Apparatus and method for using a test window in a graphics subsystem which incorporates hardware to perform clipping of images

Claim 1

An apparatus for performing comparisons between pairs of X and Y coordinates of an object to be displayed by a graphics subsystem, pairs of predetermined clip coordinates and pairs of predetermined offsets, and generating a plurality of signals representing the results of said comparisons, said object being one of a quadrilateral to be drawn and a block image to be moved, said apparatus having a clip window with predetermined top, bottom right and left clip coordinates, said apparatus comprising: a) a plurality of object coordinate registers; b) a plurality of clip coordinate register; c) a plurality of offset registers; d) loading means comprising a first multiplexor coupled to the plurality of object coordinate registers, the plurality of clip coordinate registers and the plurality of offset registers, said loading means further comprising a loading control means for controlling the operation of the first multiplexor for loading, i) the plurality of object coordinate registers with said X and Y coordinate pairs of said object, ii) the plurality of clip coordinate registers with said predetermind clip coordinates, and iii) the plurality of offset registers with predetermined X and Y offsets from said top and bottom clip coordinates, and from said right and left clip coordinates, said X and Y coordinate pairs of said object, said clip coordinates and said offset for use in calculations for performing clipping of the object prior to its display, wherein said predetermined X and Y offsets define a test window; e) comparison means coupled to said loading means for performing said comparisons between said X and Y coordinates of said object, said predetermined clip coordinates and said predetermined offsets; f) calculations means coupled to said offset register and said clip coordinate registers for calculating the borders of said test window relative to the borders of said clip window; g) a multiplexor coupled to said comparison means for selecting predetermined ones of said comparisons; h) at least one comparison register coupled to said multiplexor for storing the selected predetermined ones of said comparisons; i) comparison control means controling the operation of said comparison means, said multiplexor and said comparison register; j) status generation means coupled to said comparison register for generating said plurality of signals based upon certain of said selected predetermined ones of said comparisons which specify whether the X coordinate of each said X and Y coordinate pair is less than said predetermined left clip coordinate greater than said predetermined right clip coordinate, less than said predetermined left clip coordinate minus said X offset, greater than said predetermined right clip coordinatte plus said X offset, is representable in 15 bits, within said left clip coordinate and right clip coordinate, within said left clip coordinate minus said X offset and said right clip coordinate plus said X offset, and which specify whether the Y coordinate of each said X and Y coordinate pair is less than said predetermined bottom clip coordinate, greater than said predetermined top clip coordinate, less than said predetermined bottom clip coordinate minus said Y offset, greater than said predetermined top clip coordinate plus said Y offset, is representable in 15 bits, within said bottom clip coordinate and top clip coordinate, and within said bottom clip coordinate minus said Y offset and said top clip coordinate plus said Y offset.

Claim 2

An apparatus for performing comparisons between pairs of X and Y coordinates of an object to be displayed by a graphics subsystem, pairs of predetermined clip coordinates and pairs of predetermined offsets, and generating a plurality of signals representing the results of said comparisons, said object being one of a quadrilateral to be drawn and a block image to be moved, said apparatus having a clip window with predetermined top, bottom right and left clip coordinates, said apparatus comprising: a) a plurality of object coordinate registers; b) a plurality of clip coordinate register; c) a plurality of offset registers; d) loading means comprising a first multiplexor coupled to the plurality of object coordinate registers, the plurality of clip coordinate registers and the plurality of offset registers, said loading means further comprising a loading control means for controlling the operation of the first multiplexor for loading, i) the plurality of object coordinate registers with said X and Y coordinate pairs of said object, ii) the plurality of clip coordinate registers with said predetermind clip coordinates, and iii) the plurality of offset registers with predetermined X and Y offsets from said top and bottom clip coordinates, and from said right and left clip coordinates, said X and Y coordinate pairs of said object, said clip coordinates and said offset for use in calculations for performing clipping of the object prior to its display, wherein said predetermined X and Y offsets define a test window; e) comparison means coupled to said loading means for performing said comparisons between said X and Y coordinates of said object, said predetermined clip coordinates and said predetermined offsets; f) calculations means coupled to said offset register and said clip coordinate registers for calculating the borders of said test window relative to the borders of said clip window; g) a multiplexor coupled to said comparison means for selecting predetermined ones of said comparisons; h) at least one comparison register coupled to said multiplexor for storing the selected predetermined ones of said comparisons; i) comparison control means controling the operation of said comparison means, said multiplexor and said comparison register; j) status generation means coupled to said comparison register for generating said plurality of signals based upon certain of said selected predetermined ones of said comparisons which specify whether the X coordinate of each said X and Y coordinate pair is less than said predetermined left clip coordinate greater than said predetermined right clip coordinate, less than said predetermined left clip coordinate minus said X offset, greater than said predetermined right clip coordinatte plus said X offset, is representable in 15 bits, within said left clip coordinate and right clip coordinate, within said left clip coordinate minus said X offset and said right clip coordinate plus said X offset, and which specify whether the Y coordinate of each said X and Y coordinate pair is less than said predetermined bottom clip coordinate, greater than said predetermined top clip coordinate, less than said predetermined bottom clip coordinate minus said Y offset, greater than said predetermined top clip coordinate plus said Y offset, is representable in 15 bits, within said bottom clip coordinate and top clip coordinate, and within said bottom clip coordinate minus said Y offset and said top clip coordinate plus said Y offset.

Claim 9

A method for performing comparisons between pairs of X and Y coordinates of an object to be displayed by a graphics subsystem, pairs of predetermined clip coordinates and pairs of predetermined offsets, and generating a plurality of status signals representing the results of said comparisons, said object being one of a quadrilateral to be drawn and block image to be moved, said method employing a clip window with predetermined top, bottom, right and left clip coordinates , said method comprising the steps of: providing a plurality of object coordinate registers, a plurality of clip coordinate registers and a plurality of offset registers; loading i) a plurality of object coordinate registers with said X and Y coordinate pairs of said object, ii) a plurality of clip coordinate registers with said predetermined clip coordinates, and iii) a plurality of offset registers with said predetermined offsets; performing said comparisons between said X and Y coordinates of said object, said predetermined clip coordinate and said predetermined offsets with the coordinates and offsets respectively loaded into said plurality of object coordinate registers, plurality of clip coordinate registers and plurality of offset registers; determining the borders of said test window relative to the borders of said clip window from the offsets loaded into the offset register and the clip coordinates loaded into the clip coordinate register; selecting predetermined ones of said comparisons; storing the selected predetermined ones of said comparisons in at least one comparison register; generating a plurality of status based upon certain of said selected predetermined ones of said comparisons stored in at least one comparison register which specify whether the X coordinate of each said X and Y coordinate pair is less than said predetermined left clip coordinate, greater than said predetermined right clip coordinate, less than said predetermined left clip coordinate minus said X offset; greater than said predetermined right clip coordinate plus said X offset, is representable in 15 bits, within said left clip coordinate and right clip coordinate, within said left clip coordinate minus said X offset and said right clip coordinate plus said X offset, and which specify whether the Y coordinate of each said X and Y coordinate pair is less than said predetermined bottom clip coordinate, greater than said predetermined top clip coordinate, less than said predetermined bottom clip coordinate minus said Y offset, greater than said predetermined top clip coordinate plus said Y offset, is representable in 15 bits, within said bottom clip coordinate and top clip coordinate, and within said bottom clip coordinate minus said Y offset and said top clip coordinate plus said Y offset, set status signals output for generation of the display of the object.

Claim 10

A method for performing comparisons between pairs of X and Y coordinates of an object to be displayed by a graphics subsystem, pairs of predetermined clip coordinates and pairs of predetermined offsets, and generating a plurality of status signals representing the results of said comparisons, said object being one of a quadrilateral to be drawn and block image to be moved, said method employing a clip window with predetermined top, bottom, right and left clip coordinates , said method comprising the steps of: providing a plurality of object coordinate registers, a plurality of clip coordinate registers and a plurality of offset registers; loading i) a plurality of object coordinate registers with said X and Y coordinate pairs of said object, ii) a plurality of clip coordinate registers with said predetermined clip coordinates, and iii) a plurality of offset registers with said predetermined offsets; performing said comparisons between said X and Y coordinates of said object, said predetermined clip coordinate and said predetermined offsets with the coordinates and offsets respectively loaded into said plurality of object coordinate registers, plurality of clip coordinate registers and plurality of offset registers; determining the borders of said test window relative to the borders of said clip window from the offsets loaded into the offset register and the clip coordinates loaded into the clip coordinate register; selecting predetermined ones of said comparisons; storing the selected predetermined ones of said comparisons in at least one comparison register; generating a plurality of status based upon certain of said selected predetermined ones of said comparisons stored in at least one comparison register which specify whether the X coordinate of each said X and Y coordinate pair is less than said predetermined left clip coordinate, greater than said predetermined right clip coordinate, less than said predetermined left clip coordinate minus said X offset; greater than said predetermined right clip coordinate plus said X offset, is representable in 15 bits, within said left clip coordinate and right clip coordinate, within said left clip coordinate minus said X offset and said right clip coordinate plus said X offset, and which specify whether the Y coordinate of each said X and Y coordinate pair is less than said predetermined bottom clip coordinate, greater than said predetermined top clip coordinate, less than said predetermined bottom clip coordinate minus said Y offset, greater than said predetermined top clip coordinate plus said Y offset, is representable in 15 bits, within said bottom clip coordinate and top clip coordinate, and within said bottom clip coordinate minus said Y offset and said top clip coordinate plus said Y offset, set status signals output for generation of the display of the object.