stlreader module can perform three tasks. The first one is to import a solid body represented by a STL file generated by a third-part software. Then, the corresponding level set function is generated, as shown in the top left of the right figure. The second one is to generate level set at each grid point corresponding to a hexahedron by providing coordinates at each vertex of the hexahedron, as shown in the bottom right of the right figure. The third one is to generate level set at each grid point for a special solid body which has zero thickness, such as shell with arbitrary shape by providing information of triangles which defines the shell in question, as shown in the top right and bottom left of the right figure. In all above tasks, the output of stlreader module are level sets corresponding to the solid body