Show/hide a dat.GUI form
dat.GUI.prototype.toggleHide = function() {
if(this.domElement.hasAttribute("hidden")) {
this.domElement.removeAttribute("hidden");
} else {
this.domElement.setAttribute("hidden", true);
}
};
dat.GUI.prototype.hide = function() {
this.domElement.setAttribute("hidden", true);
};
dat.GUI.prototype.show = function() {
this.domElement.removeAttribute("hidden");
};