THE DEFINATION OF PERSPECTIVE IN DRAWING

Imagine driving along a very straight open road on a grassy plain. The road, the fences, and the power-poles all diminish toward a single point far ahead of you. That's single-point perspective.

Single- or one-point perspective is the simplest method of making objects look three-dimensional. It is often used for interior views or trompe l'oeil (fool the eye) effects. Objects must be placed so that the front sides are parallel to the picture plane, with the side edges receding toward a single point.

A perfect example is Da Vinci's "Adoration of the Magi." The building in the background faces the viewer, and the stairs and the side walls get smaller as they move toward a single point in the center of the painting.

When we talk about perspective drawing, we usually mean linear perspective. Linear perspective is a geometric method of representing the apparent diminishment of scale as the distance between an object and the viewer increases. Each set of horizontal lines has its own vanishing point. For simplicity, artists usually focus on correctly rendering one, two, or three vanishing points.

The invention of linear perspective in art is generally attributed to the Florentine architect Brunelleschi. His ideas continued to be developed and used by Renaissance artists, notably Piero Della Francesca and Andrea Mantegna. The first book to include a treatise on perspective, "On Painting," was published by Leon Battista Alberti in 1436.

In one-point perspective, the vertical lines that run across the field of view remain parallel, as their vanishing points are at "infinity." The horizontal lines, however, which are perpendicular to the viewer, vanish toward a single point at the center of the image.

If you are experimenting with perspective, you can practice one-point perspective by doing this:

• Draw a straight line across the middle of your drawing. This is your horizon line. Locate a point along this line—it may be in the center, though it does not have to be—and mark it. This is your vanishing point.
• Draw the facade of a simple building to the right of the vanishing point.
• Using a ruler, draw a soft line from the top-left corner of the building to the vanishing point. Then draw another line from the bottom-left corner to the vanishing point. These lines show how the building will get smaller as it gets farther away from the viewer.
• Locate the end of the building somewhere along the lines you have just sketched. Mark it by drawing a line parallel to the building's facade. Erase the remaining line segments that connect to the vanishing point.
• Using the same method, add other buildings to the drawing.

In two-point perspective, the viewer is positioned so that the objects in the drawing or painting are viewed from one corner. This creates two sets of horizontals which diminish toward vanishing points at the outer edges of the picture plane, leaving only verticals perpendicular.

It is slightly more complex, as both the front and back edges and the side edges of an object must diminish toward vanishing points. Two-point perspective is often used when drawing buildings in landscapes.

Two-point perspective uses the same method described above. The main difference is that the viewer is looking from one corner rather than head-on. For this reason, you cannot begin the drawing with the building's facade. You must first draw the line that forms the corner of the building, then use one of the vanishing points to complete the facade.

In three-point perspective, the viewer is looking up or down so that the verticals also converge on a vanishing point at the top or bottom of the image. This is the most complex form of perspective. Unlike in one-point and two-point perspective, none of the lines in the drawing are perpendicular to the viewer. Instead, each one is drawn in the direction of a certain vanishing point. If you were drawing a building using three-point perspective, you would need to begin with only a single point located on the building, then use the vanishing points to define each side of the structure.