## Principles of Linear Perspective with Mark and Mary Willenbrink

Both magicians and artists entertain with illusions. Magician use smoke, mirrors and other props. The artist must rely on a flat two-dimensional surface to imply an illusion of visual depth and convince the viewer that a scene is three dimensional. One of the ways visual depth can be expressed is through linear perspective.

The Railroad Bridge at Argenteuil by Claude Monet, 1873.

### Linear Perspective Basics

Linear perspective conveys depth through lines and the placement of forms. Though compositions can vary in complexity, the following tips and basic principles are inherent to all linear perspective drawings.

Horizon: The horizon is the line where the sky meets the land or water. The height of the horizon influences the placement of the vanishing points and the elevation of the scene.

Vanishing point: A vanishing point is the place where parallel lines appear to meet in the distance. In the example above, the parallel lines of the road recede or travel backward and visually merge to create a single vanishing point on the horizon. There is no limit to the number of vanishing points that a scene can have.

Ground plane: The ground plane is the horizontal surface below the horizon and may be land or water. In the example above, the ground plane is level. However, if the ground plane were sloped or hilly, the vanishing point–created by the path’s parallel lines–would not rest on the horizon and it might appear as if it were on an inclined plane.

Orthogonal lines: These are lines directed to a vanishing point, such as the parallel lines of the road shown above. Orthogonal means right angle. It refers to right angles that are formed by lines such as the corner of a cube shown in perspective.

Vantage Point: Not to be confused with vanishing point, the vantage point is the place from which a scene is viewed. The placement of the horizon and the vanishing points affects the vantage point.

### Perspective Principles

Four principles that characterize how depth is conveyed in linear perspective are size of forms, overlap of forms, placement of forms and convergence of lines. All four principles can and should be used together to best interpret perspective.

#### Size of Forms

The largest of similar forms will appear closest to the viewer. With this scene, the square on the right appears closest because it is largest of the three. The square on the left appears to be the farthest away because it is the smallest.

#### Overlap of Forms

The square at the top looks bigger because it is overlapping the square at the bottom.

#### Placement of Forms

Forms placed farthest from the horizon appear closest to the viewer. The square on the right is farther from the horizon than the other two boxes, causing it to look closer to the viewer, whereas the other boxes are closer to the horizon, making them appear farther away.

#### Convergence of Lines

Parallel lines converge in the distance. In this scene, the road lines (orthogonal lines) meet as they recede into the distance, giving the appearance of depth. A vanishing point is formed where the orthogonal lines meet. The principle of convergence of lines shares the concept of depth expressed through size in that the width of the path decreases with distance.

As you become more familiar with the basic principles of linear perspective, you may find that you are already applying them. You simply didn’t realize it. Utilizing the principles is sure to improve the accuracy of your drawings.