The space configuration illustrated in V?H?W three-plane projection drawing(i.e.front view

top view and left view) can generally be determined completely.However

in some special cases

the uncertainty of the space configuration illustrated in V?H?W three-plane projection drawing is neglected.This paper exemplified that it is very important to pay attention to the uncertainty of the space configuration illustrated in V?H?W three-plane projection drawing

and to avoid the variablility in the engineering design.