A method of repairing a three dimensional surface mesh model to be watertight and manifold generally includes identifying a plurality of hole edges in the surface mesh model, selecting one of the hole edges, creating a cycle of hole edges that defines a hole in the surface mesh model, converting the cycle of hole edges into two or more cycles of exactly three edges each, and adding a triangular facet to the surface mesh model for each of the cycles of exactly three edges. The process may be repeated until the model is substantially watertight. Non-manifold vertices may be repaired by selecting a vertex of the model, identifying a number of independent cycles of triangular facets sharing the selected vertex, and redefining the selected vertex for at least all but one of the number of independent cycles. This process may be repeated until the model is manifold.