In this study we use a numerical model to simulate the development of spiral inclusion trails according to both the rotation and non-rotation models of spiral development. We present a series of twenty-two Quicktime movies, and related figures, to illustrate both the 3D development of spiral inclusion trails, and the 3D geometry of the completed simulations. We also conducted simulations to assess the effect on spiral geometry of varying the following factors: degree of coupling between sphere and matrix, growth rate of sphere, angle between initial foliation and shear plane, and ratio of simple shear to pure shear. The simulations illustrate the similar 3D geometry of spirals produced by both the rotation and non-rotation models. Various inclusion trail patterns commonly observed in thin section, including clam shell and millipede microstructures, are explained in terms of 2D sections through the 3D spiral geometry.