This paper presents a density control based adaptive hexahedral mesh generation algorithm for three dimensional models. To improve the mesh quality of hexahedral elements, a set of improved 27-refinement templates is proposed and the refinement modes of these templates are given. A set of effective refinement templates for 8-refinement based mesh generation algorithm is employed. The corresponding date structure and the procedures for realization of the algorithm are also presented. A buffer layer is inserted on the concave domains to resolve the propagation problems. Finally, the effectiveness and robustness of the algorithm are demonstrated by using several examples. 
Incorporating improved refinement techniques for a grid-based geometrically-adaptive hexahedral mesh generation algorithm