public void UpdateRotation(VirtualObject virtualObject, CGPoint span)
{
var midPointToFirstTouch = span.Divide(2f);
var currentAngle = Math.Atan2(midPointToFirstTouch.X, midPointToFirstTouch.Y);
var currentAngleToInitialFingerAngle = InitialFingerAngle - currentAngle;
if (!RotationThresholdPassed)
{
var threshold = RotationThreshold;
if (TranslationThresholdPassed || ScaleThresholdPassed)
{
threshold = RotationThresholdHarder;
}
if ((float)Math.Abs(currentAngleToInitialFingerAngle) > threshold)
{
RotationThresholdPassed = true;
// Change the initial object angle to prevent a sudden jump after crossing the threshold.
if (currentAngleToInitialFingerAngle > 0f)
{
InitialObjectAngle += threshold;
}
else
{
InitialObjectAngle -= threshold;
}
}
}
if (RotationThresholdPassed)
{
// Note:
// For looking down on the object (99% of all use cases), we need to subtract the angle.
// To make rotation also work correctly when looking from below the object one would have to
// flip the sign of the angle depending on whether the object is above or below the camera...
var x = virtualObject.EulerAngles.X;
var y = InitialObjectAngle - currentAngleToInitialFingerAngle;
var z = virtualObject.EulerAngles.Z;
virtualObject.EulerAngles = new SCNVector3(x, (float)y, z);
LastUsedObject = virtualObject;
}
}