Modes of vibration of a 3-D stick model. The first n! modes of an n-d model (in this case the first 6 modes of the 3-D model) represent rotation and translation and are not shown. Only odd modes are shown since, in this case, deformation of mode 2k is the same than mode 2k-1, except that it deforms orthogonal to mode 2k-1. If warping is omitted (upper row), local rotation is resulting in unwanted deformation.