Drawing perspective is a method of portraying objects on a flat surface so that the dimensions shrink with distance. Each set of parallel, straight edges of any object, whether a building or a table, follows lines that eventually converge at a vanishing point. Typically this convergence point is somewhere along the horizon, as buildings are built level with the flat surface. When multiple structures are aligned with each other, such as buildings along a street, the horizontal tops and bottoms of the structures typically converge at a vanishing point. When both the fronts and sides of a building are drawn, then
Clifford parallel Clifford parallel In elliptic geometry, two lines are Clifford parallel or paratactic lines if the perpendicular distance between them is constant from point to point. The concept was first studied by William Kingdon Clifford in elliptic space. Since parallel lines have the property of equidistance, the term "parallel" was appropriated from Euclidean geometry, but in fact the "lines" of elliptic geometry are curves, and they have finite length, unlike the lines of Euclidean geometry. The algebra of quaternions provides a descriptive geometry of elliptic space in which Clifford parallelism is made explicit. The lines on 1 in elliptic space are