Communications: electrical – Land vehicle alarms or indicators – Internal alarm or indicator responsive to a condition of the...
Patent
1986-11-20
1989-05-09
Blum, Theodore M.
Communications: electrical
Land vehicle alarms or indicators
Internal alarm or indicator responsive to a condition of the...
340727, 340744, G09G 116
Patent
active
048292915
DESCRIPTION:
BRIEF SUMMARY
This invention relates to raster graphical display apparatus.
Computer graphics raster color display generators may be classified according to the following parameters:
(a) Spatial Resolution--This is the number of independently definable points or pixels in the x (along the scan lines) and y (normal to the scan lines) axes of the displayed picture.
(b) The number of simultaneous colors which may be displayed. This is determined by the number of bits defining each pixel of the screen, for example four bits allows 2 raised to the power of 4=16, simultaneous colors, 8 bits allow 2 raised to the power 8=256 simultaneous colors. The term bit plane, or simply plane, is used to describe the memory for one bit of the pixel with the x and y resolution defined in (a). linearly proportional to x,y and the number of bits per pixel.
Eight planes, allowing 256 colors to be present on the screen simultaneously, is adequate for most computer graphics such as computer aided design (CAD) and gray scale images but does not provide sufficient simultaneous colors for images with subtle coloring such as 3D shaded images. In such images, the distance from the viewer may be shown by fading the colors of parts of the image further from the viewer (called depth cueing) or effects such as reflection and transparency. To achieve subtle shading such as this requires 256 shades of red, 256 shades of blue and 256 shades of green simultaneously calling for 24 bits per pixel.
The cost of pixel store memory to provide twenty-four planes is prohibitive for applications which only occasionally require this subtle shading. Such applications are in CAD where much of the graphics consists of assembly drawings, architects drawing, machine drawings and wire frame 3D drawings. These do not require many simultaneous colors, but do require high resolution in x and y to display all of the detail.
Users often require to see a fully shaded, depth-cued 3D image after design to see what the room, building or complex machined part will look like once it has been fabricated. The user would normally produce a 24-bit image in the host computer using processing to remove the parts of the picture which are behind each other (called hidden surface removal) and to add effects such as room lighting, reflection and shadows. It would not normally be possible to display the result unless the graphics system provided 24 planes.
Users of raster graphics equipment require high resolution in x and y raster directions to be able to reproduce fine detail on, for example engineering drawings. It is also desirable to have many bit planes to achieve realistic subtle shading for example to display computer generated images of three-dimensional objects (24-bit planes are often used for this purpose). It is unusual to require both high resolution and many bit planes simultaneously and such equipment is expensive due to the amount of pixel store memory required.
According to this invention there is provided raster graphical display apparatus comprising means for providing, in a first mode, a video raster signal based on a resolution of x pixels per line and y lines, a pixel store arranged to provide n planes per pixel and thus 2.sup.n color possibilities per pixel, means for selecting a second mode to make available mn planes per macro-pixel in the pixel store, where m is an integer greater than 1 and m=m1.m2 where m1 is the dimension of each macro-pixel along the scan lines and expressed in pixels, and m2 is the dimension of each macro-pixel transverse to the scan lines and expressed in lines of the first mode raster.
In one arrangement, m1=2 and m2=2 but each line occurs twice in succession as a line pair (to preserve aspect ratio) to reduce the line resolution so that of the available 4n bit planes per macropixel only 2n are distributed between a plurality of color gun drive signals in the same way in both lines of each line pair.
In another preferred arrangement, the planes available per macro-pixel are allocated to different sets of color gun drive signals in respective co
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IBM Technical Disclosure Bulletin, vol. 23, No. 3, Aug. 1980, N. Y. Murphy: "Storage and Transmission Bandwidth Reduction for High Resolution Color and Monochrome Displays", pp. 1236-1237.
Computer Design, vol. 20, No. 7, Jul. 1981, Winchester, K. Dinwiddie: "Memory Organization and High Speed Processor Facilitate Unique Image Display Capabilities", pp. 115-116.
Elgood Mark C.
Jales Richard J.
Blum Theodore M.
Gregory Bernarr E.
Sigmex Limited
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