träallax

träallax is a term that describes a visual effect where foreground objects appear to move faster than background objects when a viewer changes their position relative to the scene. This phenomenon is a direct consequence of perspective. The closer an object is to the viewer, the more its apparent position shifts against a more distant background as the viewer moves. This effect is commonly observed in everyday life, such as when looking out of a moving vehicle's window. Trees and fences close by seem to rush past, while mountains or the horizon appear to move much more slowly or not at all.

The principle ofträallax is widely used in various media to create a sense of depth and immersion. In video games, it is employed to make the game world feel more three-dimensional, particularly in 2D side-scrolling games where layers of background art move at different speeds. This creates a parallax scrolling effect. Similarly, in traditional animation and film, layered backgrounds are moved at varying rates to simulate depth without resorting to complex 3D rendering. The term itself is a portmanteau, combining "parallax" with "trä," a Swedish word for "tree," likely referencing the common observation of trees moving at different speeds. While not a strictly scientific term, it is understood within certain creative and technical communities to describe this specific visual illusion.