解答： 在 fillScene() 裡 var theta 後，替換程式為：

var cylinderGeo = new THREE.CylinderGeometry( 0.2, 0.2, cylLength, 32 );
for ( var i = 0; i < 4; i++ )
{
	var cylinder = new THREE.Mesh( cylinderGeo, cylinderMaterial );
	var x = (i < 2) ? -1 : 1;
	var z = (i % 2) ? -1 : 1;
	var rotationAxis = new THREE.Vector3(x,0,z);
	rotationAxis.normalize();
	cylinder.matrixAutoUpdate = false;
	cylinder.matrix.makeRotationAxis( rotationAxis, theta );
	scene.add( cylinder );
}