Opengl ES 2.0 Android-根据旋转来平移相机

Question

I have an island random generation app for Android, developed with Opengl ES 2.0 and i am trying to implement an FPS-like camera. The main problem is to translate the view according to the camera rotation.This is how i rotate and translate the view:

    Matrix.setIdentityM(mCurrentRotation, 0);
    Matrix.rotateM(mCurrentRotation, 0, mAngleX, 0.0f,1.0f, 0.0f);
    Matrix.setIdentityM(mCurrentTranslation, 0);
    Matrix.translateM(mCurrentTranslation,0,xrot,-7.0f,yrot);
    mAngleX = 0.0f;

    Matrix.multiplyMM(mTemporaryMatrix, 0, mCurrentRotation, 0, mAccumulatedRotation, 0);

    System.arraycopy(mTemporaryMatrix, 0, mAccumulatedRotation, 0, 16);
          .
          .
          .
    Matrix.multiplyMM(mMVPMatrix, 0, mViewMatrix, 0, mModelMatrix, 0);
    Matrix.multiplyMM(mMVPMatrix, 0, mCurrentTranslation, 0, mMVPMatrix, 0);
    Matrix.multiplyMM(mMVPMatrix, 0, mTemporaryMatrix, 0, mMVPMatrix, 0);
    // This multiplies the modelview matrix by the projection matrix, and stores the result in the MVP matrix
    // (which now contains model * view * projection).
    Matrix.multiplyMM(mMVPMatrix, 0, mProjectionMatrix, 0, mMVPMatrix, 0);

Where mTemporaryMatrix stores the rotation of the camera on a given frame based on the old rotation and mAngleX that is a touch input. Same for mCurrentTranslation and xrot , yrot . So when i move around after a rotation the movement keeps being according to the world coordinates. My xrot,yrot update equation are the following:

  void setXYrot(float x, float y){
      Matrix.transposeM(temp,0,mTemporaryMatrix,0);
      Matrix.invertM(temp,0,temp,0);
      xrot-=(x*Math.sin(Math.acos(temp[5])));
      yrot+=(y*Math.cos(Math.acos(temp[5])));
  }

I am quite sure the problem relies on them. I transpose and invert the rotation matrix and then I take arccosine the sixth element of the matrix that should be the rotation on the Y-axis. Does someone see a bug somewhere in the update function? But mostly there is a standard way to do it?

Answer 1

Found the bug. First of all I keep the cumulative amount of mAngleX I rotate in a float variable called angle, and then simply:

void setXYrot(float x, float y){

    xrot-=(y*Math.sin((angle*Math.PI)/180f))+(x*Math.cos((angle*Math.PI)/180f));
    yrot+=(y*Math.cos((a*Math.PI)/180f))-(x*Math.sin((angle*Math.PI)/180f));
}

Works like a charme