Sprite (computer graphics)

The term sprite is used in computer graphics to refer to a two dimensional image or animation that is integrated into a larger scene.

Related Topics:
Computer graphics - Image - Animation

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Sprites were originally invented as a method of quickly compositing several images together in two-dimensional video games using special hardware. As computer performance improved, this optimization became unnecessary and the term evolved to refer specifically to the two dimensional images themselves that were integrated into a scene. That is, figures generated by either custom hardware or by software alone were all referred to as sprites. As three-dimensional graphics became more prevalent, the term was used to describe a technique whereby flat images are seamlessly integrated into complicated three-dimensional scenes.

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More often a sprite now refers to a partially transparent two dimensional animation that is mapped onto a special plane in a three dimensional 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, it can be rotated two dimensionally, it can overlap other objects and be occluded, but it can only ever be viewed from the same angle. This rendering method is also referred to as billboarding.

Related Topics:
Texture map - Perspective - Occluded - Rendering

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Sprites create an effective illusion when:

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• the image inside the sprite already depicts a three dimensional object
• the animation is constantly changing or depicts rotation
• the sprite exists only for a short period of time
• the depicted object has a similar appearance from many common viewing angles (such as something spherical)
• 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"). 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.

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Sprites have also occasionally been used as a special effects tool in movies. Most notably, the creators of the fire breathing Balrog in ' used 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.

Related Topics:
Balrog - Luma key

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Sprite (computer graphics): Billboarding ►