\documentclass{standalone} \usepackage{asymptote} \begin{document} \begin{asy}[width=10cm,height=10cm] import graph3; usepackage("amsfonts"); size3(200); currentprojection=orthographic(4,6,3); // parametrization real x(real t) {return cos(2pi*t);} real y(real t) {return sin(2pi*t);} real z(real t) {return 0.5*t;} real z0(real t) {return 0;} scale(true); // some parameters real delta = 0.01; real phix = 0.1; real phim = 6.7; // spiral path3 spiral1 = graph(x,y,z,0.9,1,operator ..); draw(spiral1,dotted); path3 spiral2 = graph(x,y,z,1,phim,operator ..); draw(spiral2,Arrow3); // blue circle draw(unitcircle3, blue); // orange segments pen sp = orange+1; draw(graph(x,y,z0,phix-delta,phix+delta,operator ..),sp); for(real i=1; i