The projection view for 3D objects can be toggled between a Perspective View and an Orthographic View via the Toggle Perspective option on the Drawing Viewer toolbar.
The Perspective projection view gives a more realistic view as it is a better approximate representation of an object on a flat surface to what is seen by the eye in reality. Objects further away from the point of view are smaller and distances along the line of sight are foreshortened as the projections along the lines of sight converge on 'vanishing points'.
Perspective View
Orthographic View
Orthographic projection is a means of representing a 3 dimensional object on a 2 dimensional plane where the point of perspective is at infinite distance and the projections along the line of sight never converge. This can result in some shapes appearing distorted.