A Cucoloris (“cookie”) is used to create shadow patterns on backgrounds or subjects. A flatly lit wall can be broken up into textured pools of light and shadow to either simulate realism or craft a stylized environment. Lighting directors frequently use them to imitate sunlight filtering through trees.
There are several different types of cookies, each providing different effects, and the resulting pattern itself depends on the distance of the cookie to both the light source and the background.