A few weeks ago I had the opportunity to participate in a plein air event to paint an old house in Madison Georgia. Only 3 artists showed up which was a sad thing. It was not going to be a simple or easy undertaking as the house was in bad shape. Lots of boards brought in and put in place to help support the old house in various places. All in all, it wasnt that bad. Just confusing because the house wasnt fully in tact . So my goal was to try and paint it like it might've looked many years ago. I did my rough in of it in about 2 hours. A very very rough in. The roof angles were very demanding as there were sometimes only very slight variations in angles of many adjoining sections. After hit and miss quite a few times, I finally got the angles close to what they actually were. That mad all the difference. Once I got all the roof angles drawn correctly I saw hope for a painting. As long as those angles were off, the drawing/painting would never read right. Now there are times when its fine to be slightly off. It can add to interest to a painting. Its done all the time. But this was to be a painting representing what was once a beautiful large two story house that was 100 years old or more. Also there's a good possibility the painting it may be purchased by the Madison Historical Society. So the painting has to be representative.
In a recent workshop I instructed, I spent a lot of time with quite a few artists working on barns, sheds, etc. that they were painting. The primary issue was roof angles, apex, and also vertical length of sides. These angles are easy to draw incorrectly but difficult to draw correctly. I personally took a workshop with a very well known and great artist whose name I wont mention but this artist tried to assist me in drawing this roof angle on a barn that was not the norm. The artists worked on it back and forth. Long story short, after 10-15 minutes the artist literally gave up on it saying more time was needed to get it right than was available since there were 25 students at this plein air workshop. So there you go. even one of the very best had a problem with roof angles.
You have to seriously concentrate and study the angle to the angle you're viewing in real life. Whether it be plein air or in the studio there are things that can help you draw the right angle. Once you use these techniques enough times you learn what needs to happen and after a good while of practice and study, you wont need these tools to accomplish good angles.
One tool you can use is a caliper. You set it over the angle you're trying to draw then use that angle on your canvas or sketch pad. On the apex of a barn or building you open the caliper until it matches the apex angle. There you have it, It does'nt matter how large or small the photo is or how far or close you are to the structure. The angle does'nt change. You can also set one arm of the caliper along side the photo and move the other arm to find the angle of a roof or building line by its relation to the vertical side, top, or bottom of the photo. When outdoors you have to guess at the vertical arm position. Its tricky but working with it surely helps in getting you to draw more accurate structures.
Another thing you can do is place your sketch pad or canvas directly in line with the photo or outdoor structure you want to draw. Then draw the line as you think you see it on your sketch pad or canvas. Then hold a pencil in your hand and steady it on the structure line you want to draw. Keep your hand stiff and steady and lower it to your sketch pad or canvas. Compare the pencil position with the line you drew. Here you will see how far off you are or how close you are.
Yes, many successful artists don't paint angles correctly. This is usually a choice they make but they do know how to do do it. They choose not to for artistic reasons. You often see slanted buildings that don't really slant. Its said that a straight line is the most boring thing in art. So sometimes sloping a line adds interest.
As the artist, you have to decide how correctly a structure line has to be in order for it to read correctly or at least close enough to pass. Then you of course have you more abstract structure paintings where anything goes.