Graphics Gems III (IBM Version)

IV.5

JOINING TWO LINES WITH A CIRCULAR ARC FILLET

Robert D. Miller,     East Lansing, Michigan

Publisher Summary

This chapter presents an algorithm to find the beginning angle and the angle subtended by the arc and the direction in which the arc is drawn. The method described in the chapter involves finding the equation in the form ax + by + c = 0 for each line. The center of the constructed arc, Pc, must lie at a distance r from both lines. The signed distance d₁ is determined from I₁ to the midpoint of I₂ and d₂ from I₂ to the midpoint of I₁. The midpoints are used because, in practice, one point may be common to both lines. The signs of d1 and d 2 determine on which sides of the respective lines the arc center Pc resides. The signed distances ...