If a point belonging to a model is deleted from Plan View, the lines and triangles associated with that point will also be deleted. The deleted points and their associated triangles will also be deleted from the 3D view.
Performing an Undo in Plan View after deleting a point will bring the point and its associated objects, such as lines and triangles, back into Plan View however this will not immediately be represented in 3D View.
The Regenerate Model button in 3D View will update the 3D view to reflect the changes made by pressing Undo in Plan View