When using a Popup with PopupAnimation="Slide" and Placement="Top", the animation behavior in NoesisGUI differs from WPF.

In WPF, the popup initially appears just below the PlacementTarget and slides upward into its final position. This creates the visual effect that the popup emerges from the target element.

In NoesisGUI, the popup is initially positioned well above the PlacementTarget and slides downward to its final position. This makes the animation appear detached from the target and visually less natural.

For all other tested placement values, both WPF and NoesisGUI slide from top to bottom and behave consistently.

I've attached a simple slowed down video comparison of WPF and NoesisGUI.