Linear perspective is a critical element when painting buildings and other objects with distinct lines. The nearer to the forground the structures are, the more critical it is to have good linear perspective. I suspect that this is a somewhat complex subject when treated rigorously, such as by an architectural illustrator. However, an artist needs to understand only some fundamentals in order to use linear perspective effectively.

While there are many sources available, in print, as well as on the Internet, I had two simple questions for which I was unable to find answers, so I took upon myself to find the answers. I share them here with the hope that others may also benefit.

I will begin with the basics since a sound understanding of fundamentals is critical to the mastery of any topic. Developing these fundamentals leads to the answers to my two questions, which pertain to the shape of a roof and the location of the centeline in a vertical plane.

The two basic elements upon which linear perspective is based are the "Horizon Line" and "Vanishing Points".

The Horizon Line is the line of view when an observer is looking "straight out". The observer's view is parallel to the surface of the earth at the observer's position.

In this example, the Horizon Line is between the top and bottom of the posts. The line at the top of the posts is actually parallel to the line where the posts meet the ground (when not viewed at an angle). Note that the line at the top of the posts, above the horizon line, slopes down to the right of the observer and slopes down to the left of the observer. Conversely, the lines where the posts meet the ground slope up. These lines intersect the Horizon Line at common points that are referred to as Vanishing Points (v.p.). Notice that the spacing between the posts decreases to the right and left as we move away from the viewer. We will discuss the implications of this below.

Finally, look at the front-of-porch plane in the above figure, and notice the location of the centerline, which is the actual center of the plane when viewed straight from the front. The centerline is off the center of the plane when it is viewed from an angle. The greater the angle, the more the centerline moves to the right or to the left depending upon whether the object is viewed from the right or the left. This is the same spacing effect we discussed before, where the fence posts in are closer together the further you move either to the right or left, away from the observation point. I think that this spacing is intuitive when, for instance, drawing a line of fence posts. However, it may not be so intuitive when just considering the centerline of the front of a building.

These two details, the shape of the roof and the location of the centerline in a vertical plane, are both important to achieving good linear perspective, especially in buildings that are in the middle and foreground of a picture. However, learning how to draw these was a challenge for me so I've discussed them here to help others who may have the same challenge.

Footnotes:

1. The architectual illustration, Plan No. JVA-2406, is provided by the courtesy and permission of Jannis Vann and Assoc., Inc. of Woodstock, GA

2. " Vertical Vanishing Point" may not be the generally accepted term for this point.