Concave vertex of an object is an important parameter for analyzing an object’s shape. A new algorithm for searching concave vertex is proposed in this paper. The new algorithm requires tracking the border firstly,an...Concave vertex of an object is an important parameter for analyzing an object’s shape. A new algorithm for searching concave vertex is proposed in this paper. The new algorithm requires tracking the border firstly,and then uses sampling border to obtain coordinates sequence of discrete boundary points. Each sampling point of the discrete border is determined to be either concave or convex according to the value of vector product. Two inflexions can be searched by the change of concavo-convex trend. The region between two inflexions is defined as concave area. The values of distance are calculated between all boundary points on the concave area and a straight line connected by two inflexions. The boundary point corresponding to the greatest distances is max concave vertex,or the object’s concave vertex. Experimental results have proved that the new algorithm can extract the max concave vertexes of an object accurately and reliably.展开更多
LOD(Level of Details)层次细节模型的提出为三维复杂场景的实现提供了有力的技术支持。LOD简化通过顶点删除、边压缩、面片收缩操作来减少场景中的面片数,降低场景复杂度从而加快绘制速度。利用点删除操作进行模型简化时,需要对删除顶...LOD(Level of Details)层次细节模型的提出为三维复杂场景的实现提供了有力的技术支持。LOD简化通过顶点删除、边压缩、面片收缩操作来减少场景中的面片数,降低场景复杂度从而加快绘制速度。利用点删除操作进行模型简化时,需要对删除顶点后所形成的多边形"空洞"进行三角化再剖分,不同的剖分方法所形成的三角形网格质量是不同的。引入有限元网格剖分的概念,使用狄洛尼(Delaunay)三角剖分法则,提出对凸闭包自身三角化构建方法,对一个凸多边形进行了最优的剖分。所形成的三角形网格满足狄洛尼法则中的最大-最小角特性和空外接圆特性两个重要原则。展开更多
基金Supported by Natural Science Foundation of Guangdong Province (No.8451051501000501)the Science and Technology Projects of Guangdong Province (No.2009B-010800029)
文摘Concave vertex of an object is an important parameter for analyzing an object’s shape. A new algorithm for searching concave vertex is proposed in this paper. The new algorithm requires tracking the border firstly,and then uses sampling border to obtain coordinates sequence of discrete boundary points. Each sampling point of the discrete border is determined to be either concave or convex according to the value of vector product. Two inflexions can be searched by the change of concavo-convex trend. The region between two inflexions is defined as concave area. The values of distance are calculated between all boundary points on the concave area and a straight line connected by two inflexions. The boundary point corresponding to the greatest distances is max concave vertex,or the object’s concave vertex. Experimental results have proved that the new algorithm can extract the max concave vertexes of an object accurately and reliably.
文摘LOD(Level of Details)层次细节模型的提出为三维复杂场景的实现提供了有力的技术支持。LOD简化通过顶点删除、边压缩、面片收缩操作来减少场景中的面片数,降低场景复杂度从而加快绘制速度。利用点删除操作进行模型简化时,需要对删除顶点后所形成的多边形"空洞"进行三角化再剖分,不同的剖分方法所形成的三角形网格质量是不同的。引入有限元网格剖分的概念,使用狄洛尼(Delaunay)三角剖分法则,提出对凸闭包自身三角化构建方法,对一个凸多边形进行了最优的剖分。所形成的三角形网格满足狄洛尼法则中的最大-最小角特性和空外接圆特性两个重要原则。
