Abstract: An imaginary wall method is proposed to determine the visibility of line and plane intersection or plane and plane intersection. Three typical cases are discussed concerning the former topic: a line in the general position intersects with a plane in the special position, a line in the general position intersects with a plane in the general position, and a line in the special position intersects with a plane in the general position. Three typical cases are also discussed on the latter topic: the intersection of two planes both in the special position, a plane in the general position intersects with a plane in the special position, and the intersection of two planes both in the general position. The imaginary wall method can determine the visibility of line and plane intersection or plane and plane intersection quickly and accurately. This method can also provide some references for the learning and teaching in mechanical drawing courses.

Key words:  line, plane, intersection, visibility