/// <summary>
/// Converts the screen coordinates to world coordiantes using the specified attitude matrix.
/// </summary>
/// <param name="pointOnScreen">
/// The point in screen coordinates to translate.
/// </param>
/// <param name="attitude">
/// The attitude matrix to use for translations.
/// </param>
/// <returns>
/// A <see cref="Vector3"/> in world space.
/// </returns>
public Vector3 ScreenToWorld(Point pointOnScreen, Matrix attitude)
{
// Ensure that the viewport has been created
EnsureViewport();
// Use the attitude Matrix saved in the OnMouseLeftButtonUp handler.
// Rotate it 90 degrees around the X axis to put it in the XNA Framework coordinate system.
attitude = Matrix.CreateRotationX(MathHelper.PiOver2) * attitude;
// for the near point we specified zero as the z component of the point which means this point is as close as
// possible to the camera, while one for the second point means it’s as far as possible from the camera
Vector3 nearPoint = new Vector3((float)pointOnScreen.X, (float)pointOnScreen.Y, 0);
Vector3 farPoint = new Vector3((float)pointOnScreen.X, (float)pointOnScreen.Y, 1);
// Convert the near and far points from mouse space to 3D space
nearPoint = viewport.Unproject(nearPoint, projection, view, attitude);
farPoint = viewport.Unproject(farPoint, projection, view, attitude);
// Now that we have the near and far points in 3D space, create a directional vector between the two points
// and normalize it. Normalizing makes the vector only one unit in length but still pointing in the same
// direction.
Vector3 direction = farPoint - nearPoint;
direction.Normalize();
// Now we take our direction and multiply it by 10, which essentially just moves it out almost to the edge of
// our sceeen (our edge is 12 as defined by FarClippingPlane above). 10 units is also where all the labels like
// 'front', 'back', 'left', etc. are positioned. This way if the user taps on one of the labels, their new label
// will be at the same location and will move in sync.
Vector3 unprojected = direction * 10;
// Return the unprojected location
return(unprojected);
}
/// <summary>
/// Occurs when the value of the <see cref="Attitude"/> property has changed.
/// </summary>
/// <param name="e">
/// A <see cref="DependencyPropertyChangedEventArgs"/> containing event information.
/// </param>
protected override void OnAttitudeChanged(DependencyPropertyChangedEventArgs e)
{
base.OnAttitudeChanged(e);
// Ensure that the viewport has been created
EnsureViewport();
// Get the RotationMatrix from the MotionReading.
// Rotate it 90 degrees around the X axis to put it in the XNA Framework coordinate system.
Matrix xnaAttitude = Matrix.CreateRotationX(MathHelper.PiOver2) * Attitude;
// Loop through our items
for (int i = 0; i < Items.Count; i++)
{
// Get the WorldVIewItem that matches the index
WorldViewItem wvItem = ItemContainerGenerator.ContainerFromIndex(i) as WorldViewItem;
// If we couldn't get a WorldViewItem for the index, skip
if (wvItem == null)
{
continue;
}
// Get the ARItem that the WorldViewItem represents
ARItem arItem = (ARItem)wvItem.DataContext;
// Create a World matrix for the ARItems WorldLocation
Matrix world = Matrix.CreateWorld(arItem.WorldLocation, new Vector3(0, 0, 1), new Vector3(0, 1, 0));
// Use Viewport.Project to project the ARItems location in 3D space into screen coordinates
Vector3 projected = viewport.Project(Vector3.Zero, projection, view, world * xnaAttitude);
// If the point is outside of this range, it is behind the camera
if (projected.Z > 1 || projected.Z < 0)
{
// Out of range, just hide
wvItem.Visibility = Visibility.Collapsed;
}
else
{
// In range so show
wvItem.Visibility = Visibility.Visible;
/*
* // Create a TranslateTransform to position the WorldViewItem
* TranslateTransform tt = new TranslateTransform();
*
* // Offset by half of the WorldViewItems size to center it on the point
* tt.X = projected.X - (wvItem.ActualWidth / 2);
* tt.Y = projected.Y - (wvItem.ActualHeight / 2);
*
* // Set the transform, which moves the item
* wvItem.RenderTransform = tt;
*/
// Create a CompositeTransform to position and scale the WorldViewItem
CompositeTransform ct = new CompositeTransform();
// Offset by half of the WorldViewItems size to center it on the point
// TODO: Expose vertical limit property
#if WIN_RT
ct.TranslateX = projected.X - (wvItem.ActualWidth / 2) - (this.ActualWidth / 2);
// Ricky; Keep the y value within the screen
double y = projected.Y - (wvItem.ActualHeight / 2);
double h2 = this.Height / 2;
y = (y < -h2) ? -h2 : ((y > h2) ? h2 : y);
ct.TranslateY = y;
#endif
#if WINDOWS_PHONE
ct.TranslateX = projected.X - (wvItem.ActualWidth / 2);
ct.TranslateY = projected.Y - (wvItem.ActualHeight / 2);
#endif
#if WP7
double scale = MathHelper.Lerp((float)MinItemScale, (float)MaxItemScale, ((float)FarClippingPlane - Math.Abs(arItem.WorldLocation.Z)) / (float)FarClippingPlane);
#else
double scale = MathHelper.Lerp(MinItemScale, MaxItemScale, (FarClippingPlane - Math.Abs(arItem.WorldLocation.Z)) / FarClippingPlane);
#endif
ct.ScaleX = scale;
ct.ScaleY = scale;
// Set the transform, which moves the item
wvItem.RenderTransform = ct;
// Set the items z-index so that the closest item is always rendered on top
Canvas.SetZIndex(wvItem, (int)(scale * 255));
}
}
}