Adaptive coarse-to-fine quantization for optimizing rate-distortion of progressive mesh compression

International audienceWe propose a new connectivity-based progressivecompression approach for triangle meshes. The keyidea is to adapt the quantization precision to the resolutionof each intermediate mesh so as to optimizethe rate-distortion trade-off. This adaptation is automaticallydetermined during the encoding processand the overhead is efficiently encoded using geometricalprediction techniques. We also introducean optimization of the geometry coding by usinga bijective discrete rotation. Results show that ourapproach delivers a better rate-distortion behaviorthan both connectivity-based and geometry-basedcompression state of the art method

Human Face Image Edge Detection Methods and Application

如何确定人脸特征并对这些特征进行有效的提取是非常关键而且复杂的。人脸边缘和轮廓是人脸非常重要的特征。该文研究了边缘检测的原理和各种算法,通过试验验证各种检测方法在人脸图像中对边缘的检测效果,讨论选用在不同阈值下检测的边缘,以及影响检测效果的因素。最后通过实例研究了人脸边缘检测在人脸检测和识别中的具体应用。How to define and extract the feature of human face is a key and complicated problem. The edge and contour of human face is one of important feature. This paper studies the theory of edge detection and different kinds of arithmetical methods. The experiment results are used to confirm the different methods which are employed to test the edge detection results of the human face image. It discusses the consequence of detection when the threshold is varying and the possible factors, which makes the different results. Finally, it studies the application of the edge detection in human face detection and recognition.福建省自然科学基金资助项目(A0310005);; 国家留学回国人员基金资助项目(K13003

Vlist and Ering: compact data structures for simplicial 2-complexes

Various data structures have been proposed for representing the connectivity of manifold triangle meshes. For example, the Extended Corner Table (ECT) stores V+6T references, where V and T respectively denote the vertex and triangle counts. ECT supports Random Access and Traversal (RAT) operators at Constant Amortized Time (CAT) cost. We propose two novel variations of ECT that also support RAT operations at CAT cost, but can be used to represent and process Simplicial 2-Complexes (S2Cs), which may represent star-connecting, non-orientable, and non-manifold triangulations along with dangling edges, which we call sticks. Vlist stores V+3T+3S+3(C+S-N) references, where S denotes the stick count, C denotes the number of edge-connected components and N denotes the number of star-connecting vertices. Ering stores 6T+3S+3(C+S-N) references, but has two advantages over Vlist: the Ering implementation of the operators is faster and is purely topological (i.e., it does not perform geometric queries). Vlist and Ering representations have two principal advantages over previously proposed representations for simplicial complexes: (1) Lower storage cost, at least for meshes with significantly more triangles than sticks, and (2) explicit support of side-respecting traversal operators which each walks from a corner on the face of a triangle t across an edge or a vertex of t, to a corner on a faces of a triangle or to an end of a stick that share a vertex with t, and this without ever piercing through the surface of a triangle.M.S

Progressive lossless compression of arbitrary simplicial complexes

Efficient algorithms for compressing geometric data have been widely developed in the recent years, but they are mainly designed for closed polyhedral surfaces which are manifold or “nearly manifold”. We propose here a progressive geometry compression scheme which can handle manifold models as well as “triangle soups ” and 3D tetrahedral meshes. The method is lossless when the decompression is complete which is extremely important in some domains such as medical or finite element. While most existing methods enumerate the vertices of the mesh in an order depending on the connectivity, we use a kd-tree technique [8] which does not depend on the connectivity. Then we compute a compatible sequence of meshes which can be encoded using edge expansion [14] and vertex split [24]. 1 The main contributions of this paper are: the idea of using the kd-tree encoding of the geometry to drive the construction of a sequence of meshes, an improved coding of the edge expansion and vertex split since the vertices to split are implicitly defined, a prediction scheme which reduces the code for simplices incident to the split vertex, and a new generalization of the edge expansion operation to tetrahedral meshes.