Vanishing point as the "direction point", as lines having the same directional vector, say "D", will have the same vanishing point. Mathematically, let be a point lying on the image plane, where is the focal length (of the camera associated with the image), and let be the unit vector associated with , where . If we consider a straight line in space with the unit vector and its vanishing point , the unit vector associated with is equal to , assuming both are assumed to point towards the image plane. When the image plane is parallel to two world-coordinate axes, lines parallel
Point-to-point construction designed operating procedures. An intermediate form of point-to-point construction uses terminal strips (sometimes called "tag boards") or turret boards. The crucial invention was to apply soldering to electrical assembly. In soldering, an alloy of tin and lead, or later bismuth and tin, is melted and adheres to other, nonmolten metals, such as copper or tinned steel. Solder makes a strong electrical and mechanical connection. Note that if components are arranged on boards with tags or turrets at both ends and wires going to the next components, then the construction is correctly called tag or turret construction respectively, as the components