How to write MapView to OpenGL Texture

Question

Now, I'm trying to write MapView of GoogleMaps Android API to OpenGLES2.0 texture, and make the texture be displayed with OpenGL in Android Project.

But so far, I couldn't do that. It displays only Google Logo and background. The map isn't displayed.

What I tried are the following. 1) To make OpenGL texture. 2) To make SubClass of MapView, and write the Texture using overridden draw method. 3) To set the display area and rendered the texture in every frame, using GLSurfaceView.Renderer inherited class.

Do you know how to write GoogleMap to OpenGL Texture, and render that?

The following are the parts of my code have relevance to this matter.

－ It is the overridden draw method of MapView SubClass

@Override
 public void draw(Canvas canvas){
        final Canvas surfaceCanvas = surface.lockCanvas( null );
        super.draw(surfaceCanvas);
        surface.unlockCanvasAndPost( surfaceCanvas );
  }

－ GLSurfaceView.Renderer inherited Class（using Shader Class named GLES）

@Override
public void onSurfaceCreated(GL10 gl10,EGLConfig eglConfig) {
    GLES.makeProgram();        

    GLES20.glEnableVertexAttribArray(GLES.positionHandle);
    GLES20.glEnableVertexAttribArray(GLES.uvHandle);      

    GLES20.glEnable(GLES11Ext.GL_TEXTURE_EXTERNAL_OES);
    GLES20.glEnable(GLES20.GL_BLEND);    
    GLES20.glBlendFunc(GLES20.GL_SRC_ALPHA,
    GLES20.GL_ONE_MINUS_SRC_ALPHA);
    uvBuffer=makeUVBuffer();
 }

@Override
public void onSurfaceChanged(GL10 gl10,int w,int h) {
　　  surface = null;
　　  surfaceTexture = null;

      textureId=createTexture();

      GLES20.glViewport(0,0,w,h);
      screenW=w;
      screenH=h;

      vertexBuffer0=makeVertexBuffer(50,50,200,200);
      vertexBuffer1=makeVertexBuffer(50,300,300,300);

      if(textureId > 0){
        surfaceTexture = new SurfaceTexture( textureId );
        surfaceTexture.setDefaultBufferSize( 1134,  1134);
        GL20TextureEx1.surface = new Surface( surfaceTexture ); 
      }
}

@Override
 public void onDrawFrame(GL10 gl10) {
　   synchronized ( this ) {
                surfaceTexture.updateTexImage();
     }
     GLES20.glClearColor(0.5f,1.0f,1.0f,0.0f);
     GLES20.glClear(GLES20.GL_COLOR_BUFFER_BIT);

     GLES20.glActiveTexture(GLES20.GL_TEXTURE0);

     GLES20.glBindTexture(GLES11Ext.GL_TEXTURE_EXTERNAL_OES, textureId);

     GLES20.glUniform1i(GLES.texHandle,0);

     GLES20.glVertexAttribPointer(GLES.uvHandle,2,
        GLES20.GL_FLOAT,false,0,uvBuffer);

     GLES20.glVertexAttribPointer(GLES.positionHandle,3,
        GLES20.GL_FLOAT,false,0,vertexBuffer0);
     GLES20.glDrawArrays(GLES20.GL_TRIANGLE_STRIP,0,4);

     GLES20.glVertexAttribPointer(GLES.positionHandle,3,
        GLES20.GL_FLOAT,false,0,vertexBuffer1);
     GLES20.glDrawArrays(GLES20.GL_TRIANGLE_STRIP,0,4);
 }

N Dorigatti N Dorigatti · Accepted Answer · 2015-12-01T08:58:02

You can't take the map view and draw wherever you want unfortunately, you have to take a snapshot of the map and then render it. Unfortunately it is an async method, so It could be a problem for your Opengl ES application... Here an example on how to do an on request snapshot:

SnapshotReadyCallback callback = new SnapshotReadyCallback() {

                @Override
                public void onSnapshotReady(Bitmap snapshot) {
                    try {
                       //Your Snapshot is ready, do whatever you need Here! 
                    } catch (Exception e) {
                        e.printStackTrace();
                    }
                }
            };

            map.snapshot(callback);

How to write MapView to OpenGL Texture

1 Answers