A novel method for boundary constrained tetrahedral mesh generation is proposed based on Advancing Front Technique(AFT)and conforming Delaunay triangulation.Given a triangulated surface mesh,AFT is firstly applied to ...A novel method for boundary constrained tetrahedral mesh generation is proposed based on Advancing Front Technique(AFT)and conforming Delaunay triangulation.Given a triangulated surface mesh,AFT is firstly applied to mesh several layers of elements adjacent to the boundary.The rest of the domain is then meshed by the conforming Delaunay triangulation.The non-conformal interface between two parts of meshes are adjusted.Mesh refinement and mesh optimization are then preformed to obtain a more reasonable-sized mesh with better quality.Robustness and quality of the proposed method is shown.Convergence proof of each stage as well as the whole algorithm is provided.Various numerical examples are included as well as the quality of the meshes.展开更多
A quasi non-overlapping hybrid scheme that combines the finite-difference time-domain(FDTD)method and the finite-element time-domain(FETD)method with nonconforming meshes is developed for time-domain solutions of Maxw...A quasi non-overlapping hybrid scheme that combines the finite-difference time-domain(FDTD)method and the finite-element time-domain(FETD)method with nonconforming meshes is developed for time-domain solutions of Maxwell’s equations.The FETD method uses mixed-order basis functions for electric and magnetic fields,while the FDTD method uses the traditional Yee’s grid;the two methods are joined by a buffer zone with the FETD method and the discontinuous Galerkin method is used for the domain decomposition in the FETD subdomains.The main features of this technique is that it allows non-conforming meshes and an arbitrary numbers of FETD and FDTD subdomains.The hybrid method is completely stable for the time steps up to the stability limit for the FDTD method and FETD method.Numerical results demonstrate the validity of this technique.展开更多
This paper gives a method of quantifying small visual differences between 3D mesh models with conforming topology, based on the theory of strain fields. Strain field is a geometric quantity in elasticity which is used...This paper gives a method of quantifying small visual differences between 3D mesh models with conforming topology, based on the theory of strain fields. Strain field is a geometric quantity in elasticity which is used to describe the deformation of elastomer. In this paper we consider the 3D models as objects with elasticity. The further demonstrations are provided： the first is intended to give the reader a visual impression of how our measure works in practice; and the second is to give readers a visual impression of how our measure works in evaluating filter algorithms. Our experiments show that our difference estimates are well correlated with human perception of differences. This work has applications in the evaluation of 3D mesh watermarking, 3D mesh compression reconstruction, and 3D mesh filtering.展开更多
A novel construction algorithm is presented to generate a conforming Voronoi mesh for any planar straight line graph (PSLG). It is also extended to tesselate multiple-intersected PSLGs. All the algorithms are guarante...A novel construction algorithm is presented to generate a conforming Voronoi mesh for any planar straight line graph (PSLG). It is also extended to tesselate multiple-intersected PSLGs. All the algorithms are guaranteed to converge. Examples are given to illustrate its efficiency.展开更多
提出了一种基于三角面元数据生成涂层目标时域有限差分(finite-difference time domain,FDTD)共形网格的方法。通过将原目标中各三角面元的顶点沿曲面在该点处的法线方向内移(内涂层)或外移(外涂层)所需的厚度,得到一组关于涂层的三角...提出了一种基于三角面元数据生成涂层目标时域有限差分(finite-difference time domain,FDTD)共形网格的方法。通过将原目标中各三角面元的顶点沿曲面在该点处的法线方向内移(内涂层)或外移(外涂层)所需的厚度,得到一组关于涂层的三角面元数据。其中曲面上各顶点处的法线方向近似等于包围该顶点的各三角面元的单位法向的矢量和。对于局部涂敷的情况,可根据需要只将涂敷部分所包含的三角面元顶点进行相应的移动,而其余顶点的位置保持不变。利用投影求交法,由原目标的三角面元数据和新生成的涂层三角面元数据即可得到共形FDTD计算所需要的共形网格参数。数值结果验证了方法的正确性和有效性。展开更多
Cultural relics line graphic serves as a crucial form of traditional artifact information documentation,which is a simple and intuitive product with low cost of displaying compared with 3D models.Dimensionality reduct...Cultural relics line graphic serves as a crucial form of traditional artifact information documentation,which is a simple and intuitive product with low cost of displaying compared with 3D models.Dimensionality reduction is undoubtedly necessary for line drawings.However,most existing methods for artifact drawing rely on the principles of orthographic projection that always cannot avoid angle occlusion and data overlapping while the surface of cultural relics is complex.Therefore,conformal mapping was introduced as a dimensionality reduction way to compensate for the limitation of orthographic projection.Based on the given criteria for assessing surface complexity,this paper proposed a three-dimensional feature guideline extraction method for complex cultural relic surfaces.A 2D and 3D combined factor that measured the importance of points on describing surface features,vertex weight,was designed.Then the selection threshold for feature guideline extraction was determined based on the differences between vertex weight and shape index distributions.The feasibility and stability were verified through experiments conducted on real cultural relic surface data.Results demonstrated the ability of the method to address the challenges associated with the automatic generation of line drawings for complex surfaces.The extraction method and the obtained results will be useful for line graphic drawing,displaying and propaganda of cultural relics.展开更多
基金Singapore MOE ARC 29/07 T207B2202,MOE RG 59/08 M52110092,NRF 2007IDM-IDM 002-010Natural Science Foundation of China 10971226 and 91130013,973 Program of China 2009CB723800the foundation of State Key Laboratory of Aerodynamics.
文摘A novel method for boundary constrained tetrahedral mesh generation is proposed based on Advancing Front Technique(AFT)and conforming Delaunay triangulation.Given a triangulated surface mesh,AFT is firstly applied to mesh several layers of elements adjacent to the boundary.The rest of the domain is then meshed by the conforming Delaunay triangulation.The non-conformal interface between two parts of meshes are adjusted.Mesh refinement and mesh optimization are then preformed to obtain a more reasonable-sized mesh with better quality.Robustness and quality of the proposed method is shown.Convergence proof of each stage as well as the whole algorithm is provided.Various numerical examples are included as well as the quality of the meshes.
文摘A quasi non-overlapping hybrid scheme that combines the finite-difference time-domain(FDTD)method and the finite-element time-domain(FETD)method with nonconforming meshes is developed for time-domain solutions of Maxwell’s equations.The FETD method uses mixed-order basis functions for electric and magnetic fields,while the FDTD method uses the traditional Yee’s grid;the two methods are joined by a buffer zone with the FETD method and the discontinuous Galerkin method is used for the domain decomposition in the FETD subdomains.The main features of this technique is that it allows non-conforming meshes and an arbitrary numbers of FETD and FDTD subdomains.The hybrid method is completely stable for the time steps up to the stability limit for the FDTD method and FETD method.Numerical results demonstrate the validity of this technique.
基金supported by the National Basic Research 973 Program of China under Grant No.2006CB303104the National Natural Science Foundation of China under Grant No.60673004an EPSRC Travel Grant.
文摘This paper gives a method of quantifying small visual differences between 3D mesh models with conforming topology, based on the theory of strain fields. Strain field is a geometric quantity in elasticity which is used to describe the deformation of elastomer. In this paper we consider the 3D models as objects with elasticity. The further demonstrations are provided： the first is intended to give the reader a visual impression of how our measure works in practice; and the second is to give readers a visual impression of how our measure works in evaluating filter algorithms. Our experiments show that our difference estimates are well correlated with human perception of differences. This work has applications in the evaluation of 3D mesh watermarking, 3D mesh compression reconstruction, and 3D mesh filtering.
基金Supported by the Science Technology Development Program of Beijing Municipal Education Commission (KM200510011004)
文摘A novel construction algorithm is presented to generate a conforming Voronoi mesh for any planar straight line graph (PSLG). It is also extended to tesselate multiple-intersected PSLGs. All the algorithms are guaranteed to converge. Examples are given to illustrate its efficiency.
文摘提出了一种基于三角面元数据生成涂层目标时域有限差分(finite-difference time domain,FDTD)共形网格的方法。通过将原目标中各三角面元的顶点沿曲面在该点处的法线方向内移(内涂层)或外移(外涂层)所需的厚度,得到一组关于涂层的三角面元数据。其中曲面上各顶点处的法线方向近似等于包围该顶点的各三角面元的单位法向的矢量和。对于局部涂敷的情况,可根据需要只将涂敷部分所包含的三角面元顶点进行相应的移动,而其余顶点的位置保持不变。利用投影求交法,由原目标的三角面元数据和新生成的涂层三角面元数据即可得到共形FDTD计算所需要的共形网格参数。数值结果验证了方法的正确性和有效性。
基金National Natural Science Foundation of China(Nos.42071444,42101444)。
文摘Cultural relics line graphic serves as a crucial form of traditional artifact information documentation,which is a simple and intuitive product with low cost of displaying compared with 3D models.Dimensionality reduction is undoubtedly necessary for line drawings.However,most existing methods for artifact drawing rely on the principles of orthographic projection that always cannot avoid angle occlusion and data overlapping while the surface of cultural relics is complex.Therefore,conformal mapping was introduced as a dimensionality reduction way to compensate for the limitation of orthographic projection.Based on the given criteria for assessing surface complexity,this paper proposed a three-dimensional feature guideline extraction method for complex cultural relic surfaces.A 2D and 3D combined factor that measured the importance of points on describing surface features,vertex weight,was designed.Then the selection threshold for feature guideline extraction was determined based on the differences between vertex weight and shape index distributions.The feasibility and stability were verified through experiments conducted on real cultural relic surface data.Results demonstrated the ability of the method to address the challenges associated with the automatic generation of line drawings for complex surfaces.The extraction method and the obtained results will be useful for line graphic drawing,displaying and propaganda of cultural relics.
