CMMotionManager Reference Frame - ios

Question

I'm developing an app that when a user opens there will be an image, controlled by CMMotionManager, which moves according to the direction the user tilts the device.
....
This is my code to start the device motion.
motionManager = [[CMMotionManager alloc] init];
motionManager.showsDeviceMovementDisplay = YES;
motionManager.deviceMotionUpdateInterval = 1.0 / 60.0;
[motionManager startDeviceMotionUpdatesUsingReferenceFrame:CMAttitudeReferenceFrameXArbitraryCorrectedZVertical];
The is the code I use to control my image in reference to the motion of the device.
- (void)drawRect:(CGRect)rect
{
if (placesOfInterestCoordinates == nil) {
return;
}
mat4f_t projectionCameraTransform;
multiplyMatrixAndMatrix(projectionCameraTransform, projectionTransform, cameraTransform);
int i = 0;
for (MovingImage *poi in [placesOfInterest objectEnumerator]) {
vec4f_t v;
multiplyMatrixAndVector(v, projectionCameraTransform, placesOfInterestCoordinates[i]);
float x = (v[0] / v[3] + 1.0f) * 0.5f;
float y = (v[1] / v[3] + 1.0f) * 0.5f;
if (v[2] < 0.0f) {
CGPoint movingTo = CGPointMake(x*self.bounds.size.width, self.bounds.size.height-y*self.bounds.size.height);
if (movingTo.x < -118) {
movingTo.x = -118;
}
if (movingTo.x > 542) {
movingTo.x = 542;
}
if (movingTo.y < 215) {
movingTo.y = 215;
}
if (movingTo.y > 390) {
movingTo.y = 390;
}
poi.view.center = movingTo;
poi.view.hidden = NO;
} else {
poi.view.hidden = YES;
}
i++;
}
}
The image is in the middle of the screen rarely when the user opens the app, the image is usually to the right or left 90 degrees of the starting position, or exactly in the middle consistently.
I assume that CMAttitudeReferenceFrameXArbitraryCorrectedZVertical is the issue, but I have also tried CMAttitudeReferenceFrameXArbitraryZVertical which doesn't work either.
If useful, my project is here, for anyone interested. I used Apple pARk sample code as well.

Answer 1

- (void)drawRect:(CGRect)rect
{
if (placesOfInterestCoordinates == nil) {
return;
}
mat4f_t projectionCameraTransform;
multiplyMatrixAndMatrix(projectionCameraTransform, projectionTransform, cameraTransform);
int i = 0;
for (MovingImage *poi in [placesOfInterest objectEnumerator]) {
vec4f_t v;
multiplyMatrixAndVector(v, projectionCameraTransform, placesOfInterestCoordinates[i]);
float x = (v[0] / v[3] + 1.0f) * 0.5f;
float y = (v[1] / v[3] + 1.0f) * 0.5f;
if (v[2] < 1.0f) { // change here
CGPoint movingTo = CGPointMake(x*self.bounds.size.width, self.bounds.size.height-y*self.bounds.size.height);
if (movingTo.x < -118) {
movingTo.x = -118;
}
if (movingTo.x > 542) {
movingTo.x = 542;
}
if (movingTo.y < 215) {
movingTo.y = 215;
}
if (movingTo.y > 390) {
movingTo.y = 390;
}
poi.view.center = movingTo;
poi.view.hidden = NO;
} else {
poi.view.hidden = YES;
}
i++;
}
}
try changing (v[2] < 0.0f) to (v[2] < 1.0f)
The viewing angle is different because it is looking for when the image comes into view, other than your device's perspective angle.