Too often when we are painting outside, or from a photographic reference we are dead set on painting what we see, which can be very frustrating because it's impossible to recreate our natural surroundings with a few colors on a flat surface. But we can suggest what the light is doing in
terms of value and temperature. The same holds true for our composition, when we see straight horizontal or straight vertical lines we need to suggest what would work better.
Straight lines are static and can cut the composition off where angled or curved lines can lead the viewer into the picture. The first painting by Willard Metcalf has angled or curved lines that flow through out the painting. It's impossible to know if these artists painted exactly what they saw or had to modify the lines but the compositions work and have no straight, static lines. To the
left is a painting by Ernest Blumenschein. There isn't a straight line in the painting. The lines of the river bank draw you into the painting and the angled lines of the mountain and trees keep the painting from being static.
The last painting by Aldro Hibbard also has flowing lines in the river that lead you into the painting. The lines of the houses and mountains flow through the painting nicely. Even the straight trees aren't straight, they are slightly angled or curved.