Platformer - iPhone Game Blueprints - page 198

strated the spectacular advantages of such system was The Old Mill produced by
Disney in 1937. The method was immortalized in the same year when Snow White
and the Seven Dwarfs released.
The following image shows a parallax layout of a game scene:
2D games use the same approach to create the illusion of depth. Of course, they
have no cabinet for layers, but the landscape is fully constructed of flat images,
which have specific rules to determine their speed. One of the early examples of
scrolling parallax can be found in the game Jump Bug published by Rock-Ola in
1981. It featured a solid main scene that scrolls, a fixed night sky with some stars,
and slowly moving clouds. This can be read as an attempt to illustrate the depth of a
virtual scenery. A year later, the game Moon Patrol was developed by Irem , in which
the scrolling parallax was implemented in full form. The game had three moving lay-
ers that vividly simulated the distance between them.
Commonly, the scrolling parallax in games is calculated by eye, without any concep-
tual formulas, because nobody knows the exact z position of objects in the back-
ground, allowing them to have any given speed (that is, in a case it looks persuasive
enough). There is only one general rule: counting from the main scene, each next
layer should be slower than the previous one. For instance, you give the main scene
speed that is equal to a variable called v , the next layer should be v x 0.4 , followed
by v x 0.2 , and so on. Your own taste forms the picture.
The following figure shows the calculation of a scrolling parallax: