In this paper, a case study is presented which is aimed at investigating the performance of several parallel versions of the POV--Ray raytracing package implemented on a workstation cluster using the MPI message passing library. Based on a manager/worker scheme, variants of workload partitioning and message scheduling strategies, in conjunction with different task granularities, are evaluated with respect to their runtime behaviour. The results indicate that dynamic, adaptive strategies are required to cope with both the unbalanced workload characteristics of the parallel raytracing application and the different computational capabilities of the machines in a workstation cluster environment. 1 Introduction Raytracing [9, 13, 24] is a widely used method for generating realistically looking images on a computer, and it is employed by many 3D modelling and animation systems for the final image rendering. The input to a raytracing algorithm is the scene -- the description of the geometry...