Wednesday, May 7, 2014

Perspective - One Point Perspective - Distortions & Complications

Distortion is the principal cause of sorrow in hand layouts. A simple mistake at the initial marking of horizon and vanishing points can cause havoc in the final product. The following examples apply to both the cube examples of the previous posts, and to any layout, whether by hand or computer. It is a mixed bag of tips, so forgive the lack of order.

When creating a simple perspective using one point and a diagonal vanishing point, don’t stray far from the central point. The three cubes on the right are about as far from the central vanishing point as they can be. The cubes on the left are too far, and show some (or a lot of) distortion. Generally I try to stay within a circle whose center is the one point vanishing point, and whose radius is half way to the diagonal vanishing point.

In hand layouts or computer rendering, the closer your eye is to the object the more it will be like a wide-angle lens (see the plan and perspective on the right above). Distortion will start to occur at the edges the closer you get. Moving your eye away from the object will create a telephoto effect, flattening object (see the plan and perspective in the center above). You may need to get closer or further to see what you need to see, but keep in mind that this changes the aspect of the project.

The diagram above shows the distortion in both an exterior and an interior perspective when the eye is too close to the object or space; the object looks too long, and the space looks too deep.

This plan and layout shows that the distortion of the main room is acceptable, but the smaller room on the left is noticeably wrong. 

So much for distortion. The final illustrations involve complications in layout. They are more for fun, but are good to keep in mind as you think about perspectives. 

Here I’m taking the previous view of a large and small space, and showing how to make the large space into an octagon by slicing off the corners. The diagonal vanishing points are not very widely spaced, and so distortion is showing up.

If you have a plan that is rectangular you can use a diagonal “cross” to transfer the orthogonal plan onto a perspective shape. The green lines set up the transfer by directly moving lines to the perspective. In addition the green lines mark both the plan and the perspective with a diagonal “X”. The orange lines transfer all other lines to the perspective. Again, I’m not suggesting that it is the way to create a “perspectivized” plan since the computer does it in no time. But, it is something that is worth keeping in mind as you use the computer.

The illustration above shows that the grid can be used for the most non-rectilinear plan imaginable.

The photos above illustrate the perspective nature of stairs, ramps and escalators. If oriented the same way, they all will recede to vanishing points above or below the building’s vanishing point that is on the horizon.

The diagram and photo above address reflections in water in a perspective. Since water is generally below the ground level of a building, you have to plot the water’s level, and then mirror the building’s reflection from that point. Again, you will easily do this in the computer, but knowing what is going on keeps mistakes from happening.

Finally, a trick that computers can’t emulate. When drawing a perspective of a very small space like an elevator cab, you will find that the ceiling and floor will always look distorted. The easy answer to this problem is to create a “sliding” vanishing point. Instead of having a single vanishing point, use one vanishing point for the left wall (shifted toward the right), and another vanishing point for the right wall (shifted toward the left). The result is an elevator cab where the paneling joints look correct, but the vanishing points are actually shifting up (near the ceiling), and down (near the floor).

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