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In computer graphics, a sprite (also known by other names; see Synonyms below) is a two-dimensional image or animation that is integrated into a larger scene. Initially including just graphical objects handled separately from the memory bitmap of a video display, this now includes various manners of graphical overlays. Originally, sprites were a method of integrating unrelated bitmaps so that they appeared to be part of the normal bitmap on a screen, such as creating an animated character that can be moved on a screen without altering the data defining the overall screen. Such sprites can be created by either electronic circuitry or software. In circuitry, a hardware sprite is a hardware construct that employs custom DMA channels to integrate visual elements with the main screen in that it super-imposes two discrete video sources. Software can simulate this through specialized rendering methods. More recently, CSS sprites are used in web design as a way to improve performance by combining numerous small images or icons into a larger image called a sprite sheet or tile set, and selecting which icon to show on the rendered page using Cascading Style Sheets. As three-dimensional graphics became more prevalent, sprites came to include flat images seamlessly integrated into complicated three-dimensional scenes. == History == In the mid-1970s, Signetics devised the first video/graphics processors capable of generating sprite graphics. The Signetics 2636 video processors were first used in the 1976 Radofin 1292 Advanced Programmable Video System. The Atari VCS, released in 1977, features a hardware sprite implementation wherein five graphical objects can be moved independently of the game playfield. The VCS's sprites, called players and missiles, are constructed from a single row of pixels that displayed on a scan line; to produce a two-dimensional shape, the sprite's single-row bitmap is altered by software from one scanline to the next. The Atari 400 and 800 home computers of 1979 feature similar, but more elaborate circuitry, capable of moving eight Player/Missile objects per scanline - four 8-bit wide players, and four 2-bit wide missiles. This more advanced version allows operation like the VCS where the CPU modifies the graphics pattern register for each scan line, or an automatic mode where the display chip performs DMA from a table in memory populating the graphics pattern registers for each scan line. In the automatic DMA mode vertical motion is simulated by moving the sprites up and down incrementally in memory. The hardware produces a two-dimensional bitmap several pixels wide, and as tall as the screen. The width of pixels can also vary from 1, 2, or 4 color clocks. Multiple Player objects can be merged to produce a multi-color player. The four missile objects can be grouped together as a fifth Player and colored independently from the Players. The Elektor TV Games Computer was an early microcomputer capable of generating sprite graphics, which Signetics referred to as "objects". The term ''sprite'' was first used in the graphic sense by one of the definers of the Texas Instruments 9918(A) video display processor (VDP). The term was derived from the fact that sprites, rather than being part of the bitmap data in the framebuffer, instead "floated" around on top without affecting the data in the framebuffer below, much like a ghost or "sprite". By this time, sprites had advanced to the point where complete two-dimensional shapes could be moved around the screen horizontally and vertically with minimal software overhead. The CPU would instruct the external chips to fetch source images and integrate them into the main screen using direct memory access channels. Calling up external hardware, instead of using the processor alone, greatly improved graphics performance. Because the processor was not occupied by the simple task of transferring data from one place to another, software could run faster; and because the hardware provided certain innate abilities, programs were also smaller. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Sprite (computer graphics)」の詳細全文を読む スポンサード リンク
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