公开(公告)号：DE3275669D1

公开(公告)日：1987-04-16

申请号：DE3275669

申请日：1982-12-30

Applicant: IBM

Inventor： RICHARDS JOHN PETER ,  BRESENHAM JACK E ,  GAY ADRIAN C

IPC: G06F3/153 ,  G06T11/00 ,  G09G5/00 ,  G09G5/32 ,  G09G5/36 ,  G09G5/393 ,  G09G5/42 ,  G09G1/16 ,  G09G1/06

Abstract: The invention concerns a graphics display system of the kind having a refresh raster display device, a line clipping mechanism for clipping line primitives for viewing in a selected rectangular viewport having horizontal and vertical edges parallel to the X and Y axes respectively of the display area of the display device, and a vector-to-raster converter for converting the clipped lines to patterns of discrete pels in a refresh buffer, the vector-to-raster converter including an incremental line drawing mechanism responsive to line information supplied by the clipping mechanism to draw the line starting at one endpoint and proceeding towards the other. In such a system, for at least some lines of a kind which have a first endpoint in the viewport and the second endpoint outside the viewport, the clipping mechanism is arranged to avoid calculating the intersection point of the line with the viewport edge intersected by the line, and the vector-to-raster converter is arranged to start the line drawing mechanism at the first endpoint and halt the line drawing mechanism when the currently generated coordinate along the display axis normal th the said viewport edge equals the coordinate of the viewport edge along the same axis.