The aim is to help speed up the process of creating perspective grids and construction lines as a basis for a drawing using traditional materials. The grids and construction lines can be placed quickly and it doesn't matter if the vanishing points are far away from the page.
Note that vPoint is currently only supported on Chrome and Firefox
You start with a perfect square and draw diagonals fron opposite corners. This gives you the center point. And you draw the horizontal and vertical line through that center point, dividing the square into four equal squares, also giving you the first four points on the circle: