docs: function(orthobasis) {
              var points2d = this.vertices.map(function(vertex) {
                  return orthobasis.to2D(vertex.pos);
              });
              var result = CAG.fromPointsNoCheck(points2d);
              var area = result.area();
              if (Math.abs(area) < 1e-5) {
                  // the polygon was perpendicular to the orthnormal plane. The resulting 2D polygon would be degenerate
                  // return an empty area instead:
                  result = new CAG();
              } else if (area < 0) {
                  result = result.flipped();
              }
              return result;
          }