One of the first questions to ask yourself is how many spatial dimensions your physical space will have. It is essential to understand that the dimensionality of the game’s physical space is not the same as how the game displays that space (the camera model) or how it implements the space in the software. How to implement the space and how to display it are separate but related questions. The former has to do with technical design, and the latter has to do with user interface design.
Ultimately, all spaces must be displayed on the two-dimensional surface of the monitor screen.
These are the typical dimensionalities found in video games:
■ 2D. A few years ago, the vast majority of games had only two dimensions. This was especially noticeable in 2D side-scrolling games such as Super Mario Bros. (see Figure 4.1). Mario could run left and right and jump up and down, but he could not move toward the player (out of the screen) or away from him (into the screen).
Two-dimensional worlds have one huge advantage when you’re thinking about how to display them: The two dimensions of the world directly correspond to the two dimensions of the monitor screen, so you don’t have to worry about conveying a sense of depth to the player. On the other hand, a number of games with 2D game worlds still use 3D hardware accelerators for display so that objects appear three-dimensional even though the gameplay does not use the third dimension.
Two-dimensional worlds may seem rather old-fashioned nowadays, but there are still many uses for them in casual browser-based games and smaller devices such as low-end mobile phones.
ptg7947181 GAME WORLDS 87
C H A P T E R 4
■ 2.5D, typically pronounced “two-and-a-half D.” This refers to game worlds that appear to be a three-dimensional space but in reality consist of a series of 2D layers, one above the other. StarCraft, a war game, shows plateaus and lowlands, as well as aircraft that pass over obstacles and ground units. The player can place objects and move them horizontally within a layer with a fine degree of precision, but vertically an object must be in one plane or another; there is no in-between. Flying objects can’t move up and down in the air; they’re simply in the air layer as Figure 4.2 depicts.
FIGURE 4.2 StarCraft, with plateaus and lowlands visible FIGURE 4.1
Super Mario Bros., the classic 2D side- scrolling game
ptg7947181
■ 3D. Three true dimensions. Thanks to 3D hardware accelerators and modeling tools, 3D spaces are now easy to implement on hardware that supports them. They give the player a much greater sense of being inside a space (building, cave, space- craft, or whatever) than 2D spaces ever can. With a 2D world, the player feels as if he is looking at it; with a 3D world, he feels as if he is in it. 3D worlds are great for avatar-based games with exploration challenges, such as the Prince of Persia series (see Figure 4.3). Most large games for personal computers and consoles now use three dimensions, but many small casual games still need only two.
■ 4D. If you want to include a fourth dimension for some reason (not counting time), implement it as an alternate version of the 3D game world rather than an actual four-dimensional space. In other words, create two (or more) three- dimensional spaces that look similar but offer different experiences as the avatar moves among them. For example, the Legacy of Kain series presents two versions of the same 3D world, the spectral realm and the material realm, with different gameplay modes for each. The landscape is the same in both, but the material realm is lit by white light while the spectral realm is lit by blue light, and the archi- tecture is distorted in the spiritual realm (see Figure 4.4). The actions available to the player are different in each realm. The realms look similar but are functionally different places governed by different laws. In the movie version of The Lord of the Rings, the world that Frodo inhabits while he is wearing the Ring can be thought of as an alternate plane of reality as well, overlapping the real world but appearing and behaving differently.
FIGURE 4.3
Prince of Persia, a fully 3D environment
ptg7947181 GAME WORLDS 89
C H A P T E R 4
When you first think about the dimensionality of your game space, don’t immedi- ately assume that you want it to be three-dimensional because 3D seems more real or makes the best use of your machine’s hardware. As with everything else you design, the dimensionality of your physical space must serve the entertainment value of the game. Make sure all the dimensions will contribute meaningfully.
Many games that work extremely well in two dimensions don’t work well in three.
Lemmings was a hit 2D game, but Lemmings 3D was nowhere near as successful because it was much more difficult to play. The addition of a third dimension detracted from the player’s enjoyment rather than added to it.