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Planar (computer graphics)

In computer graphics, planar is the method of representing pixel colours with several bitplanes of RAM. Each bit in a bitplane is related to one pixel on the screen. Unlike Chunky, Highcolour or Truecolour graphics, the whole data for an individual pixel isn't in one specific location in RAM, but spread across the bitplanes that make up the display.

This scheme originated in the early days of computer graphics, when available memory chips could not supply data fast enough on their own to generate a picture on a TV screen or monitor from a large framebuffer. By splitting the data up into multiple planes, each plane could be stored on a separate memory chip. These chips could then be read in parallel at a slower rate, allowing graphical display on modest hardware. The EGA video adapter on early IBM PC computers used planar arrangement in colour graphical modes for this reason. When the later VGA was introduced, it included one non-planar mode which sacrificed memory efficiency for more convenient access.

For example, on a chunky display, each byte represents one pixel. Three pixels in a row would be stored as follows, where up to 256 different colours are available:

Byte index




Value (binary)




Value (decimal)




Resulting pixel




Whereas a planar data store could use 2 bitplanes, providing for a 4 colour display:

Byte index

colspan=8| 0

Bit index


Plane 0


Plane 1


Resulting pixel


Byte value

colspan=8 style="text-align: center;"| 146

Adding a third plane would make 2=8 colours available. Where fewer than 256 colours are needed, planar graphics are more economical in RAM compared with 8-bit chunky graphics, as there are no unused bits in a given byte.

A disadvantage of planar graphics is that more RAM address cycles are needed for scrolling and animations, although these operations can be made faster by dedicated hardware such as the blitter chips used in Amiga and some later Atari ST computers.



a. 1 Of or pertaining to a plane. 2 flat, two-dimensional. 3 (context graph theory of a graph English) Able to be embedded in the plane with no edges intersecting. 4 (context transistor chip semiconductor devices English) Having a flat profile, not etched into a mesa.

Douglas Harper's Etymology Dictionary


1850, from Latin planaris "level, flat," from planum "plane" (see plane (n.1)).



adj. involving two dimensions [syn: two-dimensional] [ant: cubic, linear]

Usage examples of "planar".

Among the knowledge that had been revealed to him was an understanding of the nature of the planar fabric, and an ability to use that fabric to suit his own ends.

Hobarth walked the dark passages between this world and the next, following the contours of the planar fabric that allowed him to enter in one place and emerge in a different location when he returned to the Realms.

A few moments later, the great panther was running off through the planar tunnel to its astral home, and Drizzt moved along the trails leading to the human village and his answers.

Soliloquized parody of a broadcast-television advertisement for shampoo, utilizing four convex mirrors, two planar mirrors, and one actress.

The smooth ride of the planar tunnel transformed into a nightmarish bounce and skip, with Regis hurtling head over heels and deflecting off the walls, which twisted suddenly, as if to deny him passage.

In his other hand the barbarian held Aegis-fang ready, not wanting to swing through the planar portal but hoping for something more vulnerable than an arm to come through to his world.

He met no further resistance for many minutes and understood why when he at last reached the planar gate.

His goal, too, was singular: the little patch of light in the gloom, the planar gate back to his own world.

Wulfgar averted his eyes at the horrid spectacle of a winged demodand caught within the warping planar tunnel, bent and bowed until its skin began to rip apart.

Apparently the glassy image of the planar portal had been more than just an image.

However, many of them had orbits well outside the ecliptic and that helped to make the search every bit as difficult as it would have been with a greater number of comet nuclei but in a more planar cloud.

Chase quizzed the cadet about planar changes and burn schedules until he satisfied himself that she knew her textbooks.

Tsiolkovskigrad, but would not have a launch window to SPS-5 for another forty-five minutes and their minimum-time trajectory required a fuel-slurping planar change.

Once we go beyond planar surfaces we see how mysterious a subject is the geometry of space and time.

His face had a hewn masculinity to it, planar and strong, and nothing detracted from the way he looked in her eyes, not even the soot on his face and the water dripping from his hair.