code: function linear_extrude(p,s) {
     //console.log("linear_extrude() not yet implemented");
     //return;
     var h = 1, off = 0, /* convexity = 10,*/ twist = 0, slices = 10;
     if(p.height) h = p.height;
     //if(p.convexity) convexity = p.convexity;      // abandoned
     if(p.twist) twist = p.twist;
     if(p.slices) slices = p.slices;
     var o = s.extrude({offset:[0,0,h], twistangle:twist, twiststeps:slices});
     if(p.center==true) {
        var b = new Array;
        b = o.getBounds();      // b[0] = min, b[1] = max
        off = b[1].plus(b[0]);
        off = off.times(-0.5);
        o = o.translate(off);
     }
     return o;
  }
docs: -- 2D to 3D primitives (OpenSCAD like notion)