private void OnTilePointerPressed(object sender, PointerRoutedEventArgs e)
{
var tileGrid = (Grid)sender;
var colorElement = (Rectangle)tileGrid.FindName("ColorElement");
// Set the CenterPoint of the backing Visual, so the rotation axis will defined from the middle.
colorElement.Visual().CenterPoint = new Vector3(tileGrid.RenderSize.ToVector2() / 2, 0.0f);
// Calculate distance from corner of quadrant to Center
_center = colorElement.Visual().CenterPoint;
var xSquared = Math.Pow(tileGrid.ActualWidth / 2, 2);
var ySquared = Math.Pow(tileGrid.ActualHeight / 2, 2);
_distanceToCenter = (float)Math.Sqrt(xSquared + ySquared);
// || DEFINE THE EXPRESSION FOR THE ROTATION ANGLE ||
// We calculate the Rotation Angle such that it increases from 0 to 3 as the cursor position moves away from the center.
// Combined with animating the Rotation Axis, the image is "push down" on the point at which the cursor is located.
var pointerPositionProperties = ElementCompositionPreview.GetPointerPositionPropertySet(tileGrid);
var pointerPosition = pointerPositionProperties.GetSpecializedReference <PointerPositionPropertySetReferenceNode>().Position;
var angleExpressionNode = 3 * (EF.Clamp(EF.Distance(_center, pointerPosition), 0, _distanceToCenter) % _distanceToCenter / _distanceToCenter);
var rotationAngleAnimation = _compositor.CreateScalarKeyFrameAnimation();
rotationAngleAnimation.Duration = TimeSpan.FromMilliseconds(600);
rotationAngleAnimation.InsertExpressionKeyFrame(0.4f, angleExpressionNode);
rotationAngleAnimation.InsertKeyFrame(1.0f, 0.0f);
colorElement.Visual().StartAnimation("RotationAngleInDegrees", rotationAngleAnimation);
// || DEFINE THE EXPRESSION FOR THE ROTATION AXIS ||
// The RotationAxis will be defined as the axis perpendicular to vector position of the hover pointer (vector from center to hover position).
// The axis is a vector calculated by first converting the pointer position into the coordinate space where the center point (0, 0) is in the middle.
// The perpendicular axis is then calculated by transposing the cartesian x, y components and negating one (e.g. Vector3(-y,x,0) )
var axisAngleExpressionNode = EF.Floor((pointerPosition.X - _center.X) * EF.Conditional(pointerPosition.X == _center.X, 0, 1));
var rotationAxisAnimation = _compositor.CreateScalarKeyFrameAnimation();
rotationAxisAnimation.Duration = TimeSpan.FromMilliseconds(600);
rotationAxisAnimation.InsertExpressionKeyFrame(0.4f, axisAngleExpressionNode);
rotationAxisAnimation.InsertKeyFrame(1.0f, 0.0f);
colorElement.Visual().StartAnimation("RotationAxis.Y", rotationAxisAnimation);
}
