Sprite (computer graphics)
In computer graphics, a sprite is a two-dimensional bitmap that is integrated into a larger scene, most often in a 2D video game. The term was first used by Danny Hillis at Texas Instruments in the late 1970s.[1] Originally, the term "sprites" referred to fixed-sized objects composited together, by hardware, with a background.[2] Use of the term has since become more general.
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Systems with hardware sprites include the TI-99/4A (1979), Atari 8-bit family (1979), Commodore 64 (1982), Nintendo Entertainment System (1983), Amiga (1985), Sega Genesis (1988), and arcade games of the 1970s and 1980s. Hardware varies in the number of sprites supported, how many can be displayed per scan line (often a lower number), the size and colors of each sprite, and special effects such as scaling or reporting pixel-precise overlap.
Hardware composition of sprites occurs as each scan line is prepared for the video output device, such as a CRT, without involvement of the main CPU and without the need for a full-screen frame buffer.[2] Sprites can be positioned or altered by setting attributes used during the hardware composition process.
The CPUs in modern computers, video game consoles, and mobile devices are fast enough that bitmaps can be composited without special hardware assistance; alternatively, modern GPUs can perform compositing of vast numbers of scaled, rotated, antialiased, and partially translucent images in parallel with the CPU.
History
The use of sprites originated with arcade games. The first video game to represent player characters as human player images was Taito's Basketball, which was licensed in February 1974 to Midway, releasing it as TV Basketball in North America.[3][4]
Signetics devised the first chips capable of generating sprite graphics (referred to as objects by Signetics) for home systems. The Signetics 2636 video processors were first used in the 1978 1292 Advanced Programmable Video System and later in the 1979 Elektor TV Games Computer.
The Atari VCS, released in 1977, features a hardware sprite implementation where five graphical objects can be moved independently of the game playfield. The term sprite was not in use at the time. The VCS's sprites are called movable objects in the programming manual, further identified as two players, two missiles, and one ball.[5] These each consist of a single row of pixels that are displayed on a scan line. To produce a two-dimensional shape, the sprite's single-row bitmap is altered by software from one scan line to the next.
The 1979 Atari 400 and 800 home computers feature similar, but more elaborate, circuitry capable of moving eight single-color objects per scan line: four 8-bit wide players and four 2-bit wide missiles. Each is the full height of the display—a long, thin strip. DMA from a table in memory automatically sets the graphics pattern registers for each scan line. Hardware registers control the horizontal position of each player and missile. Vertical motion is achieved by moving the bitmap data within a player or missile's strip. The feature was called player/missile graphics by Atari.
The Namco Galaxian arcade system board, for the 1979 arcade game Galaxian, featured animated, multi-colored sprites.[6] It pioneered a sprite system that animated pre-loaded sprites over a scrolling background, which became the basis for Nintendo's Radar Scope and Donkey Kong arcade hardware and home consoles such as the Nintendo Entertainment System.[7] According to Steve Golson from General Computer Corporation, the term "stamp" was used instead of "sprite" at the time.[8]
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).[9] 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.
Systems with hardware sprites
These are base hardware specs and do not include additional programming techniques, such as using raster interrupts to repurpose sprites mid-frame.
Computer system | Sprite hardware | Year | Sprites on screen | Sprites on line | Max. texels on line | Texture width | Texture height | Colors | Hardware zoom | Rotation | Background | Collision detection | Transparency | Source |
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Amstrad Plus | 1990 | 16 | 16 | ? | 16 | 16 | 15 | 1, 2, 4× vertical, 1, 2, 4× horizontal | No | 1 bitmap layer | No | Color key | [10] | |
Atari 2600 | TIA | 1977 | 5 | 5 | 19 | 1, 8 | 262 | 1 | 1, 2, 4, 8× horizontal | Horizontal mirroring | 1 bitmap layer | Yes | Color key | [11] |
Atari 8-bit family | GTIA/ANTIC | 1979 | 8 | 8 | 40 | 2, 8 | 128, 256 | 1 | 1, 2× vertical, 1, 2, 4× horizontal | No | 1 tile or bitmap layer | Yes | Color key | [12] |
Commodore 64 | VIC-II | 1982 | 8 | 8 | 96, 192 | 12, 24 | 21 | 1, 3 | 1, 2× integer | No | 1 tile or bitmap layer | Yes | Color key | [13] |
Amiga (OCS) | Denise | 1985 | Arbitrary | 8 | 128 | 16 | Arbitrary | 3, 15 | Vertical by display list | No | 2 bitmap layers | Yes | Color key | [14] |
Amiga (AGA) | Lisa | 1992 | Arbitrary | 8 | 512 | 16, 32, 64 | Arbitrary | 3, 15 | Vertical by display list | No | 2 bitmap layers | Yes | Color key | |
Colecovision | Texas Instruments TMS9918A | 1983 | 32 | 4 | 64 | 8, 16 | 8, 16 | 1 | 1, 2× integer | No | 1 tile layer | Partial | Color key | |
Texas Instruments TI-99/4A | Texas Instruments TMS9918A | 1981 | 32 | 4 | 64 | 8, 16 | 8, 16 | 1 | 1, 2× integer | No | 1 tile layer | Partial | Color key | |
Gameduino | 2011 | 256 | 96 | 1,536 | 16 | 16 | 255 | No | Yes | 1 tile layer | Yes | Color key | [15] | |
Intellivision | STIC AY-3-8900 | 1979 | 8 | 8 | 64 | 8 | 8,16 | 1 | 1, 2, 4, 8× vertical, 1, 2× horizontal | Horizontal and vertical mirroring | 1 tile layer | Yes | Color key | [16] |
MSX | Texas Instruments TMS9918A | 1983 | 32 | 4 | 64 | 8, 16 | 8, 16 | 1 | 1, 2× integer | No | 1 tile layer | Partial | Color key | [17] |
MSX2 | Yamaha V9938 | 1986 | 32 | 8 | 128 | 8, 16 | 8,16 | 1, 3, 7, 15 per line | 1, 2× integer | No | 1 tile or bitmap layer | Partial | Color key | |
MSX2+ / MSX turbo R | Yamaha V9958 | 1988 | 32 | 8 | 128 | 8,16 | 8,16 | 1, 3, 7, 15 per line | 1, 2× integer | No | 1 tile or bitmap layer | Partial | Color key | |
Namco Pac-Man (arcade) | TTL | 1980 | 6 | 6 | 96 | 16 | 16 | 3 | No | Horizontal and vertical mirroring | 1 tile layer | No | Color key | [18] |
TurboGrafx-16 | HuC6270A | 1987 | 64 | 16 | 256 | 16, 32 | 16, 32, 64 | 15 | No | No | 1 tile layer | Yes | Color key | |
Namco Galaxian (arcade) | TTL | 1979 | 7 | 7 | 112 | 16 | 16 | 3 | No | Horizontal and vertical mirroring | 1 tile layer | No | Color key | [19][20][21] |
Nintendo Donkey Kong, Radar Scope (arcade) | 1979 | 128 | 16 | 256 | 16 | 16 | 3 | Integer | No | 1 tile layer | Yes | Color key | [22] | |
Nintendo DS | Integrated PPU | 2004 | 128 | 128 | 1,210 | 8, 16, 32, 64 | 8, 16, 32, 64 | 65,536 | Yes, affine | Yes, affine | 4 layers per screen; each layer is independent | No | Color key, blending | [23] |
NES/Famicom | Ricoh RP2C0x PPU | 1983 | 64 | 8 | 64 | 8 | 8, 16 | 3 | No | Horizontal and vertical mirroring | 1 tile layer | Partial | Color key | [24] |
Game Boy | Integrated PPU | 1989 | 40 | 10 | 80 | 8 | 8, 16 | 3 | No | Horizontal and vertical mirroring | 1 tile layer | No | Color key | [25] |
Game Boy Advance | Integrated PPU | 2001 | 128 | 128 | 1210 | 8, 16, 32, 64 | 8, 16, 32, 64 | 15, 255 | Yes, affine | Yes, affine | 4 layers, 2 layers, and 1 affine layer, 2 affine layers | No | Color key, blending | [26] |
Master System, Game Gear | VDP (TMS9918-derived) | 1985 | 64 | 8 | 128 | 8, 16 | 8, 16 | 15 | 1, 2× integer, 1, 2× vertical | Background tile mirroring | 1 tile layer | Yes | Color key | [27][28] |
Sega Genesis | YM7101 VDP (SMS VDP-derived) | 1988 | 80 | 20 | 320 | 8, 16, 24, 32 | 8, 16, 24, 32 | 15 | No | Horizontal and vertical mirroring | 2 tile layers | Yes | Color key | [29][30] |
Sega OutRun (arcade) | 1986 | 128 | 128 | 1600 | 8 to 512 | 8 to 256 | 15 | Yes, anisotropic | Horizontal and vertical mirroring | 2 tile layers and 1 bitmap layer | Yes | Alpha | [31][32][33][34][35][36][37] | |
Sharp X68000 | Cynthia jr. (original), Cynthia (later models) | 1987 | 128 | 32 | 512 | 16 | 16 | 15 | 1, 2× integer | Horizontal and vertical mirroring | 1-2 tile layers and 1-4 bitmap layers | Partial | Color key | [38][39][40] |
Neo Geo | LSPC2-A2 | 1990 | 384 | 96 | 1536 | 16 | 16 to 512 | 15 | Sprite shrinking | Horizontal and vertical mirroring | 1 tile layer | Partial | Color key | [41][42][43] |
Super NES/ Super Famicom | S-PPU1, S-PPU2 | 1990 | 128 | 34 | 272 | 8, 16, 32, 64 | 8, 16, 32, 64 | 15 | Background only | Horizontal and vertical mirroring | 3 tile layers or 1 affine mapped tile layer | Yes | Color key, averaging | |
Computer system | Sprite hardware | Year | Sprites on screen | Sprites on line | Max. texels on line | Texture width | Texture height | Colors | Hardware zoom | Rotation | Background | Collision detection | Transparency | Source |
Use in 3D rendering
2D images with alpha channels constrained to face the camera may be used in 3D graphics. They are common for rendering vegetation, to approximate distant objects, or for particle effects. These are sometimes called "billboards" or "Z-sprites". If rendered on the fly to cache an approximate view of an underlying 3D model, such sprites are called impostors.[44] Modern GPU hardware can mimic sprites with two texture-mapped triangles or specific primitives such as point sprites.
Synonyms
Some hardware makers used terms other than sprite.
Player/Missile Graphics was a term used by Atari, Inc. for hardware-generated sprites in the Atari 8-bit computers and Atari 5200 console.[45] The term reflected the usage for both characters ("players") and smaller associated objects ("missiles") that share the same color. The earlier Atari 2600 and some Atari arcade games also used player, missile, and ball for sprites.
Movable Object Block, or MOB, was used in MOS Technology's graphics chip literature (data sheets, etc.) However, Commodore, the main user of MOS chips and the owner of MOS for most of the chip maker's lifetime, used the term sprite for the Commodore 64.
The developer manuals for the Nintendo Entertainment System, Super NES, and Game Boy refer to sprites as OBJs (short for "objects"), and the region of RAM used to store sprite attributes and coordinates was known as OAM (Object Attribute Memory). This also applies on the Game Boy Advance and Nintendo DS handheld systems.
See also
References
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