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Pixel

From Sega Retro

Pixel is a contraction of Picture Element. A single, indivisible unit that makes up an image when used in conjunction with many (perhaps thousands or millions) other pixels. Typically, the visible part of the Mega Drive screen consists of 71,680 pixels, since it has a display resolution of 320×224.

Units

  • 1 megapixel (MPixel) = 1 million pixels
  • 1 gigapixel (GPixel) = 1 billion pixels (1000 MPixels)

Fillrate

The term fillrate refers to the number of pixels a video card or graphics chipset can render in a second, and the number of pixels it can write to video memory. This is also known as the rendering fillrate. Traditionally, fillrate was dependent on video memory bandwidth, the rate at which bytes can be written to, or read from, video memory, but this is no longer the case with modern GPU.

The terms effective fillrate and tile fillrate are used in reference to tilemap/scanline/tiled/deferred rendering engines which, through compression and other techniques, minimize the amount of pixels that need to be drawn on screen, read from memory, or written to memory, by rendering graphics data as tiles rather than pixels, thus reducing fillrate and bandwidth requirements to a small fraction/percentage of what would be required from traditional bitmap/framebuffer rendering engines. The fillrates of tiled rendering engines are usually measured in terms of tiles (ranging from 8×8 to 32×32 pixels each), thus the terms effective fillrate and tile fillrate refer to the equivalent amount of pixels that would be required from a traditional bitmap/framebuffer rendering engine to display the same amount of tiles as a tiled/scanline/deferred rendering engine. Several different forms of tiled rendering are supported by most Sega consoles, from the SG-1000 (1983) to the Dreamcast (1998), as well as most Sega arcade systems, from the G80 (1981) to the Aurora (2005).

Units

The units used to measure fillrate:

  • 1 megapixel/sec (MPixel/s) = 1 million pixels per second
  • 1 gigapixel/sec (GPixel/s) = 1 billion pixels per second (1000 MPixels/s)

Sega consoles

Fillrates for Sega home consoles:

  • SG-1000 (1983) and Master System (1985) — 5.3 MPixels/s (read), 2.3 MPixels/s (write)
  • Mega Drive (1988) — 6.9 MPixels/s (read), 6.4 MPixels/s (write), 6.9–36 MPixels/s (tile fillrate)
    • CD (1991) — 6.9 MPixels/s (read/write), 6.9–36 MPixels/s (tile fillrate)
    • 32X (1994) — 18 MPixels/s (32,768 colors/pixel), 36 MPixels/s (256 colors/pixel)
  • Saturn (1994) — 26–264 MPixels/s (bitmap fillrate), 280–570 MPixels/s (tile fillrate)
    • VDP1 — 28 MPixels/s (32,768 colors/pixel), 35 MPixels/s (256 colors/pixel)
    • VDP2 — 26–229 MPixels/s (bitmap fillrate), 251–534 MPixels/s (tile fillrate)
  • Dreamcast (1998) — 3.2 GPixels/s (opaque), 500 MPixels/s (opaque/translucent)

For the fillrates of Sega arcade systems, see individual arcade article pages listed at List of Sega arcade systems.

Texel

A texel (texture element or texture pixel) is the fundamental unit of texture space. Textures are represented by arrays of texels, just as pictures are represented by arrays of pixels. It is primarily used in reference to texture-mapped polygons, but can also be used in reference to sprites or tiles.

Units

  • 1 megatexel (MTexel) = 1 million texels
  • 1 gigatexel (GTexel) = 1 billion texels (1000 MTexels)

Texture fillrate

  • 1 megatexel/sec (MTexel/s) = 1 million texels per second
  • 1 gigatexel/sec (GTexel/s) = 1 billion texels per second (1000 MTexels/s)

The texture fillrate is usually the same as the rendering fillrate, especially for 2D graphics, but can differ for 3D graphics.