| 摘要 |
PURPOSE:To discriminate a side unnecessary for smearing-away display within a display range and clarify a display range frame of vertexes to be projected, by calculating projection codes of start and end points of sides of a polygon defining a closed pattern. CONSTITUTION:Coordinate values xs, ys, xe, and ye of start and end points of a side to be discrminated and coordinate values XL, XR, YB, and YT defining the display range are given to a register 10 and a register 11 respectively from an external processor, and comparison operation on coordinate values of start and end points and coordinate values of the display range are executed in an ALU12. When the comparison operation is executed in each of steps 1-8, a positive or negative sign of the comparison result is inputted to a shift register 31 is order. When the operation is terminated up to the step 8, contents of the shift register 31 become a pair of projection codes for start and end points of the side. Parallel outputs of the shift register 31 are impressed to a decoder 32 which classifies the existence area of the side, and ''1'' is outputted to one of output lines 49-51. These outputs of the classification code are discriminated by a condition selector 30 in a sequencer 14. |
