Lines converging to a single point give to the observer a sense of depth. This basic principle is used in perspective to simulate three dimensional worlds on two dimensional supports (i.e. canvas, sheet and so on). In this article I am going to introduce the one point perspective. It is applicable when one of side of the object to represent is parallel to the projection plane. In these conditions, all the lines converge towards the central focal point located on the skyline. In this example, I am going to show a cube in one point perspective.
Let’s start drawing the horizon line, vanishing points and the face of the cube, with vertices ABCD, parallel to the projection plane. The distance of the lateral vanishing points from the central vanishing point is equal to the distance of the observer from the projection plane.
Let converge all vertices towards the central vanishing point.
Now the question is: how deep the cube should be so that the segment XX, in perspective, is considered has the same length of the AB segment? I join the points A and B with lateral vanishing points. These lines join in E and F the perspective lines. Let’s trace a vertical line starting from E that touches perspective lines in C and G.
I combine the points obtained so far to get a perfect cube in one point perspective.
The central vanishing point, of course, is positioned in front of the observer. If he moves left or right, the central vanishing point automatically moves in this direction by altering the view of the cube. In Figure (a) the observer is moved to the right, so that side of the cube will be more visible. In figure (b) the observer is moved to the left thus making visible the left side of the cube. It ‘clear that the observer can move left or right to a certain point, beyond which the cube will be seen in two point perspective.