VIRTUAL DISPLAY ADAPTER
    4.
    发明专利

    公开(公告)号:CA1313415C

    公开(公告)日:1993-02-02

    申请号:CA589106

    申请日:1989-01-25

    Applicant: IBM

    Abstract: Y0988-006 A display control means such as a virtual display adapter allows the advanced functions of a display controller to be utilized in a large area of memory in addition to the normal use in display memory. This large area of memory includes system memory, and efficient access to this large area of memory is permitted for normal system use. The display controller also functions with non-contiguous and non-resident bitmaps. The flexibility of demand-paged virtual memory is utilized for display tasks, as display bitmaps may be written to the large area of memory as well as the display memory.

    APPARATUS AND METHOD FOR RELATING A POINT OF SELECTION TO AN OBJECT IN A GRAPHICS DISPLAY SYSTEM

    公开(公告)号:CA2051176A1

    公开(公告)日:1992-04-13

    申请号:CA2051176

    申请日:1991-09-11

    Applicant: IBM

    Abstract: AT9-90-002 APPARATUS AND METHOD FOR RELATING A POINT OF SELECTION TO AN OBJECT IN A GRAPHICS DISPLAY SYSTEM Apparatus and methods for picking three dimensional objects from images depicted on a video display. The displayed objects are selectively rerendered. During such rerendering the object pixels are compared in depth to the data in a Z buffer for determining visibility. The number and size of the objects subject to rerendering by the rasterization processor is constrained by using the front end graphics processor to define object extents and by rerendering only extents which have been clipped to the boundaries of the pick window. The rerendering operation does not alter the three dimensional graphics image stored in and repetitively scanned from the frame buffer. Selection between multiple objects within the pick window can include a weighted comparison using a pick plane memory to store visibility data by object.

    DUAL PURPOSE SCREEN/MEMORY REFRESH COUNTER

    公开(公告)号:CA1236599A

    公开(公告)日:1988-05-10

    申请号:CA495677

    申请日:1985-11-19

    Applicant: IBM

    Abstract: DUAL PURPOSE SCREEN/MEMORY REFRESH COUNTER A counter is used to concurrently refresh a video display and a memory associated with such video display. Address bits are output from the counter to the sync decode logic used to refresh the display as well as to multiplexing means connected to the associated memory. The multiplexing means has three pairs of inputs. The first pair of inputs comprises refresh addresses from the counter for refreshing the memory array. The second pair of inputs to the multiplexing means comprises memory update addresses for writing new information into the memory. A third pair of inputs to the multiplexing means performs two functions. The first function enables the multiplexing means to output either the update addresses or the refresh addresses depending on the state of such inputs. The second function of the third pair of inputs is to identify the output of said multiplexing means as either a row address or a column address to the associated memory. The apparatus and technique disclosed herein is especially pertinent when a "nibble mode" dynamic RAM is used as the memory.

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