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ABSTRACT3D mesh segmentation is a fundamental process for Digital Shape Reconstruction in a variety of applications including Reverse Engineering, Medical Imaging, etc. It is used to provide a high level representation of the raw 3D data which is required for CAD, CAM and CAE. In this paper, we present an exhaustive overview of 3D mesh segmentation methodologies examining their suitability for CAD models. In particular, a classification of the various methods is given based on their corresponding underlying fundamental methodology concept as well as on the distinct criteria and features used in the segmentation process.

Figure 1: Using our method, the human modeler simply drags-and-drops the shape primitives into approximate position; the system provides real-time precise geometric snapping feedback and infers geosemantic constraints between the primitives. (Total modeling time: one minute.) Abstract Modeling 3D objects from sketches is a process that requires several challenging problems including segmentation, recognition and reconstruction. Some of these tasks are harder for humans and some are harder for the machine. At the core of the problem lies the need for semantic understanding of the shape's geometry from the sketch. In this paper we propose a method to model 3D objects from sketches by utilizing humans specifically for semantic tasks that are very simple for humans and extremely difficult for the machine, while utilizing the machine for tasks that are harder for humans. The user assists recognition and segmentation by choosing and placing specific geometric primitives on the relevant parts of the sketch. The machine first snaps the primitive to the sketch by fitting its projection to the sketch lines, and then improves the model globally by inferring geosemantic constraints that link the different parts. The fitting occurs in real-time, allowing the user to be only as precise as needed to have a good starting configuration for this non-convex optimization problem. We evaluate the accessibility of our approach with a user study.

In this paper, a retrieval methodology for 3D articulated objects is presented that relies upon a graphbased object representation. The methodology is composed of a mesh segmentation stage which creates the Attributed Relation Graph (ARG) of the object along with a graph matching algorithm which matches two ARGs. The graph matching algorithm is based on the Earth Movers Distance (EMD) similarity measure calculated with a new ground distance assignment. The superior performance of the proposed retrieval methodology against state of the art approaches is shown by extensive experimentation that comprise the application of various geometric descriptors representing the components of the 3D objects that become the node attributes of the ARGs as well as alternative mesh segmentation approaches for the extraction of the object parts. The performance evaluation is addressed in both qualitative and quantitative terms.

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