This paper describes an approach to construct unstructured tetrahedral and hexahedral meshes for a domain with multiple materials. In earlier works, we developed an octreebased isocontouring method to construct unstructured 3D meshes for a single-material domain. Based on this methodology, we introduce the notion of material change edge and use it to identify the interface between two or several materials. We then mesh each material region with conforming boundaries. Two kinds of surfaces, the boundary surface and the interface between two different material regions, are distinguished and meshed. Both material change edges and interior edges are analyzed to construct tetrahedral meshes, and interior grid points are analyzed for hexahedral mesh construction. Finally the edge-contraction and smoothing method is used to improve the quality of tetrahedral meshes, and a combination of pillowing, geometric flow and optimization techniques is used for hexahedral mesh quality improvement. The shrink set is defined automatically as the boundary of each material region. Several application results in different research fields are shown.
1. Human Brain Atlas
Mesh generation for the segmented brodmann brain atlas with about 40 areas or materials. In (b)-(e), only three areas (Area 19, 37, and 39) are shown. (a) - smooth shading of the constructed brain model, each color represents one material; (b) - a triangular mesh; (c) - a quadrilateral mesh; (d) - one cross-section of a hexahedral mesh; (e) - one cross-section of a tetrahedral mesh. Red windows show details.
2. Rice Dwarf Virus
Mesh generation for the segmented rice dwarf virus data (RDV). (a) - smooth shading of the segmented RDV model , each color represents four 1/3 trimers; (b) - a triangular mesh of one trimer consisting of three monomers; (c) - a quadrilateral mesh of one trimer; (d) - one cross-section of a hexahedral mesh; (e) - one cross-section of a tetrahedral mesh.