Summary To simulate data acquisition and for seismic data processing we need a 3-D velocity model. The data model has to be validated before it is ready for use in 3-D raytracing. Unfortunately, most current raytracing algorithms require the velocity model to be topologically correct. Simple models, which have single-valued surfaces are easy to build. However, the ones that require multivalued surfaces, (such as salt bodies) are very difficult to build. Until now, there are still two major problems: 1) it is difficult to reconstruct multi-valued surfaces from a given set of scattered data points and; 2) the embedding of the salt bodies into the surrounding sediments is still geometrically and topologically incorrect. The main contribution of this work is to efficiently build a closed surface from a given top and base of salt respectively, and make the embedded salt bodies consistent with the surrounding sediments.