Koenderink and van Doorn introduced aspect graphs as a way of representing 3-D shape for object recognition. The set of viewpoints on the gaussian sphere is partitioned into regions such that in each region, the qualitative structure of the line drawing remains the same. The viewing data of an object is the partition of the gaussian sphere together with a representative line drawings for each region of the partition. In this paper we present an algorithm to compute the viewing data of polyhedral objects. In the course of presenting the algorithm, we provide a full catalog of the visual events that occur for this type of objects.