   } else {
                    threeLayer.removeMesh(lineTrails);
                }
            });
            gui.addColor(params, 'color').name('line color').onChange(function () {
                material.color.set(params.color);
                lineTrails.forEach(function (mesh) {
                    mesh.setSymbol(material);
                });
            });
            gui.add(params, 'opacity', 0, 1).onChange(function () {
                material.opacity = params.opacity;
                lineTra