Hardware Sprites
In early video gaming, hardware sprites were a method of compositing separate bitmaps so that they appear to be part of a single image on a screen.
Many early graphics chips had true spriting use capabilities in which the sprite images were integrated into the screen, often with priority control with respect to the background graphics, at the time the video signal was being generated by the graphics chip.
These contrasted with software and blitter methods of 2d animation which modify a framebuffer held in RAM, which required more memory cycles to load and store the pixels,sometimes with an additional mask, and refresh backgrounds behind moving objects. These methods frequently required double buffering to avoid flickering and tearing, but placed fewer restrictions on the size and number of moving objects.
The sprite engine is a hardware implementation of scanline rendering. For each scanline the appropriate scanlines of the sprites are first copied (the number of pixels is limited by the memory bandwidth and the length of the horizontal retrace) into very fast, small, multiple (limiting the number of sprites on a line), and costly caches (the size of which limit the horizontal width) and as the pixels are sent to the screen, these caches are combined with each other and the background. It may be larger than the screen and is usually tiled, where the tile map is cached, but the tile set is not. For every pixel, every sprite unit signals its presence onto its line on a bus, so every other unit can notice a collision with it. Some sprite engines can automatically reload their "sprite units" from a display list. The sprite engine has synergy with the palette. To save registers, the height of the sprite, the location of the texture, and the zoom factors are often limited. On systems where the word size is the same as the texel there is no penalty for doing unaligned reads needed for rotation. This leads to the limitations of the known implementations:
| Computer, chip | Year | Sprites on screen | Sprites on line | Max. texels on line | Texture width | Texture height | Colors | Hardware zoom | Rotation | Background | Collision detection | Source | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Amiga, Denise | 1985 | Display list | 8 | ? | 16 | Arbitrary | 3, 15 | Vertical by display list | No | 2 bitmap layers | Yes | Color key | |
| Amiga (AGA), Lisa | 1992 | Display list | 8 | ? | 16, 32, 64 | Arbitrary | 3, 15 | Vertical by display list | No | 2 bitmap layers | Yes | Color key | |
| Amstrad Plus, Asic | 1990 | Display list run by CPU | 16 min. | ? | 16 | 16 | 15 | 1, 2, 4x vertical, 1, 2, 4x horizontal | No | Bitmap layer | No | Color key | |
| Atari 2600, TIA | 1977 | Multiplied by CPU | 9 (with triplication) | 51 (with triplication) | 1, 8 | 262 | 1 | 1, 2, 4, 8× horizontal | horizontal mirroring | 1 bitmap layer | Yes | Color key | |
| Atari 8-bit, GTIA/ANTIC | 1979 | Display list | 8 | 40 | 2, 8 | 128, 256 | 1,3 | 1, 2× vertical, 1, 2, 4x horizontal | No | 1 tile or bitmap layer | Yes | Color key | |
| C64, VIC-II | 1982 | Display list run by CPU | 8 | 96, 192 | 12, 24 | 21 | 1, 3 | 1, 2× integer | No | 1 tile or bitmap layer | Yes | Color key | |
| Game Boy | 1989 | 40 | 10 | 80 | 8 | 8, 16 | 3 | No | No | 1 tile layer | No | Color key | |
| GBA | 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 | |
| Gameduino | 2011 | 256 | 96 | 1,536 | 16 | 16 | 255 | No | Yes | 1 tile layer | Yes | Color key | |
| NES, RP2C0x | 1983 | 64 | 8 | 64 | 8 | 8, 16 | 3 | No | No | 1 tile layer | Partial | Color key | |
| Neo Geo | 1990 | 384 | 96 | 1536 | 16 | Up to 512 | 15 | sprite shrinking | No | No | No | Color key | . |
| Out Run, dedicated hardware | 1986 | 128 | 32 | ? | 8 | 8 | ? | Yes anisotropic | No | 3 tile layers | ? | Alpha | |
| PC Engine, HuC6270A | 1987 | 64 | 16 | 256 | 16, 32 | 16, 32, 64 | 15 | No | No | 1 tile layer | Yes | Color key | |
| 1985 | 64 | 8 | 64 | 8 | 8, 16 | 15 | 1, 2× integer | No | 1 tile layer | Yes | Color key | ||
| Mega Drive | 1988 | 80 | 20 | 320 | 8, 16, 24, 32 | 8, 16, 24, 32 | 15 | No | No | 2 tile layers | Yes | Color key | |
| Sharp X68000 | 1987 | 128 | 32 | ? | 16 | 16 | 15 | No | No | ? | ? | Color key | |
| SNES | 1990 | 128 | 34 | 272 | 8, 16, 32, 64 | 8, 16, 32, 64 | 15 | Background only | Background only | 3 tile layers or 1 affine mapped tile layer | Yes | Color key, averaging | |
| Texas Instruments TMS9918 | 1979 | 32 | 4 | 64 | 8, 16 | 8, 16 | 1 | 1, 2× integer | No | 1 tile layer | Partial | Color key | |
| 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 | |
| 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 | |
| Computer, chip | Year | Sprites on screen | Sprites on line | Max. texels on line | Texture width | Texture height | Colors | Hardware zoom | Rotation | Background | Collision detection | Source |
Many third party graphics cards offered sprite capabilities. Sprite engines often scale badly, starting to flicker as the number of sprites increases above the number of sprite units, or uses more and more silicon as the designer of the chip implements more units and bigger caches.
Read more about this topic: Sprite (computer Graphics), History
Famous quotes containing the word hardware:
“A friend of mine spoke of books that are dedicated like this: “To my wife, by whose helpful criticism ...” and so on. He said the dedication should really read: “To my wife. If it had not been for her continual criticism and persistent nagging doubt as to my ability, this book would have appeared in Harper’s instead of The Hardware Age.””
—Brenda Ueland (1891–1985)