title: Linear & rotational extrude at the same time
body: <p>I'm trying to draw this (hollow) shape:</p>
  
  <p><img src="https://i.stack.imgur.com/OIFqV.png" alt="funky_shape"></p>
  
  <p>The circles are actually different diameters, and I am wanting to neck down the middle of the connecting tube like that (but its not a requirement).  I can fake the shape by drawing it segment-by-segment, but I have problems necking it down, and it doesn't feel like how OpenSCAD wants it done (namely the hour-long CSG generation).  Any better ways to do this? <img src="https://i.stack.imgur.com/hFzDn.png" alt="rendered shape">:</p>
  
  <pre><code>for(i = [0:180]) {
      rotate([0,i,0])
      translate([26,0,0])
      difference() {
          cylinder(r=10 + (0.083 * i),h=.1);
          cylinder(r=8 + (0.083 * i),h=.1);
      }
  }
  </code></pre>