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AssigneeInternational Business Machines Corporation
InventorWilliam J. Fitzgerald, Jr.
Estimating the term…
A method and apparatus for determining the X--Y coordinates on the raster of the intersection of two curves one of which is stored in the display system raster refresh buffer. The second curve is generated by a curve generator or some other source of sequential X--Y coordinate data defining the X--Y coordinates on the raster where the second curve would lie. As each X--Y coordinate is generated by curve generator it is translated into a buffer address and the contents of that address in the buffer memory are accessed and a determination is made to see if said first curve exists at that address. If an element of the first curve is found to exist in the buffer store at the generated address location, it is known an intersection point has been found and the appropriate X--Y address is gated from the system to utilization means. According to a further feature of the invention, if a plurality of intersection points are found for two particular curves, averaging means are provided for at least approximating the midpoint of the actual intersection of the two curves and said midpoint address is gated out of the system as the intersection point. A method and means are also provided for determining if two curves have a point of tangency when they exist on two adjacent raster lines but do not actually intersect.
In a buffer refreshed raster type display system including an X-Y addressable raster refresh display buffer, a raster type TV display tube, raster generating circuitry, a source of curve coordinate data for providing a sequence of X-Y addresses in the display coordinates defining a desired curve, and a buffer address generator which translates the series of specific X-Y addresses produced by the curve data source into the appropriate buffer address where the curve data is to be stored, and synchronizing circuitry for controlling the raster generating circuitry and the buffer address generation and access, the improvement which comprises means for determining the intersection coordinates of a first curve currently stored in the raster refresh buffer and a second curve provided by said curve data source, said means for determining comprising, means for causing said curve data source to produce said sequential X-Y addresses defining said second curve, means for converting these addresses into raster refresh buffer addresses, means for accessing said buffer at each generated address, means for determining if there is data stored in said buffer indicative of the existence of the first curve, means for accessing the X-Y addresses when a successful determination is made which addresses comprise the intersection coordinates of the two curves.
In a buffer refreshed raster type display system including an X-Y addressable raster refresh buffer, a raster type TV display and associated raster generating circuitry, a source of curve coordinate data for providing a sequence of X-Y addresses in the display coordinates defining a desired curve, and a buffer address generator which translates a series of specific X-Y addresses produced by the curve data source into appropriate buffer addresses where the generated curve is to be stored and synchronizing circuitry for controlling the raster generating circuitry, the buffer address generation, and buffer access, the improvement which comprises means for determining the intersection coordinates of two curves displayable by the system, said means including,
Dependencies are inferred from the claim text.