Update for space curescurves
curvature[f_] := With[{d1 = D[f, u], d2 = D[f, {u, 2}]}, Norm[Cross[d1, d2]] / Norm[d1]^3 // Simplify] loxodromes[a_, b_] := { 2 a E^(b u) Cos[u], 2 a E^(b u) Sin[u], a^2 E^(2 b u) - 1 } / (1 + a^2 E^(2 b u)) cur = curvature[loxodromes[1, 0.1]]; plo = Plot[cur, {u, -4 Pi, 4 Pi}, PlotRange -> All] range = Last[PlotRange /. AbsoluteOptions[plo, PlotRange]]; Show[ ParametricPlot3D[loxodromes[1, 0.1], {u, -4 Pi, 4 Pi}, ColorFunction -> Function[{x, y, z, u, v}, ColorData["Rainbow"][Rescale[cur, range]]], ColorFunctionScaling -> False, PlotStyle -> Thickness[0.01]], Graphics3D[{Opacity[0.2], Sphere[]}], ImageSize -> 500 ]500] 
