/// <summary>
/// Retrieves the angle, expressed in radians, between the two specified vectors.
/// </summary>
/// <param name="vector1">The first vector to evaluate.</param>
/// <param name="vector2">The second vector to evaluate.</param>
/// <returns>The angle, in radians, between vector1 and vector2.</returns>
public static float AngleBetween(VectorF vector1, VectorF vector2)
{
vector1.Normalize();
vector2.Normalize();
double angle = Math.Atan2(vector2.y, vector2.x) - Math.Atan2(vector1.y, vector1.x);
if (angle > Math.PI)
{
angle -= Math.PI * 2.0;
}
else if (angle < -Math.PI)
{
angle += Math.PI * 2.0;
}
return (float)angle;
}
/// <summary>
/// Start the inertia processor in Surface screen space.
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
private void OnAffine2DManipulationCompleted(object sender, Manipulation2DCompletedEventArgs e)
{
if (inertiaProcessor != null)
{
inertiaProcessor.Delta -= OnAffine2DInertiaDelta;
inertiaProcessor.Completed -= OnAffine2DInertiaCompleted;
inertiaProcessor.Complete(stopwatch.Elapsed100Nanoseconds());
}
VectorF translation = new VectorF(e.Total.TranslationX, e.Total.TranslationY);
// Don't start inertia if the tranlation is less than roughly 1/8" regardless of velocity.
if (translation.Length < 96 / 8f)
{
return;
}
// Scroll in the opposite direction because a ScrollViewer moves with the touch.
VectorF initialVelocity = new VectorF(-e.Velocities.LinearVelocityX, -e.Velocities.LinearVelocityY);
// Check velocity.
if (initialVelocity.Length < FlickUtilities.MinimumFlickVelocity)
{
// If velocity is below this threshold ignore it.
return;
}
if (initialVelocity.Length >= FlickUtilities.MaximumFlickVelocity)
{
// If velocity is too large, reduce it to a reasonable value.
initialVelocity.Normalize();
initialVelocity = FlickUtilities.MaximumFlickVelocity * initialVelocity;
}
processInertia = true;
inertiaProcessor = new InertiaProcessor2D();
inertiaProcessor.Delta += OnAffine2DInertiaDelta;
inertiaProcessor.Completed += OnAffine2DInertiaCompleted;
inertiaProcessor.TranslationBehavior = new InertiaTranslationBehavior2D
{
DesiredDisplacement = ConvertFromVerticalValueToScreenSpace(VerticalViewportSize),
InitialVelocityX = initialVelocity.X * HorizontalViewportSize,
InitialVelocityY = initialVelocity.Y * VerticalViewportSize
};
inertiaProcessor.InitialOriginX = ConvertFromHorizontalValueToScreenSpace(horizontalScrollBarStateMachine.Value);
inertiaProcessor.InitialOriginY = ConvertFromVerticalValueToScreenSpace(verticalScrollBarStateMachine.Value);
}
