docs: function() {
              if (!this.cachedBoundingBox) {
                  var minpoint, maxpoint;
                  var vertices = this.vertices;
                  var numvertices = vertices.length;
                  if (numvertices === 0) {
                      minpoint = new CSG.Vector3D(0, 0, 0);
                  } else {
                      minpoint = vertices[0].pos;
                  }
                  maxpoint = minpoint;
                  for (var i = 1; i < numvertices; i++) {
                      var point = vertices[i].pos;
                      minpoint = minpoint.min(point);
                      maxpoint = maxpoint.max(point);
                  }
                  this.cachedBoundingBox = [minpoint, maxpoint];
              }
              return this.cachedBoundingBox;
          }