Constant Curvature Space Curves

with torsion function tau(s) = a0 + a1*sin(s) + a2*sin(2s) + a3*sin(3s)

a0 = 0 implies normal symmetry planes at s = n*pi, hence closed curves in 1-parameter families. Vary a1, a2 or a3 and watch kappa adjusted to nearby closing values.
- Very flat zeros imply very stationary osculating circles, the curves look almost as made of circle arcs.
- Very flat extrema result in curves which look as made of pieces of helices connected by circle arcs, especially if a0 = 0.
- a0 > 0, a2 = 0 allows more complicated curves, but more difficult to find. The curves have symmetry normals and the program tries to adjust a0 so that these are coplanar and hence pass through one point. The user has to vary other parameters to find closed examples.