Tree Textures. Modern techniques in art historical context

We investigated tree textures starting from art historical sources describing the complicated appearance of trees, proceeding with an empirical survey using computer vision techniques, concluding with an overview of physical factors. Our main question was: Which perceptual, image statistical and optical phenomena primarily determine the appearance of trees and how are these phenomena related? The interdisciplinary approach exemplies how art theoretical writings can be employed to investigate object appearance. We found that bark textures generally obey models for opaque rough materials. For foliage, we found image correlates for the four main qualities which were listed by Leonardo da Vinci already: light, shadow, luster and translucency. Although these qualities are clearly present in the images, and can be recognized visually, only luster could be computed with conventional physics based computer vision techniques. We conclude that there is a need for a texture model of foliage which takes into account the anisotropic, open structure of foliage as a whole.