Art is an Expression of the Soul
Vertical Vanishing Point and the Shape of the Roof.
Now, let's look at what happens if the fence posts we looked at earlier are not
perfectly vertical but are tipped over, much like a fence that has seen a good many years of service. This is illustrated in Figure
4, where by a strange coincidence, all the posts lean over, away from the viewer, at the same angle. Notice how another vanishing
point comes into play: the Vertical Vanishing Point (v.v.p.).(2) Notice, also, the plane depicted in blue, which is the general
shape of the roof of a house, as discussed next.
Next, look at Figure 5 and notice how the Vertical Vanishing Points comes
into play in determining the shape of the roof. The left and right edges are like the posts in figure 4 and the top and top and bottom
are horizontal lines that converge at the right Vanishing Point. The general shape of the blue planes in figures 4 and 5, differ only
because in Figure 5 the Horizon Line has been moved down so that it is similar to where it would be for an observer on the ground.
help draw the roof, look at Figure 6, and notice that the line at the front of the roof, L3, is longer than the line at the peak,
L4. Also, the slope at the right edge of the roof is less steep than the slope at the left edge. In other words, the roof flattens
out as we move away from the viewer. Detemining the exact slope of each edge and the top and bottom of the roof requires the knowledge
and techniques of the architectural illustrator. Fortunately, artists can usually determine this for our purposes by using by a little
trial and error and the guidelines noted here. (I always sketch buildings and make sure that I am satisfied with the perspective before
I draw them on the canvas and begin painting.)
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. This is llustrated by Figure 1.
Using Horizontal Lines and Vanishing Points in Paintings.
Now let's see how the Horizon Line and Vanishing Points relate to the
horizontal lines in a structure. Figure 3 depicts a home, as it would appear to an observer standing in front of and to the left of
the structure.(1) Notice how the lines representing the front and top of the roof and the lines along the porch rail converge
at the right Vanishing Point. This is true as well for other horizontal lines on the front of the home, such as the lines in the siding
and the lines representing the top and bottom of the windows, as well as the dividers in the window panes. Likewise, horizontal
lines on the left side of the house converge at the left Vanishing Point. (Here, the term "horizontal" refers to lines that are parallel
to the horizon line when not viewed at an angle.)
1. The architectual illustration, Plan No. JVA-2406, is provided by the courtesy and permission of Jannis Vann and Assoc.,
Inc. of Woodstock, GA
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.
1. The architectual illustration, Plan No. JVA-2406, is provided by the courtesy and permission of
Jannis Vann and Assoc., Inc. of Woodstock, GA
1. The architectual illustration, Plan No. JVA-2406, is provided by the courtesy
and permission of Jannis Vann and Assoc., Inc. of Woodstock, GA
Vanishing Points. Consider parallel lines in a plane that is perpendicular to an observer's line of sight. This is illustrated
in Figure 2, where the blue "X" represents the position of the observer. The vertical lines could be fence posts that are the
same height installed on "flat" ground.
The Basic Elements of Linear Perspective
Centerline in Vertical Planes
Finally, look at the front-of-porch plane in Figure 6, 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 Figure 2 are closer
together the further you move either to the right or left, away from the observation point. I think that this spacing effect 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.
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.