLES20.glEnableVertexAttribArray(aTextureCoordLocation);        GLES20.glVertexAttribPointer(aTextureCoordLocation,2,GLES20.GL_FLOAT,false,0,cooBuffer);

绘制：

 GLES20.glDrawArrays(GLES20.GL_TRIANGLES, 0, vCount);

3.把观测点设置在求内部。 （想象为从球内部中心点观看球的表面）。

 //设置相机位置        Matrix.setLookAtM(mViewMatrix, 0, 0f, 0.0f,0.0f, 0.0f, 0.0f,-1.0f, 0f,-1.0f, 0.0f);

4.用手机内置的传感器得到一个手机移动的矩阵（视频画面就可以随着手机的移动而移动了）
在activity中

 @Override    public void onSensorChanged(SensorEvent sensorEvent) {        SensorManager.getRotationMatrixFromVector(matrix,sensorEvent.values);        glRenderer.setMatrix(matrix);    }

VRVideoRenderer 完整代码如下：

import android.content.Context;import android.graphics.SurfaceTexture;import android.media.AudioManager;import android.media.MediaPlayer;import android.net.Uri;import android.opengl.GLES11Ext;import android.opengl.GLES20;import android.opengl.GLSurfaceView;import android.opengl.Matrix;import android.util.Log;import android.view.Surface;import java.io.IOException;import java.nio.ByteBuffer;import java.nio.ByteOrder;import java.nio.FloatBuffer;import java.util.ArrayList;import javax.microedition.khronos.egl.EGLConfig;import javax.microedition.khronos.opengles.GL10;/** * Created by Shuo.Wang on 2017/4/19. */public class VRVideoRenderer implements GLSurfaceView.Renderer        , SurfaceTexture.OnFrameAvailableListener, MediaPlayer.OnVideoSizeChangedListener  {    private static final String TAG = "GLRenderer";    private static final float UNIT_SIZE = 1f;// 单位尺寸    private float radius=2f;    final double angleSpan = Math.PI/90f;// 将球进行单位切分的角度    int vCount = 0;// 顶点个数，先初始化为0    private FloatBuffer posBuffer;    private FloatBuffer cooBuffer;    private int mHViewMatrix;    private int mHModelMatrix;    private int mHRotateMatrix;    private float[] mViewMatrix=new float[16];    private float[] mModelMatrix=new float[16];    private float[] mRotateMatrix=new float[16];    private Context context;    private int aPositionLocation;    private int programId;    private FloatBuffer vertexBuffer;    private final float[] projectionMatrix=new float[16];    private int uMatrixLocation;    private FloatBuffer textureVertexBuffer;    private int uTextureSamplerLocation;    private int aTextureCoordLocation;    private int textureId;    private SurfaceTexture surfaceTexture;    private MediaPlayer mediaPlayer;    private float[] mSTMatrix = new float[16];    private int uSTMMatrixHandle;    private boolean updateSurface;    private boolean playerPrepared;    private int screenWidth,screenHeight;    public VRVideoRenderer(Context context, String videoPath) {        this.context = context;        playerPrepared=false;        synchronized(this) {            updateSurface = false;        }        calculateAttribute();        mediaPlayer=new MediaPlayer();        try{            mediaPlayer.setDataSource(context, Uri.parse(videoPath));        }catch (IOException e){            e.printStackTrace();        }        mediaPlayer.setAudioStreamType(AudioManager.STREAM_MUSIC);        mediaPlayer.setLooping(true);        mediaPlayer.setOnVideoSizeChangedListener(this);    }    @Override    public void onSurfaceCreated(GL10 gl, EGLConfig config) {        String vertexShader = ShaderUtils.readRawTextFile(context, R.raw.simple_vertex_shader);        String fragmentShader= ShaderUtils.readRawTextFile(context, R.raw.simple_fragment_shader);        programId=ShaderUtils.createProgram(vertexShader,fragmentShader);        aPositionLocation= GLES20.glGetAttribLocation(programId,"aPosition");        uMatrixLocation=GLES20.glGetUniformLocation(programId,"uMatrix");        uSTMMatrixHandle = GLES20.glGetUniformLocation(programId, "uSTMatrix");        mHViewMatrix=GLES20.glGetUniformLocation(programId,"uViewMatrix");        mHModelMatrix=GLES20.glGetUniformLocation(programId,"uModelMatrix");        mHRotateMatrix=GLES20.glGetUniformLocation(programId,"uRotateMatrix");        uTextureSamplerLocation=GLES20.glGetUniformLocation(programId,"sTexture");        aTextureCoordLocation=GLES20.glGetAttribLocation(programId,"aTexCoord");        int[] textures = new int[1];        GLES20.glGenTextures(1, textures, 0);        textureId = textures[0];        GLES20.glBindTexture(GLES11Ext.GL_TEXTURE_EXTERNAL_OES, textureId);        ShaderUtils.checkGlError("glBindTexture mTextureID");   /*GLES11Ext.GL_TEXTURE_EXTERNAL_OES的用处？      之前提到视频解码的输出格式是YUV的（YUV420p，应该是），那么这个扩展纹理的作用就是实现YUV格式到RGB的自动转化，      我们就不需要再为此写YUV转RGB的代码了*/        GLES20.glTexParameterf(GLES11Ext.GL_TEXTURE_EXTERNAL_OES, GLES20.GL_TEXTURE_MIN_FILTER,                GLES20.GL_NEAREST);        GLES20.glTexParameterf(GLES11Ext.GL_TEXTURE_EXTERNAL_OES, GLES20.GL_TEXTURE_MAG_FILTER,                GLES20.GL_LINEAR);        surfaceTexture = new SurfaceTexture(textureId);        surfaceTexture.setOnFrameAvailableListener(this);//监听是否有新的一帧数据到来        Surface surface = new Surface(surfaceTexture);        mediaPlayer.setSurface(surface);        surface.release();        if (!playerPrepared){            try {                mediaPlayer.prepare();                playerPrepared=true;            } catch (IOException t) {                Log.e(TAG, "media player prepare failed");            }            mediaPlayer.start();            playerPrepared=true;        }    }    @Override    public void onSurfaceChanged(GL10 gl, int width, int height) {        Log.d(TAG, "onSurfaceChanged: "+width+" "+height);        screenWidth=width; screenHeight=height;        //计算宽高比        float ratio=(float)width/height;        //透视投影矩阵/视锥        MatrixHelper.perspectiveM(projectionMatrix,0,90,ratio,1f,500);        //设置相机位置        Matrix.setLookAtM(mViewMatrix, 0, 0f, 0.0f,0.0f, 0.0f, 0.0f,-1.0f, 0f,-1.0f, 0.0f);        //模型矩阵        Matrix.setIdentityM(mModelMatrix,0);        Matrix.rotateM(mModelMatrix,0,180f,1f,0f,0f);    }    @Override    public void onDrawFrame(GL10 gl) {        GLES20.glClear( GLES20.GL_DEPTH_BUFFER_BIT | GLES20.GL_COLOR_BUFFER_BIT);        synchronized (this){            if (updateSurface){                surfaceTexture.updateTexImage();//获取新数据                surfaceTexture.getTransformMatrix(mSTMatrix);//让新的纹理和纹理坐标系能够正确的对应,mSTMatrix的定义是和projectionMatrix完全一样的。                updateSurface = false;            }        }        GLES20.glUseProgram(programId);        GLES20.glUniformMatrix4fv(uMatrixLocation,1,false,projectionMatrix,0);        GLES20.glUniformMatrix4fv(uSTMMatrixHandle, 1, false, mSTMatrix, 0);        GLES20.glUniformMatrix4fv(mHViewMatrix,1,false,mViewMatrix,0);        GLES20.glUniformMatrix4fv(mHModelMatrix,1,false,mModelMatrix,0);        GLES20.glUniformMatrix4fv(mHRotateMatrix,1,false,mRotateMatrix,0);        GLES20.glEnableVertexAttribArray(aPositionLocation);        GLES20.glVertexAttribPointer(aPositionLocation, 3, GLES20.GL_FLOAT, false,                0, posBuffer);        GLES20.glEnableVertexAttribArray(aTextureCoordLocation);        GLES20.glVertexAttribPointer(aTextureCoordLocation,2,GLES20.GL_FLOAT,false,0,cooBuffer);        GLES20.glActiveTexture(GLES20.GL_TEXTURE0);        GLES20.glBindTexture(GLES11Ext.GL_TEXTURE_EXTERNAL_OES,textureId);        GLES20.glUniform1i(uTextureSamplerLocation,0);        GLES20.glViewport(0,0,screenWidth,screenHeight);        //GLES20.glDrawArrays(GLES20.GL_TRIANGLE_STRIP, 0, 4);        GLES20.glDrawArrays(GLES20.GL_TRIANGLES, 0, vCount);//added by wangshuo    }    @Override    synchronized public void onFrameAvailable(SurfaceTexture surface) {        updateSurface = true;    }    @Override    public void onVideoSizeChanged(MediaPlayer mp, int width, int height) {        Log.d(TAG, "onVideoSizeChanged: "+width+" "+height);        //updateProjection(width,height);    }    public MediaPlayer getMediaPlayer() {        return mediaPlayer;    }    public void setMatrix(float[] matrix){        System.arraycopy(matrix,0,mRotateMatrix,0,16);    }    private void calculateAttribute(){        ArrayList<Float> alVertix = new ArrayList<>();        ArrayList<Float> textureVertix = new ArrayList<>();        for (double vAngle = 0; vAngle < Math.PI; vAngle = vAngle + angleSpan){            for (double hAngle = 0; hAngle < 2*Math.PI; hAngle = hAngle + angleSpan){                float x0 = (float) (radius* Math.sin(vAngle) * Math.cos(hAngle));                float y0 = (float) (radius* Math.sin(vAngle) * Math.sin(hAngle));                float z0 = (float) (radius * Math.cos((vAngle)));                float x1 = (float) (radius* Math.sin(vAngle) * Math.cos(hAngle + angleSpan));                float y1 = (float) (radius* Math.sin(vAngle) * Math.sin(hAngle + angleSpan));                float z1 = (float) (radius * Math.cos(vAngle));                float x2 = (float) (radius* Math.sin(vAngle + angleSpan) * Math.cos(hAngle + angleSpan));                float y2 = (float) (radius* Math.sin(vAngle + angleSpan) * Math.sin(hAngle + angleSpan));                float z2 = (float) (radius * Math.cos(vAngle + angleSpan));                float x3 = (float) (radius* Math.sin(vAngle + angleSpan) * Math.cos(hAngle));                float y3 = (float) (radius* Math.sin(vAngle + angleSpan) * Math.sin(hAngle));                float z3 = (float) (radius * Math.cos(vAngle + angleSpan));                alVertix.add(x1);                alVertix.add(y1);                alVertix.add(z1);                alVertix.add(x0);                alVertix.add(y0);                alVertix.add(z0);                alVertix.add(x3);                alVertix.add(y3);                alVertix.add(z3);                float s0 = (float) (hAngle / Math.PI/2);                float s1 = (float) ((hAngle + angleSpan)/Math.PI/2);                float t0 = (float) (vAngle / Math.PI);                float t1 = (float) ((vAngle + angleSpan) / Math.PI);                textureVertix.add(s1);// x1 y1对应纹理坐标                textureVertix.add(t0);                textureVertix.add(s0);// x0 y0对应纹理坐标                textureVertix.add(t0);                textureVertix.add(s0);// x3 y3对应纹理坐标                textureVertix.add(t1);                alVertix.add(x1);                alVertix.add(y1);                alVertix.add(z1);                alVertix.add(x3);                alVertix.add(y3);                alVertix.add(z3);                alVertix.add(x2);                alVertix.add(y2);                alVertix.add(z2);                textureVertix.add(s1);// x1 y1对应纹理坐标                textureVertix.add(t0);                textureVertix.add(s0);// x3 y3对应纹理坐标                textureVertix.add(t1);                textureVertix.add(s1);// x2 y3对应纹理坐标                textureVertix.add(t1);            }        }        vCount = alVertix.size() / 3;        posBuffer = convertToFloatBuffer(alVertix);        cooBuffer=convertToFloatBuffer(textureVertix);    }    private FloatBuffer convertToFloatBuffer(ArrayList<Float> data){        float[] d=new float[data.size()];        for (int i=0;i<d.length;i++){            d[i]=data.get(i);        }        ByteBuffer buffer=ByteBuffer.allocateDirect(data.size()*4);        buffer.order(ByteOrder.nativeOrder());        FloatBuffer ret=buffer.asFloatBuffer();        ret.put(d);        ret.position(0);        return ret;    }}