by Janet Glatz
Perspective is a complicated subject for artists; when a structure is sitting in an oblique position toward the viewer, it really gets interesting, as in this old beauty.
So I'm going to break it down step by step. First I'll tell you what I'm going to do and why, and then add a photo beneath it. So here goes:
The next step is to draw the corner of the object. Most commonly, two point perspective is used for drawing buildings or interiors, so this line could be the corner of a building. This line is drawn in between the two vanishing points and can cross over the horizon line. Note: the height of the corner determines the size of the structure.
Receding lines are next drawn from each end of the verticle corner line to each one of the vanishing points. These lines are called orthogonal lines. Any additional set of lines (say for the peaked roof) that recedes away from the viewer will follow along these lines to one of the vanishing points.
Parallel, vertical lines are drawn to indicate the other two visible corners.
When a form is placed so that it overlaps the horizon, no additional lines are needed to define the overall form of the object. However, when the form sits high or low in your scene, new rules apply.
Below the Horizon Line (using the same two vanishing points and horizon)
For forms placed below the horizon line, the steps remain the same. However, the top of the form will be visible. This means that the top portion of the form will be defined by the orthogonal lines that extend from each corner back to the opposite vanishing point.
It is important to note that the locations of where these lines intersect define the back corner of the cube.
Above the Horizon Line
For forms placed above the horizon line, the same steps are followed. In this case, the bottom portion of the form is now visible to the viewer. The bottom portion is defined by extending lines from each end of the cube to the opposite vanishing point.
As is the case with the other examples, additional lines exist but are not visible in the finished drawing. (the part of the lines that extend beyond the object/building.) When complete, all lines that are no longer needed can be erased revealing the illusion of 3D forms in space.
Adding Additional Details
Additional details can be added to a scene to create limitless possibilities. Vertical lines are drawn to indicate edges and corners, while orthogonal lines are drawn (using the lines of the buildings as guides) for parallel edges that recede into space. Every line that runs to the vanishing point must follow the same trajectory as the building lines do. Note that if you place a straight edge on the top line of the last tall building, it alligns with the vanishing point, as to the tops of all the buildings.
This skill takes practice. I once complimented an artist who was displaying gorgeous and perfectly formed perspective paintings of city streets. When I told him how good they were, he said with a straight face, "They should be, I've been teaching perspective for 30 years."
For more about and by Janet Glatz, visit www.janetglatz.com