| 摘要 |
<p>A source polygon (40) is clipped to a view window (30). The valid (i.e. potentially visible) edges (40a,40d,33a,35a) or portions of edges of the source polygon (40) and of the view window (30) boundary edges are permitted to be sequentially output for further processing, while determining the valid parts in a predetermined direction around the perimeter of the source polygon, without having to store (other than for a first entry point) the value of exit points from or entry points to the view window. Only an end point (e.g. 42b) of an edge (40a) of source polygon (40) is considered at a time so that a maximum of two intersection point determinations between the source polygon edge and view window boundary planes (11,13,15,17) outside of which the source polygon edge lies are required to ascertain if a portion of the source polygon edge is valid.</p> |
