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(11) | EP 0 280 582 A3 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Improvements in computer graphics systems |
| (57) A multi-tasking, multiple windowing computer graphics facility which does not place
undue burdens upon the processing power of its host computer comprises a multi-planar
memory to which data defining windows to be displayed in viewports on a display screen
can be written, and a plurality of viewport controllers each individually associated
with a respective one of the memory planes and capable of extracting data from each
of a plurality of windows defined in its respective memory plane for effecting a corresponding
display in any desired viewport location on the display screen. For the management
of overlapping viewports, the window-viewport assignments which determine the display
locations of viewports on the display screen include viewport priority indications
which are taken into account in the reading out of data from the several planes of
the multi-planar memory so that overlapping viewports are handled automatically and
can appear transparent or opaque relative to one another as required. Windows can
be created of any size and any number of planes deep (up to the available depth of
the display memory), and opaque or transparent images can be moved freely around the
display screen without requiring modification of the data In the memory by flexibly
mapping windows in the display memory to viewports on the screen. A VRAM (video RAM),
multi-planar memory is used and the viewport controllers are configured as modular
VLSI components which can be cascaded for addressing any number of memory planes. |