spring geometry

// spring geometry
// by @_sorceress

C = 8.00;    // number of coils in the spring
L = 8.00;    // length of the spring (this is what you want to vary)
R = 1.00;    // radius of the spring
G = 0.15;    // gauge of spring wire

ures = 10*C; // steps along spring wire
vres = 10;   // steps around spring wire

for(v=0; v<vres; v++) {
  vscale = 2*PI*v/vres;
  gr = G * cos(vscale) + R;
  gz = G * sin(vscale);
  for(u=0; u<ures; u++) {
    uscale = u/ures;
    x = gr * cos(2*PI*C*uscale);
    y = gr * sin(2*PI*C*uscale);
    z = gz + L * uscale;
    // Output vector (x,y,z) which you can use in a vertex array, or whatever
  }
}