Everyone is familiar with the way a railway line disappears to a point as it reaches the horizon. The same principle applies to absolutely everything in your drawing and while the rules themselves are relatively simple, they are not always obviously so.
The horizon is the key to perspective. It denotes the limit of what you can see at ground level and it indicates the viewer's height in relation to what can be seen. Anything above or taller than the viewer is above the horizon, anything shorter or below the viewer is below the horizon. Vanishing points will also generally be on this line.
As objects become further away from the viewer, they appear smaller. Lines that are parallel, horizontal and straight will eventually meet and vanish at a point on the horizon. This applies to lines of objects such as telegraph poles too.
In simple cases, such as the drawing above, all the objects run parallel to each other. Even the tops and bottoms of the telegraph poles form a straight line. All these lines meet at the same vanishing point on the horizon. When drawing something like this, it is often helpful to draw the lines in faintly, then erase them when details such as the poles have been drawn in.
Real life objects such as houses become more complicated because they obey several vanishing points. Each wall of the house will have its own vanishing point and everything on that wall, including doors, windows and window sills, will vanish at the same point if a continuous line is drawn from it. In the drawing above, there are two obvious vanishing points, but a further point can be found from the lines on the eaves of the roof; this vanishing point will be in the sky because the roof slopes upwards. Notice where the horizon passes through the doors and windows, just where you would draw the face of a person standing there.
© Adrian James 2001