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Practical Drawing Series
Perspective (Part 3)
By Nick Ustinov
Let's look into some other linear perspective rules: - Parallel nature lines, for example rails, going into the depths seem to join in one point. They should be drawn directed to that point. If they are parallel to a drawing plane they will remain parallel on the picture. That's why vertical lines are always drawn vertical. An exception could be a case when the drawing plane is assumed to be inclined: in that case verticals would join.
- If lines are parallel to a horizon plane or an object plane, the joining point lies on the horizon line. If they are inclined, then the joining point is located below or above the horizon line.
- Straight lines, perpendicular to a drawing plane on the picture, will join in the central joining point.
As you can see here, cubes are arranged at different heights in frontal alignment. All vertical edges (and half of the horizontal edges) are parallel to a drawing plane. All other horizontal edges are perpendicular to a drawing plane and are pointed to the central joining point. 
Here you see the cubes, arranged at a random angle to the drawing plane. Cube a is aligned at 45 degree angle, so that's why edge projection to different sides is the same for it, but the joining points at the left and right are located at the same distance from point p (this distance is assumed to be equal to the distance between a view point and point p). Farthest and closest edges of the cube are located on the same vertical. Cubes d and e are situated in the same horizontal plane with random angles to the drawing plane. This means that there's one group of vertical edges and two groups of parallel horizontal edges, that have common joining edges on horizon line. Cube c is aligned so four edges are horizontal and one of them is located in the horizon plane. This means these edges will have a common joining point at a horizon, in our case outside the drawing. Cube b has all edges inclined, so all three joining points are located above the horizon.
[ Click here to move to the last part of this article ]
This article first appeared in November, 1998.
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