To determine the middle of a plane turned in space, such as the wall of a house to position a door or window in the middle, or to find the middle of an end wall to position the roof, draw diagonals in the rectangle that represents the wall or plane. This works whether the plane is facing straight at you or at any angle, and whether it is above, at, or below eye level.
As in the figure below, a line drawn through the crossed diagonals and parallel to the verticals will be in the middle. You can measure along the front of the plane to establish the middle, and draw a line from that point through the crossed diagonals to the middle of the other side.
Diagonals drawn through a plane vanishing in space establish the center of the plane.
Some more points to consider:
You can divide a plane as many times as you want by drawing successive sets of diagonals.
You can fit the curve of an arch into the rectangle after you have centered it. It's an easier way to draw it. You can draw a dock or bridge and get all the piers correctly placed by using diagonals to evenly break up the space.
You can divide a plane that is tilted in space, such as a roof, to determine the middle, for placing the chimney or a dormer correctly.
In a complicated street scene viewed straight across, such as the one below, most of the planes can be facing square on. At the edges of your vision, however, things will start to vanish to points at either side of the horizon or eye level, or to a center vanishing point.
In a complicated scene viewed at an angle, like the one following, the various planes of houses, walls, fences, and smaller items like cars, trucks, and even bikes, bridges, gates, or phone booths will be receding or vanishing to the two vanishing points at either side of eye level.
Was this article helpful?