Android OpenGL ES 2.0投射触控位置

Question

我是Android的OpenGL ES 2.0新手，我想制作简单的应用程序来培养我的技能。我在投射位置时遇到问题。我在我的应用程序中绘制了一些正方形，我想要在触摸屏时检测到哪个方块。如果我不使用Model-View-Projection Matrix，一切都很简单，但是当我使用MVP Matrix时，我只是不明白它是如何工作的。这是一些代码： 在AngelicRenderer班：

    @Override
        public void onDrawFrame(GL10 unused)
        {
            GLES20.glClear(GLES20.GL_COLOR_BUFFER_BIT);
            // Set the camera position (View matrix)
            Matrix.setLookAtM(mViewMatrix, 0, 0f, 0f, 3f, 0f, 0f, 0f, 0f, 1f, 0f);

            // Calculate the projection and view transformation
            Matrix.multiplyMM(mMVPMatrix, 0, mProjectionMatrix, 0, mViewMatrix, 0);

            lock.lock();
            try
            {
                for(Entry> squares : getObjects())
                {
                    for(AngelicSquare square : squares.getValue())
                    {
                        square.draw(mMVPMatrix);
                    }
                }
            }
            finally
            {
                lock.unlock();
            }
        }
        @Override
        public void onSurfaceChanged(GL10 unused, int width, int height)
        {
            GLES20.glViewport(0, 0, width, height);

            float ratio = (float) width / height;
            screenWidth = width;
            screenHeight = height;

            // this projection matrix is applied to object coordinates
            // in the onDrawFrame() method
            Matrix.frustumM(mProjectionMatrix, 0, -ratio, ratio, -1f, 1f, 1f, 10f);
        }

在AngelicView类中，onTouchEvent：

    for(Entry> squares : devilishRenderer.getObjects())
    {
        for(AngelicSquare square : squares.getValue())
        {
            float[] coords = square.getPosition();
            float[] size = square.getSize();
            float[] touchPoint = { e.getX(), e.getY(), 0.0f, 0.0f };
            float[] touchPointNew = ViewCoordsToGLCoords(touchPoint);
            float[] topLeft = { coords[0], coords[1], 0.0f, 0.0f };
            Matrix.multiplyMV(topLeft, 0, devilishRenderer.getMVPMatrix(), 0, topLeft, 0);
            float[] bottomRight = { coords[0] + size[0], coords[1] - size[1], 0.0f, 0.0f };
            Matrix.multiplyMV(bottomRight, 0, devilishRenderer.getMVPMatrix(), 0, bottomRight, 0);
            Matrix.multiplyMV(touchPoint, 0, devilishRenderer.getMVPMatrix(), 0, touchPointNew, 0);

            if(touchPoint[0] > topLeft[0] && touchPoint[1]  bottomRight[1])
            {
                hookedSquare = square;
            }
        }
    }

如何使用模型 - 视图 - 投影矩阵将屏幕协调投影到OpenGL协调系统？