A computer readable medium is provided embodying instructions executable by a processor to perform a method for generating a volumetric mask. The method includes providing a closed surface mesh, determining a discrete volume representation of the closed surface mesh, determining a temporary surface mask based on the closed surface mesh and a slice direction chosen from the discrete volume representation to produce a contour of the closed surface mesh for each slice of the discrete volume representation, and filling a surface defined by the contours to generate the volumetric mask.