To apply an edge effect to a 3D virtual object, a display system receives user input indicative of a desired display region of a 3D virtual object, defines a bounding volume corresponding to the desired display region, and clips the edges of the 3D virtual object to the surfaces of the bounding volume. The display system applies a visual edge effect to one or more of the clipped edges of the 3D virtual object, and displays to the user of the 3D virtual object with the visual edge effect. The technique can include selectively discarding pixels along a surface of the bounding volume, based on a depth map indicative of height values of the 3D virtual object at different horizontal pixel coordinates where the visual edge effect is applied only for edge pixels not discarded.