sorry the notation is bad but given image I here, and line AB,CD,or EFG or just name any one line in the image

how to infer their length, position, angle, direction, curvature, so that the line DRAWN will represent a "proportionate" image of said 3d object? in a way so AB is correct against CD and against EFG and vice versa, thus representing I based on object O

so far i only know by using projection matrix against the object's xyz position to gain its screen coordinate, which means notating its entire polygon/NURBS coordinates, but i could be wrong and they maybe so please share as much as you know(and maybe also the aplication.