Abstract: Existing circular window clipping algorithms are inefficient for many complex
real-life applications like intelligent CAD and graphics recognition/understanding systems, due to
their large number of graphical primitives, complicated geometrical constraints and real-time
interaction requirements. This paper presents a fast line clipping algorithm against circular
windows. The proposed algorithm is composed of three parts: adaptive identification of invisible
lines based on tangent lines separation, fast identification of visible lines based on polygons
cutting, and fast line-arc intersections generation based on predefined tables retrieval.
Experimental results demonstrate that the proposed algorithm greatly reduces the computational
cost to clip lines by adaptive line-circle situation analysis and replacement of time-consuming
operations with simpler ones.

Key words: table-based retrieval, circular window, fast clipping, adaptive identification