How to use blueprints to select objects in the scene

[Supremative]

You could use Box Selection in HUD.

Look at this post (2d):

Draw Rectangle in World Space? (Box Selection)

[BoxSelection_2d_3d] Red rectangle - 2d selection (HUD). Blue rectangle - 3d selection area. Download Example Left Mouse Button - 2d. Right Mouse Button - 3d. [Pawn_Events] [HUD_Events] For 3d, I prepared only the selection area. You should think about implementing a selection of actors in 3d mode. [Pawn_Events_3dPlane] My Products