Vanishing point is the point in perspective where all lines in space intersect. It is located on the circle of intersection, between light body and surface, and is 360° around the observer. Picture above depicts an observer, his circle of sight, and the vanishing points depending on his view direction.
We're already familiar with the horizon line, and with the interaction of light bodies from the previous titles. In order to describe the mechanics behind the vanishing point, we need to add a “tendency line” to the already described principles of interaction between light bodies.
The tendency line is a straight path which determines the moving direction of the object. Picture above shows an object, which is higher than the observer, approaching and receding from left to right along the tendency line. The red connection points mark the points at which the blue object appears on the horizon. The blue object appears at the point where the circles first intersect; and disappears at the point where the circles disconnect. The red dots represent the two vanishing points.
We can apply the principle of intersection in many ways (Picture above). The two red dots represent the vanishing points in this case.