Isometric video game graphics

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Isometric video game graphics are graphics employed in video games and pixel art where the viewpoint is angled to reveal facets of the environment that would not be visible from a top-down perspective or side view, thereby producing a three-dimensional effect. Despite the name, isometric computer graphics are not necessarily truly isometric—i.e., the x, y, and z axes are not necessarily oriented 120° to each other. Instead, a variety of angles are used; some form of parallel projection, such as dimetric projection with a 2:1 pixel ratio, is the most common. The terms "3/4 perspective", "2.5D", and "pseudo-3D" are also sometimes used, although these terms can possess slightly different meanings in other contexts.

Once common, isometric projection became less common with the advent of more powerful 3D graphics systems, and as games began to focus more on action and individual characters.[1] However, video games using isometric projection have seen somewhat of a resurgence in recent years, especially on Kickstarter.[1][2]

Overview

True isometric drawing of a cube. Note the 120° angles separating the x, y and z axes, as well as the equal lengths of each of the cube's edges.
Common form of dimetric projection used in video games and pixel art. The angle 26.565° forms a 2:1 pixel ratio, and is equal to ${\displaystyle \arctan(0.5)}$.

In the fields of computer and video games and pixel art, the technique has become popular because of the ease with which 2D sprite- and tile-based graphics can be made to represent a 3D gaming environment. Because parallelly projected objects do not change size as they move about the game field, there is no need for the computer to scale sprites or do the complex calculations necessary to simulate visual perspective. This allowed older 8-bit and 16-bit game systems (and, more recently, handheld and mobile systems) to portray large 3D areas quickly and easily. And, while the depth confusion problems of parallel projection can sometimes be a problem, good game design can alleviate this.

There are also gameplay advantages to using an isometric or pseudo-isometric perspective in video games. For instance, compared to a purely top-down game, they add a third dimension, opening up new avenues for aiming and platforming.[1] Secondly, compared to a first- or third-person game, they allow you to more easily field and control a larger number of additional units, such as a full party of characters in a role-playing game.[1] Further, they may alleviate situations where a player may become distracted from a game's core mechanics by having to constantly manage an unwieldy 3D camera.[1] I.e. the player can focus on playing the game itself, and not on moving and rotating the camera.[1]

Lastly, there is an artistic advantage. Though not limited strictly to isometric video games, pre-rendered 2D graphics can possess a higher fidelity and use more advanced techniques than may be possible on commonly available computer hardware, even with 3D hardware acceleration enabled.[3] Similarly to modern CGI used in motion pictures, graphics can be rendered once on a powerful super computer or render farm, and then displayed on less powerful consumer hardware, such as tablet computers and Web browsers. This means that static pre-rendered isometric graphics often look better compared to their real-time rendered counterparts, and may age better over time compared to their peers.[2] However, this advantage may be less pronounced now than it was in the past.

One disadvantage of pre-rendered graphics is that, as display resolutions continue to increase, the static 2D images need to ideally be re-rendered to keep pace, or otherwise suffer from pixelation. This is not always possible, however; as was the case in 2012, when BioWare's Baldur's Gate (1998) was remade into Baldur's Gate: Enhanced Edition by the studio Beamdog. The new developer opted for simple 2D graphics scaling, or "zooming", without re-rendering the game's sprites, as they were lacking the game's original creative art assets. (The original data was lost in a flood.[4]) Changing the resolution of a real-time rendered game is trivial, in comparison.

Differences with "true" isometric projection

Corresponding 3D camera rotation angles for true isometric projection (at left) and the form of dimetric perspective commonly found in video games and pixel art (at right).[5] The angle 35.264° is equal to ${\displaystyle \arctan(\sin(45^{\circ }))}$.

The projection commonly used in videogames deviates slightly from "true" isometric due to the limitations of raster graphics. Lines in the x and y directions would not follow a neat pixel pattern if drawn in the required 30° to the horizontal. While modern computers can eliminate this problem using anti-aliasing, earlier computer graphics did not support enough colors or possess enough CPU power to accomplish this. So instead, a 2:1 pixel pattern ratio would be used to draw the x and y axis lines, resulting in these axes following a 26.565° (${\displaystyle \arctan(0.5)}$) angle to the horizontal. (Game systems that do not use square pixels could, however, yield different angles, including "true" isometric.) Therefore, this form of projection is more accurately described as a variation of dimetric projection, since only two of the three angles between the axes are equal to each other (116.565°, 116.565°, 126.870°).

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