Trees have earned a reputation among lighting artists for being difficult to light in an appealing way. A tree canopy is composed of a myriad of leaves facing random directions. Without shadows, standard diffuse lighting of a canopy yields unappealing visual noise. In Over the Hedge and Shrek III, we derive a set of aggregate normals that account for the shape of a leaf canopy. Combining this normal with the geometry normal of each leaf before shading yields a more appealing tree shape.

Research Paper for Simplified Tree Lighting Using Aggregate Normals