Molecular geometric properties, such as volume, exposed surface area, and occurrence of internal cavities, are important inputs to many applications in molecular modeling. In this work we describe a very general and highly efficient approach for the accurate computation of such properties, which is applicable to arbitrary molecular surface models. The technique relies on a high performance ray casting framework that can be easily adapted to the computation of further quantities of interest at interactive speed, even for huge models. Keywords-ray tracing; surface area; volume;