You can create realistic visual effects in a drawing by defining either parallel or perspective projections of a model.
The difference between perspective views and parallel projections is that perspective views require a distance between a theoretical camera and target point. Small distances produce severe perspective effects; large distances produce mild effects.
A perspective view remains in effect until the perspective effect is turned off or until a new view is defined in its place.
The following illustration shows the same model in both a parallel projection and perspective projection. Both are based on the same viewing direction.
To determine the point or angle in model space, you can
Viewing in 3D is available only in model space. If you are working in paper space, you cannot use 3D viewing commands such as VPOINT, DVIEW, or PLAN to define paper space views. The view in paper space is always a plan view.