公开(公告)号：DE3854223T2

公开(公告)日：1996-02-29

申请号：DE3854223

申请日：1988-09-19

Applicant: IBM

Inventor： GONZALEZ-LOPEZ JORGE ,  CHAO-CHU BOB

IPC: G06T15/40 ,  G09B9/30

Abstract: Polygon vertex data is processed in three steps to create a graphics display without hidden lines and without gaps in the displayed lines. The technique permits the processing of triangles rather than polygons having four or more sides. In the first step, the Z values for the display points for the visible edges of the polygons are identified and assigned a reserved value ZCLOSE in a frame buffer. In the second step, the polygons are tessellated into triangles and the Z values for the display points on the triangles are computed and each depth buffer storage location is updated so as to contain the value of points closest to the viewpoint while the frame buffer is written with a background colour. In the final step, the Z values for the display points of the polygon edges are again computed and compared with the corresponding Z values in the depth buffer. The depth buffer is updated with the computed values if the stored value is equal to ZCLOSE or if the computed value represents a position closer to the viewpoint than the stored value and the frame buffer is then written with a foreground colour for the display point in question.

公开(公告)号：DE3854223D1

公开(公告)日：1995-08-31

申请号：DE3854223

申请日：1988-09-19

Applicant: IBM

Inventor： GONZALEZ-LOPEZ JORGE ,  CHAO-CHU BOB

IPC: G06T15/40 ,  G09B9/30

Abstract: Polygon vertex data is processed in three steps to create a graphics display without hidden lines and without gaps in the displayed lines. The technique permits the processing of triangles rather than polygons having four or more sides. In the first step, the Z values for the display points for the visible edges of the polygons are identified and assigned a reserved value ZCLOSE in a frame buffer. In the second step, the polygons are tessellated into triangles and the Z values for the display points on the triangles are computed and each depth buffer storage location is updated so as to contain the value of points closest to the viewpoint while the frame buffer is written with a background colour. In the final step, the Z values for the display points of the polygon edges are again computed and compared with the corresponding Z values in the depth buffer. The depth buffer is updated with the computed values if the stored value is equal to ZCLOSE or if the computed value represents a position closer to the viewpoint than the stored value and the frame buffer is then written with a foreground colour for the display point in question.