Parameters
- mapView
- The view to add the overlay.
- graphic
- The graphic to be added to the overlay.
- referenceScale
- Map reference scale or -1
- showThrough
- Visibility factor for showing the overlay through other objects when obscured in 3D.
Valid range is [0..1], any other value will be treated as 0 (not visible).
Return Value
An object that when disposed will remove the overlay.