Merging of intersecting triangulations for finite element modeling

Surface mesh generation over intersecting triangulations is a problem commo n to many branches of biomechanics. A new strategy for merging intersecting triangulations is described. The basis of the method is that object surfac es are represented as the zero-level iso-surface of the distance-to-surface function defined on a background grid. Thus, the triangulation of intersec ting objects reduces to the extraction of an iso-surface from an unstructur ed grid. In a first step, a regular background mesh is constructed. For eac h point of the background grid, the closest distance to the surface of each object is computed. Background points are then classified as external or i nternal by checking the direction of the surface normal at the closest loca tion and assigned a positive or negative distance, respectively. Finally, t he zero-level iso-surface is constructed. This is the final triangulation o f the intersecting objects. The overall accuracy is enhanced by adaptive re finement of the background grid elements. The resulting surface models are used as support surfaces to generate three-dimensional grids for finite ele ment analysis. The algorithms are demonstrated by merging arterial branches independently reconstructed from contrast-enhanced magnetic resonance imag es and by adding extra features such as vascular stents, Although the metho dology is presented in the context of finite element analysis of blood flow , the algorithms are general and can be applied in other areas as well. (C) 2001 Elsevier Science Ltd. All rights reserved.