Modern computer graphics applications usually require high resolution object models for realistic rendering. However, it is expensive and difficult to deform such models in real time. In order to reduce the computatio...Modern computer graphics applications usually require high resolution object models for realistic rendering. However, it is expensive and difficult to deform such models in real time. In order to reduce the computational cost during deformations, a dense model is often manipulated through a simplified structure, called cage, which envelops the model. However, cages are usually built interactively by users, which is tedious and time-consuming. In this paper, we introduce a novel method that can build cages automatically for both 2D polygons and 3D triangular meshes. The method consists of two steps： 1） simplifying the input model with quadric error metrics and quadratic programming to build a coarse cage; 2） removing the self-intersections of the coarse cage with Delaunay partitions. With this new method, a user can build a cage to envelop an input model either entirely or partially with the approximate vertex number the user specifies. Experimental results show that, compared to other cage building methods with the same number of vertex, cages built by our method are more similar to the input models. Thus, the dense models can be manipulated with higher accuracy through our cages.展开更多
Objective:To clarify anatomy-related factors in the cervical spine with subsidence of titanium mesh cage (TMC) after one-level cervical corpectomy and fusion. The effect of the cervical posture, segmental curvature an...Objective:To clarify anatomy-related factors in the cervical spine with subsidence of titanium mesh cage (TMC) after one-level cervical corpectomy and fusion. The effect of the cervical posture, segmental curvature and endplate gradient on this postoperative phenomenon was evaluated. Methods: Between August 2003 and March 2006, a total of the 236 patients underwent one-level corpectomy and TMC fusion. Their radiological examinations were reviewed and clinical outcomes evaluated. Results: In the patients who were followed up for 12 months, TMC subsidence occurred in 54 (28.6%) cases. C6 corpectomy had a significant higher risk (26/60, 43.3%) for TMC subsidence, which was correlated with the variation of the gradient of the vertebral endplates against cervical levels. Although the clinical outcome was comparable with those in the literature, the patients may have subsidence-related problems such as neck-shoulder pain, neurological deterioration and instrumental failure. Conclusion: To decrease the incidence of subsidence, TMC design should be optimized to be in line with anatomic characteristics of the cervical spine.展开更多
基金Supported by the NSFC-Guangdong Joint Fund under Grant Nos. U0735001,U0835004,U0935004the National Basic Research 973 Program of China under Grant No. 2011CB302204
文摘Modern computer graphics applications usually require high resolution object models for realistic rendering. However, it is expensive and difficult to deform such models in real time. In order to reduce the computational cost during deformations, a dense model is often manipulated through a simplified structure, called cage, which envelops the model. However, cages are usually built interactively by users, which is tedious and time-consuming. In this paper, we introduce a novel method that can build cages automatically for both 2D polygons and 3D triangular meshes. The method consists of two steps： 1） simplifying the input model with quadric error metrics and quadratic programming to build a coarse cage; 2） removing the self-intersections of the coarse cage with Delaunay partitions. With this new method, a user can build a cage to envelop an input model either entirely or partially with the approximate vertex number the user specifies. Experimental results show that, compared to other cage building methods with the same number of vertex, cages built by our method are more similar to the input models. Thus, the dense models can be manipulated with higher accuracy through our cages.
文摘Objective:To clarify anatomy-related factors in the cervical spine with subsidence of titanium mesh cage (TMC) after one-level cervical corpectomy and fusion. The effect of the cervical posture, segmental curvature and endplate gradient on this postoperative phenomenon was evaluated. Methods: Between August 2003 and March 2006, a total of the 236 patients underwent one-level corpectomy and TMC fusion. Their radiological examinations were reviewed and clinical outcomes evaluated. Results: In the patients who were followed up for 12 months, TMC subsidence occurred in 54 (28.6%) cases. C6 corpectomy had a significant higher risk (26/60, 43.3%) for TMC subsidence, which was correlated with the variation of the gradient of the vertebral endplates against cervical levels. Although the clinical outcome was comparable with those in the literature, the patients may have subsidence-related problems such as neck-shoulder pain, neurological deterioration and instrumental failure. Conclusion: To decrease the incidence of subsidence, TMC design should be optimized to be in line with anatomic characteristics of the cervical spine.
