The geometry process tool in the Lesimx consists of the following modules. It can create a solid body with an arbitrary shape and represent it using a level set function. It can also import an arbitrary solid body represented by a STL file generated by a third part software, then represented it by a level set function. With an arbitrary solid body represented by a level set function in a computational domain. The information at a grid point such as perpendicular distance to the solid surface, the normal vector and the its relative location with respect to the solid surface is given. All this information provides the concerned geometry parameters to implement an immersed boundary method.