Abstract: A method and apparatus for detecting operator selection of a graphics object prior to rasterization and pixel generation for that object. The method divides the screen into regions and analyzes successive end points and vectors based upon their region to determine trivial picks and trivial no picks. Non-trivial conditions are analyzed by determining the position of the line segment being processed relative to two selected pick window vertices. Apparatus for implementing pick detect is provided that accomplishes pick detect as part of graphics pipeline processing. In the trivial pick or no pick cases, the apparatus does not slow pipeline operation, while in a non-trivial case, extra processing cycles are required.

Abstract: Method and apparatus for setting up a graphics vector generator. Computing values representative of difference functions between delta Y values and delta X values for a vector to be drawn; storing such functions; and storing a sign of said difference functions for controlling X, Y, swap and multiplex operations. An X, Y, swap for swapping x values and Y values in response to said sign storage to present a larger of an X function or a Y function to a control means for controlling a number of iterations in generation of a vector and iteration counter for controlling a number of iterations in generation of a vector.

Abstract: A method for clipping a line segment boundary-defined area against a limiting plane is disclosed for use in a computer graphics display system wherein graphics figures are represented by random sets of polylines definitive of line segment boundary-defined areas. Pursuant to the clipping method, once two intersection points are generated against one plane, the points are connected to form an edge of the new clipped boundary-defined area. The order of intersection point connection is irrelevant to the invention and the method can accomodate discontinuously presented data as readily as continuously presented data. Implementing the method essentially requires only one register to store the first intersection point and a flag register to indicate the status of the present clip point, i.e., whether the clipped point is the first or second of two points to be paired.

Abstract: A system for generating multiple pixels in a single machine cycle employs a plurality of parallel vector generators. Each of the parallel generators is initialized with an error term which is calcualted in accordance with Bresenham's algorithm. The signs of these error terms are then used to determine the region within the first octant of the coordinate system which contains the function for which the pixels are to be generated. The region data, in turn, determine two selectable values for an increment which is to be added to a running error term for each of the parallel generators as multiple pixels are simultaneously generated. The choice of the two possible values to be added to the error term is dependent upon the sign of the error term itself. The sign of the running error term for each vector generator is utilized to form a sequence of binary data which represents the incremental changes in the pixel positions as the pixels are being generated.