SUMMARYWe present a method, which we have termed Relaxed Dual Complex (RDC), for generating geometric representations and computational models of polycrystals of arbitrary shape. The RDC method combines a first topological step, which defines an initial unrelaxed polycrystal geometry as the barycentric dual of an input triangulation of the solid, and a second relaxation step, in which the grain boundaries are relaxed by means of a gradient flow driven by grain boundary energy. The RDC method applies to arbitrary solids defined by means of a triangulation and, in this manner, it couples seamlessly to standard solid modelling engines. An additional appealing feature of the RDC method is that it generates a conforming tetrahedral mesh of the polycrystal that can be used as a basis for subsequent simulations. The RDC method also affords some control over the statistical properties of the polycrystal, including grain size, which provides a convenient device for matching experimental statistical data. The range, versatility, and performance of the RDC method have been demonstrated by means of selected examples.