Patterns projected from lighting instruments, such as the shape of light streaming through windows or the shadows cast by branches and leaves, are generally created by objects commonly referred to as "gobos." This is short for "go-between" because the pattern, generally made of cut steel or tempered glass, is placed between the lamp and the lens within the lighting instrument. These projected patterns are used in film to create the look of light through windows or blinds, light passing through trees, or sometimes used in soft focus to simply break up the light and add texture to a scene. In theater, they are also often used to project background images such as cityscapes, and in dance and music performances they may be used to project abstract patterns onto the performers.
Motorized rotators are often combined with gobos to create a variety of effects. In addition to simple rotating effects such as spinning spirals or other shapes, two gobos may be used to create the look of motion, such as placing a pattern of leaf shadows in a stationary gobo holder, then adding a soft-focused pattern of abstract shapes behind it. When the soft-focused pattern spins, it causes shadows to hit various parts of the leaf gobo, creating the illusion of leaves moving on the wind. Similar techniques may be used to create the illusion of moving reflections off water or the flickering light of a fire, depending on the colors and patterns used. Dual rotators that spin two patterns in opposite directions are also available and can be used for similar effects.
Unlike rotating pattern lighting effects, scrolling effects can create the illusion of continuous motion in the light. Often used to project the illusion of falling rain or passing clouds on a theater backdrop, scrolling patterns use a thin loop of cut steel. They also are used to create the illusion of swiftly passing scenery in film, such as in a scene that takes place inside a moving train car. The pattern cut into the steel is generally soft-focused and attached to a scrolling unit that continuously feeds the loop in a circle, sort of like the belt on a treadmill. When the light passes through the pattern as it crosses itself going both directions, the illusion of motion in the light is created.