This paper presents the results of a simulation study of the effect of rock size and shape on impact distance, defined as the distance from the base of a slope to the first point of impact. This study is based on new algorithms which take into account the geometric shape of the falling rocks based on rigid body dynamics. The introduction of rock shapes to rockfall simulations allows a more realistic interpretation of rockfall events, as the rock size influences both the contact kinematics and the post-impact dynamics. This, in turn, has a significant influence on the calculation of impact distance. Rock slope geometry also has a significant influence on the post-impact behaviour of falling rocks. The consideration of slope geometry is vital to any rockfall analysis. The combined effect of rock size and slope geometry adds an interesting dimension to the variation of final impact distance.