I've tried solving this problem in bit simplier way, using accelerometer values only.
In activity class, onSensorChanged method:
@Override
public void onSensorChanged(SensorEvent event) {
if (event.sensor.getType() != Sensor.TYPE_ACCELEROMETER)
return;
/*
* record the accelerometer data, the event's timestamp as well as
* the current time. The latter is needed so we can calculate the
* "present" time during rendering. In this application, we need to
* take into account how the screen is rotated with respect to the
* sensors (which always return data in a coordinate space aligned
* to with the screen in its native orientation).
*/
switch (mDisplay.getRotation()) {
case Surface.ROTATION_0:
mSensorX = event.values[0];
mSensorY = event.values[1];
break;
case Surface.ROTATION_90:
mSensorX = -event.values[1];
mSensorY = event.values[0];
break;
case Surface.ROTATION_180:
mSensorX = -event.values[0];
mSensorY = -event.values[1];
break;
case Surface.ROTATION_270:
mSensorX = event.values[1];
mSensorY = -event.values[0];
break;
}
if (gameManager != null)
gameManager.handleSensor(mSensorX, mSensorY);
}
This method is mostly copied from Android sample ball game
gameManager is the instance of my game's class, which handles user input, game loop, creating game objects etc. gameManager.handleSensor(mSensorX, mSensorY) can be be replaced with your method handling accelerometer values.
Then goes GameManager class:
final int TICKS_PER_SECOND = 50;
final int SKIP_TICKS = 1000 / TICKS_PER_SECOND;
/**
* Game loop thread
* @author 32kda
*/
protected class GameLoop extends Thread {
public GameLoop() {
super("GameLoop");
}
@Override
public void run() {
long ticks = System.currentTimeMillis();
while (!isPaused()) {
long current = System.currentTimeMillis();
if (current - ticks < SKIP_TICKS) {
try {
sleep(SKIP_TICKS - (current - ticks));
} catch (InterruptedException e) {
e.printStackTrace();
}
}
updateGame(System.currentTimeMillis() - ticks); //Call update game method with some time interval
ticks = current;
}
super.run();
}
public boolean isPaused () {
return false;
}
}
...
final SimpleVector initialVectorUp = new SimpleVector(0f,-1f,0f); //Initial vector pointing up
SimpleVector vectorUp = new SimpleVector(0f,-1f,0f); //Camera's up vector. We reinit & rotate it any time we change camera orientation to set camera up/down angle with it
private float sensorX; //Accelerometer X & Y values
private float sensorY;
private float initialY = Float.MIN_VALUE; //field for storing initial y accelerometer value
private SimpleVector cameraVector = new SimpleVector(0f,0f,1f); //Camera horizontal orientation/azimuth vector
private SimpleVector orthoVector = new SimpleVector(); //Vector for rotating camera up/down. should be orthogonal to cameraVector when rotating
private Matrix cameraMatrix = new Matrix(); //Camera up vector rotation matrix
private float angle = 0; //Camera up/down rotation angle
/**
*handleSensor method. Simply remember sensorX / sensorY val for future use
*/
public void handleSensor(float mSensorX, float mSensorY) {
this.sensorX = mSensorX;
this.sensorY = mSensorY;
}
/**
*This method is called from game loop & used to update our world, camera, etc.
*/
protected void updateGame(long delta) {
if (Math.abs(sensorX) > 0.3) { //If x accelerometer value is greater than some threshold - rotate camera direction vector according to it
cameraVector.rotateY(-sensorX / 150);
}
Camera camera = world.getCamera();
if (initialY == Float.MIN_VALUE || initialY == 0.0) //Because it's not convenient to play with device placed strictly horizontally, I use some "initial" value
initialY = sensorY; //for vertical angle, and use it as position corresponding to zero vertical angle for camera
float yDiff = sensorY - initialY; //Calc the differnce
if (Math.abs(yDiff) > 0.3) {
angle -= yDiff / 200;
if (angle > 0.40f) //Limit vertical angle
angle = 0.40f;
if (angle < -0.40f)
angle = -0.40f;
}
vectorUp.set(initialVectorUp); //Re-init camera up-vector before rotating it to necessary angle
orthoVector.x = cameraVector.z; //Calculate vector orthogonal to camera vector (camera up/down riotation vector)
orthoVector.z = -cameraVector.x;
calcRotMatrix(cameraMatrix,orthoVector,angle); //Calculate rotation matrix
vectorUp.rotate(cameraMatrix); //rotate camera up vector
camera.setOrientation(cameraVector,vectorUp); //Set camera orientation
}
/**
* Calculates rotation matrix for arbitrary axis
* @param matrix Matrix to fill
* @param rotVector Arbitrary rotation axis vector
* @param angle Rotation angle
* Calculation algorythm got from the Internet & it works. Can't explain in details how(
*/
protected void calcRotMatrix(Matrix matrix, SimpleVector rotVector, float angle) {
matrix.setColumn(3,0,0,0,1);
matrix.setRow(3,0,0,0,1);
double sin = Math.sin(angle);
double cos = Math.cos(angle);
double subcos = 1 - cos;
float x = rotVector.x;
float y = rotVector.y;
float z = rotVector.z;
matrix.set(0,0,(float) (cos + subcos*x*x));
matrix.set(0,1,(float) (subcos*x*y - sin*z));
matrix.set(0,2,(float) (subcos*x*z + sin*y));
matrix.set(1,0,(float) (subcos*y*x + sin*z));
matrix.set(1,1,(float) (cos + subcos*y*y));
matrix.set(1,2,(float) (subcos*y*z - sin*x));
matrix.set(2,0,(float) (subcos*z*x - sin*y));
matrix.set(2,1,(float) (subcos*z*y + sin*x));
matrix.set(2,2,(float) (cos + subcos*z*z));
}
