Question

In Android OpenGL

it has the command setLookAtM to specific the position for the camera view

Matrix.setLookAtM(mViewMatrix, 0, eyeX, eyeY, eyeZ, lookX, lookY,
            lookZ, upX, upY, upZ);

If I rotate camera, by using command rotateM

Matrix.rotateM(mViewMatrix, 0 , angle , 0.0f, 1.0f, 0.0f);

Then, How could I get the ‘LookAt’ the exact camera view from mViewMatrix ?

the camera view position, i want is x,y,z that camera look at

Answer 1

I have finished my question
and this is my solution

first, I need to made this 3 matrix to get result of x, y, z position

private float[] mRotXMatrix = new float[] {
 1, 0, 0, 0, 
 0, 0, 1, 0,
 0, 1, 0, 0,
 0, 0, 0, 1 };
private float[] mRotYMatrix = new float[] {
 0, 0, 1, 0,
 0, 1, 0, 0,
 1, 0, 0, 0,
 0, 0, 0, 1 };
private float[] mRotZMatrix = new float[] { 
 0, 1, 0, 0,
 1, 0, 0, 0,
 0, 0, 1, 0,
 0, 0, 0, 1 };

Then in onSensorChanged(SensorEvent e) method I rotate all these 3 matrix together with my camera view like this

Matrix.multiplyMM(mViewMatrix, 0, deltaRotationMatrix, 0, mViewMatrix, 0);
Matrix.multiplyMM(mRotXMatrix, 0, deltaRotationMatrix, 0, mRotXMatrix, 0);
Matrix.multiplyMM(mRotYMatrix, 0, deltaRotationMatrix, 0, mRotYMatrix, 0);
Matrix.multiplyMM(mRotZMatrix, 0, deltaRotationMatrix, 0, mRotZMatrix, 0);

And to get the X, Y, Z of my camera view, just get it from these matrix

viewX = mRotXMatrix[2];
viewY = -mRotYMatrix[6]; // +/- up to your initial camera view
viewZ = mRotZMatrix[10];