Two Point Perspective
Before getting into two point perspective, ensure you have at least read our first tutorial on What A "Vanishing Point" Really Is which contains new insights on the true nature of vanishing points—facts unbeknownst until recently.
Direction Points & Foreshortening
Below is a long box. Note that its front two sides are foreshortening away from us.
Also observe that two direction points are used here for two of the directions it is pointing away from us, giving us two point perspective.
Positioning the object closer to its direction point will foreshorten it more. In this case, the left side of our box foreshortens more than its front. This tells us that great distance is not necessary to make an object vanish. Being close to its direction point, visually, is enough. Rarely do objects extend very far anyway.
Direction points are used with foreshortening. After all, foreshortening is based upon an object's direction to us. So in spite of conventional wisdom, becoming smaller with distance is not something essential to the so-called "vanishing point."
Here is the same two point perspective scene but from overhead. (right) To find each direction point, all our viewpoint has to do is look in the distance in the same directions as the box. In fact, a direction point can even be thought of as our one matching direction seen from its end.
Direction Points & Our Viewpoint
We know from our last two point perspective illustration that a direction point can be found by looking into the distance in those same directions as the object.
Indeed, since the directions of our viewpoint and the object are basically the same at the direction point, there will literally be no difference between the direction point and our viewpoint of that object. For example, notice that each face of our box illustrated at the top of the page is angled to each direction point just as if each were our own position. In other words, with the direction point is on the left, we see that part of the object from the left.
Put another way, since the direction point represents an object's direction away from our viewpoint, (left pic) the angle this object has to its direction point is also the same basic angle it has to us. (right pic)
Direction points, therefore, establish our position in relation to objects by establishing our direction in relation to objects.
This applies whether one or two point perspective is used.
And so if we want to see a one point perspective box from an angle above it, just place its direction point above it. (right)
Still, our viewpoint and direction point are not the same things. Even though our directions are basically the same, a direction point represents that object's equal but opposite direction away from our viewpoint.
So it seems only natural that a "vanishing point" in one or two point perspective was not really associated with our viewpoint before since we are so opposite in this way. Direction points act like mirror reflections of our viewpoint for each of an object's different directions.