Chladni figures are wavy lines produced by scattered salt or sand on an elastic material of a given shape, possibly constrained at the edges or at a point in the center, and forced to vibrate with a violin bow. The modes of vibration can be identified because these small particles end up in the places of zero vibration, which happens at those parts of the surface that are stationary, namely at the nodes of vibration, where harmonics cancel. In the case of 3D images, the surfaces result from having three orthogonal harmonics that are periodic outside the domain shown.