Useful OpenSCAD Primitives

primitives.scad

module sector(radius, angle)
{
  fn = ($fn <= 0) ? 20 : $fn;

  polygon(
    [
      [0, 0],
      for (i = [0 : fn])
        let (a = i * angle / fn)
        [radius * cos(a), radius * sin(a)]
    ]);
}

module arc(radius1, radius2, angle)
{
  fn = ($fn <= 0) ? 20 : $fn;

  polygon(
    [
      for (i = [0 : fn])
        let (a = i * angle / fn)
        [radius1 * cos(a), radius1 * sin(a)],
      for (i = [0 : fn])
        let (a = (fn - i) * angle / fn)
        [radius2 * cos(a), radius2 * sin(a)]
    ]);
}

module cone(inclination, sweep, slice = [0, 200])
{
  rotate_extrude(angle = sweep)
  polygon(
    [
      [0, slice[0]],
      [slice[0] * sin(inclination), slice[0]],
      [slice[1] * sin(inclination), slice[1]],
      [0, slice[1]]
    ]);
}

$fn = 100;

sector(20, 150);

arc(50, 55, 220, $fn = 10);

difference()
{
  cone(25, 180, [40, 50]);
  
  translate([0, 0, 5])
  cone(25, 360, [30, 50], $fn = 15);
}