Pseudo-3D
From Wikipedia, the free encyclopedia
Pseudo-3D is a term that means that a computer system, usually a video game, uses 2D computer graphics to visually simulate 3D computer graphics. While a 2D game usually allows movement only vertically and horizontally, a pseudo-3D game most often gives depth as a third dimension of acting. For its intermediate step between 2D and 3D both graphically and historically, pseudo-3D sometimes also is named 2.5D computer graphics. It was a big step in gaming history from abstract graphics towards realistic graphics. The passage to texture mapping is fluent. Technically all graphics displayed on a screen are 2D, which makes Pseudo-3D impossible to concisely define. For example, '3D' games such as Quake are subject to gimbal lock which imposes certain movement constraints on the player, despite the common perception of a true 3D environment.
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[edit] Examples
1986's Out Run is a good example for a classic pseudo-3D racing games. As one can see in the given picture, the player has to drive his Ferrari in the depth of the game window. The palms on the left and right side of the street are basically the same bitmap, but have been scaled to different sizes, creating the illusion that some are closer than others (this technique is also used in more recent games, such as Far Cry, to create the illusion of dense foliage). The angles of movement are left and right and into the depth (while still capable of doing so technically, this game didn't allow to make a U-turn or go into reverse, therefore moving out of the depth, as this did not make sense to the high-speed game play and tense time limit). Notice the view is comparable to that which you would have in reality when driving a car. The position and size of any billboard is generated by a (complete 3d) perspective transformation as are the vertices of the poly-line representing the center of the street. Often the center of the street is stored as a spline and sampled in a way that on straight streets every sampling point corresponds to one scan-line on the screen. Hills and curves lead to multiple points on one line and one has to be chosen. Or one line is without any point and has to be interpolated lineary from the adjacent lines. Very memory intensive billboards are used in OutRun to draw corn-fields and water waves which are wider than the screen even at the largest viewing distance and also in Test Drive to draw trees and cliffs.
Compared to 1980's Rally-X, you see that this game uses an abstract viewing angle to show a racing field.
Sonic the Hedgehog for the Sega Mega Drive uses parallax scrolling for aesthetic reasons. Parallax scrolling can be considered a form of pseudo-3D, as it uses 2D graphics that moves corresponding to the rules of three dimensional geometry.
The Street Fighter II games used parallax scrolling on the ground of each stage, for a good pseudo-3D effect.
The same effect was used in the first Real time strategy game to use pseudo-3D or 3D graphics, Stronghold (1993). The game was described as Dungeons and Dragons meets SimCity and displayed a pseudo-3D city with different structures built by humans, dwarves, elves etc. spread across a hilly terrain.
[edit] History
The first computer games that used pseudo-3D were arcade games, led by Pole Position by Namco (1982), which pioneered the trailing camera racing game that is now so familiar in true 3D games. The same effect, however, was first used with vector graphics in Speed Freak in 1979.
The first home video game to use pseudo-3D, and also the first to use multiple camera angles mirrored on television sports broadcasts, was Intellivision World Series Baseball (1983) by Don Daglow and Eddie Dombrower, published by Mattel. Its television sports style of display was later adopted by 3D sports games and is now used by virtually all major team sports titles.
As this era of gaming opened, there was a strong need for games that added believed new game play and intensive, cool visual effects. After Pole Position, Space Harrier, After Burner II, Out Run, and Hang On are among the most popular arcade games of that time.
The first game to use pseudo-3D to create optical; illusions for play may be Realm of Impossibility by Mike Edwards, which was published by EA in 1984.
With the advent of computer systems that were able to handle several thousands of polygons (the most basic element of 3D computer graphics) per second and the usage of 3D specialized graphics processing unit, pseudo 3D became obsolete. But even today, there are computer systems in production, such as cellphones, which are not powerful enough to display true 3D graphics, and therefore use pseudo-3D for that purpose. Interestingly, many games from the 1980s' pseudo-3D arcade era and 16-bit console era are ported to these systems, giving the manufactures the possibility to earn revenues from games that are now nearly twenty years old.
[edit] Technical aspects
The reason for using pseudo-3D instead of "real" 3D computer graphics is that the system that has to simulate a three dimensional looking graphic is not powerful enough to handle the calculation intensive routines of 3D computer graphics, yet is capable of using tricks of modifying 2D graphics like bitmap. One of these tricks is to stretch a bitmap more and more, therefore making it larger with each step, as to give the effect of an object coming closer and closer towards the player.
[edit] Generalization
Even simple shading and size of the image could be considered pseudo-3D. This is because shading makes it look more realistic, and if the light in a 2d game were 2d, it would only be visible on the outline, and outlines are often dark, and you would not be able to see it well. Although, if there was visible shading, then that would mean that it was pseudo 3d lighting, and therefore a type of pseudo 3d. Changing the size of an image can cause the image to appear to be moving closer or further away, which could be considered simulating a third dimension.
