Loci of Points & Orthographic Projections topics include: Loci points, bis code, orthographic projections basics and problems, first and third angle projection method.

The locus of a point is the low side of the point for the end of a link. 

Orthographic projection is a way to represent 3D objects in 2D. It's a type of parallel projection where all the projection lines are perpendicular to the projection plane. The result is that every plane of the scene appears in affine transformation on the viewing surface.