hintz@quando.UUCP (Stefan Hintz) (04/11/90)
Can anybody tell me, how to make a circle out of Beziercurvesegments (each Bezier-segment is described by four points, (first and last point one the curve, and two other controlpoints)) I have experimented with two Beziercurvesegments but the result looked not as round as a circle. If anybody has an idea to this topic, or even knows how to define circles or arcs with Beziercurves, should post this to this newsgroup. Stefan Hintz, Dortmund, West Germany hintz@quando.quantum.de
robert@texas.sgi.com (Robert Skinner) (04/14/90)
In article <1419@quando.UUCP>, hintz@quando.UUCP (Stefan Hintz) writes: > Can anybody tell me, how to make a circle out of Beziercurvesegments > (each Bezier-segment is described by four points, (first and last point one > the curve, and two other controlpoints)) > I have experimented with two Beziercurvesegments but the result looked not as > round as a circle. > > If anybody has an idea to this topic, or even knows how to define circles or > arcs with Beziercurves, should post this to this newsgroup. > > > Stefan Hintz, Dortmund, West Germany > hintz@quando.quantum.de In "Computational Geometry for Design and Manufacture", by Faux and Pratt, page 134: for the arc r = cos(t) i + sin(t) j, 0 <= t <= pi/2, use r0 = i r1 = i + kj r2 = ki + j r3 = k where k = 4(sqrt(2) - 1)/3. The radius varies between 1 and 1.00027, the max deviation from the mean radius is +/-0.13% Robert Skinner robert@sgi.com "We are going to give a little something, a few little years more, to socialism, because socialism is defunct. It dies all by iself. The bad thing is that socialism, being a victim of its... Did I say socialism?" -Fidel Castro