Sprite (computer Graphics) - Move To 3D

Move To 3D

Prior to the popularizing of true 3D graphics in the late 1990s, many 2D games attempted to imitate the look of three-dimensionality with a variety of sprite production methods. These included:

  • Rotoscoping: The filmed performances of live actors were sometimes used for creating sprites, most famously in the case of Prince of Persia which added a relative element of realism to a platform game. The method was used in a number of other fighting games, mostly in the mid 1990s.
  • Claymation or the use of posable models which were used for characters that could not be portrayed by actors. Famous early examples include Goro of Mortal Kombat and various enemies from Doom. Used to a greater extent in games like Clay Fighter.
  • Pre-rendered CGI models: Introduced by Rise of the Robots and made famous by Donkey Kong Country, and later used to a great extent in PC real-time strategy and role-playing video game games prior to the move to real-time 3D. Since computers of the day could not run complex 3D graphics, footage of pre-rendered three-dimensional character models were often used which created a (relative) illusion of 3D.

More often sprite now refers to a partially transparent two dimensional animation that is mapped onto a special plane in a 3D scene. Unlike a texture map, the sprite plane is always perpendicular to the axis emanating from the camera. The image can be scaled to simulate perspective, rotated two dimensionally, overlapped with other objects, and be occluded, but it can only be viewed from a single angle. This rendering method is also referred to as billboarding.

Sprites create an effective illusion when

  • the image inside the sprite already depicts a three dimensional object;
  • the animation is constantly changing or depicts rotation;
  • the sprite exists only shortly;
  • the depicted object has a similar appearance from many common viewing angles (such as something spherical);
  • the perspective of the object from the viewer cannot possibly change fast enough for the viewer to discern a difference from true 3D geometry, as in the case of object a long distance away from the viewer in 3D space.
  • the viewer accepts that the depicted object only has one perspective (such as small plants or leaves).

When the illusion works, viewers will not notice that the sprite is flat and always faces them. Often sprites are used to depict phenomena such as fire, smoke, small objects, small plants (like blades of grass), or special symbols (like "1-Up"), or object of any size where the angle of view does not appreciably change with respect to the rectilinear projection of the object (usually from a long distance). The sprite illusion can be exposed in video games by quickly changing the position of the camera while keeping the sprite in the center of the view. Sprites are also used extensively in particle effects and commonly represented pickups in early 3D games especially.

An example of extensive usage of sprites to create the illusion is the game The Elder Scrolls IV: Oblivion, whose main graphical feature was the ability to display hundreds, if not thousands of animated trees on-screen at one time. Closer inspection of those trees reveals that the leaves are in fact sprites, and rotate along with the position of the user. The tree rendering package used by Oblivion uses sprites to create the appearance of a high number of leaves. However, this fact is only revealed when the player actually examines the trees up-close, and rotates the camera.

Sprites have also occasionally been used as a special-effects tool in movies. One such example is the fire breathing Balrog in The Lord of the Rings: The Fellowship of the Ring; the effects designers utilized sprites to simulate fire emanating from the surface of the demon. Small bursts of fire were filmed in front of a black background and made transparent using a luma key. Many bursts were then attached to the surface of the animated Balrog model and mixed with simulated smoke and heat waves to create the illusion of a monster made from fire.

The term sprite is often confused with low resolution 2D graphics drawn on a computer, also known as pixel art. However, sprite graphics (bitmaps) can be created from any imaginable source, including prerendered CGI, dynamic 3D graphics, vector art, and even text. Likewise, pixel art is created for many purposes other than as a sprite, such as video game backgrounds, textures, icons, websites, display art, comics, and t-shirts.

With the advancement in computer graphics and improved power and resolution, actual pixel art sprites are becoming increasingly infrequent outside of handheld game systems and cell phones.

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