Stable haptic interaction based on adaptive hierarchical shape matching

In this paper, we present a framework allowing users to interact with geometrically complex3 D deformable objects using(multiple) haptic devices based on an extended shape matching approach. There are two major challenges for haptic-enabled interaction using the shape matching method. The first is how to obtain a rapid deformation propagation when a large number of shape matching clusters exist. The second is how to robustly handle the collision response when the haptic interaction point hits the particlesampled deformable volume. Our framework extends existing multi-resolution shape matching methods,providing an improved energy convergence rate. This is achieved by using adaptive integration strategies to avoid insignificant shape matching iterations during the simulation. Furthermore, we present a new mechanism called stable constraint particle coupling which ensures consistent deformable behavior during haptic interaction. As demonstrated in our experimental results, the proposed method provides natural and smooth haptic rendering as well as efficient yet stable deformable simulation of complex models in real time.

Part-level 3-D object classification with improved interpretation tree

For classifying unknown 3-D objects into a set of predetermined object classes, a part-level object classification method based on the improved interpretation tree is presented. The part-level representation is implemented, which enables a more compact shape description of 3-D objects. The proposed classification method consists of two key processing stages： the improved constrained search on an interpretation tree and the following shape similarity measure computation. By the classification method, both whole match and partial match with shape similarity ranks are achieved; especially, focus match can be accomplished, where different key parts may be labeled and all the matched models containing corresponding key parts may be obtained. A series of experiments show the effectiveness of the presented 3-D object classification method.

Automatic 3D Shape Co-Segmentation Using Spectral Graph Method

Co-analyzing a set of 3D shapes is a challenging task considering a large geometrical variability of the shapes. To address this challenge, this paper proposes a new automatic 3D shape co-segmentation algorithm by using spectral graph method. Our method firstly represents input shapes as a set of weighted graphs and extracts multiple geometric features to measure the similarities of faces in each individual shape. Secondly all graphs are embedded into the spectral domain to find meaningful correspondences across the set, After that we build a joint weighted matrix for the graph set and then apply normalized cut criterion to find optimal co-segmentation of the input shapes. Finally we evaluate our approach on different categories of 3D shapes, and the experimental results demonstrate that our method can accurately co-segment a wide variety of shapes, which may have different poses and significant topology changes.

TransHist:Occlusion-robust shape detection in cluttered images

Shape matching plays an important role in various computer vision and graphics applications such as shape retrieval, object detection, image editing,image retrieval, etc. However, detecting shapes in cluttered images is still quite challenging due to the incomplete edges and changing perspective. In this paper, we propose a novel approach that can efficiently identify a queried shape in a cluttered image. The core idea is to acquire the transformation from the queried shape to the cluttered image by summarising all pointto-point transformations between the queried shape and the image. To do so, we adopt a point-based shape descriptor, the pyramid of arc-length descriptor(PAD),to identify point pairs between the queried shape and the image having similar local shapes. We further calculate the transformations between the identified point pairs based on PAD. Finally, we summarise all transformations in a 4 D transformation histogram and search for the main cluster. Our method can handle both closed shapes and open curves, and is resistant to partial occlusions. Experiments show that our method can robustly detect shapes in images in the presence of partial occlusions, fragile edges, and cluttered backgrounds.

An anisotropic Chebyshev descriptor and its optimization for deformable shape correspondence

Shape descriptors have recently gained popularity in shape matching,statistical shape modeling,etc.Their discriminative ability and efficiency play a decisive role in these tasks.In this paper,we first propose a novel handcrafted anisotropic spectral descriptor using Chebyshev polynomials,called the anisotropic Chebyshev descriptor(ACD);it can effectively capture shape features in multiple directions.The ACD inherits many good characteristics of spectral descriptors,such as being intrinsic,robust to changes in surface discretization,etc.Furthermore,due to the orthogonality of Chebyshev polynomials,the ACD is compact and can disambiguate intrinsic symmetry sinces everal directions are considered.To improve the ACD’s discrimination ability,we construct a Chebyshev spectral manifold convolutional neural network(CSMCNN)that optimizes the ACD and produces a learned ACD.Our experimental results show that the ACD outperforms existing state-of-the-art handcrafted descriptors.The combination of the ACD and the CSMCNN is better than other state-of-the-art learned descriptors in terms of discrimination,efficiency,and robustness to changes in shape resolution and discretization.

Inexact graph matching using a hierarchy of matching processes

Inexact graph matching algorithms have proved to be useful in many applications,such as character recognition,shape analysis,and image analysis. Inexact graph matching is,however,inherently an NP-hard problem with exponential computational complexity. Much of the previous research has focused on solving this problem using heuristics or estimations. Unfortunately,many of these techniques do not guarantee that an optimal solution will be found. It is the aim of the proposed algorithm to reduce the complexity of the inexact graph matching process,while still producing an optimal solution for a known application. This is achieved by greatly simplifying each individual matching process,and compensating for lost robustness by producing a hierarchy of matching processes. The creation of each matching process in the hierarchy is driven by an application-specific criterion that operates at the subgraph scale. To our knowledge,this problem has never before been approached in this manner. Results show that the proposed algorithm is faster than two existing methods based on graph edit operations.The proposed algorithm produces accurate results in terms of matching graphs,and shows promise for the application of shape matching. The proposed algorithm can easily be extended to produce a sub-optimal solution if required.

A facial reconstruction method based on new mesh deformation techniques

This article presents a new numerical method for facial reconstruction.The problem is the following:given a dry skull,reconstruct a virtual face that would help in the identification of the subject.The approach combines classical features as the use of a skulls/faces database and more original aspects:(1)an original shape matching method is used to link the unknown skull to the database templates;(2)the final face is seen as an elastic 3D mask that is deformed and adapted onto the unknown skull.In this method,the skull is considered as a whole surface and not restricted to some anatomical landmarks,allowing a dense description of the skull/face relationship.Also,the approach is fully automated.Various results are presented to show its efficiency.

Approximating interior bounded box of 3D character mesh model based on its skeleton and symmetry

Purpose – In the process of robot shell design, it is necessary to match the shape of the input 3D originalcharacter mesh model and robot endoskeleton, in order to make the input model fit for robot and avoidcollision. So, the purpose of this paper is to find an object of reference, which can be used for the process ofshape matching.Design/methodology/approach – In this work, the authors propose an interior bounded box (IBB)approach that derives from oriented bounding box (OBB). This kind of box is inside the closed mesh model.At the same time, it has maximum volume which is aligned with the object axis but is enclosed by all the meshvertices. Based on the IBB of input mesh model and the OBB of robot endoskeleton, the authors can completethe process of shape matching. In this paper, the authors use an evolutionary algorithm, covariance matrixadaptation evolution strategy (CMA-ES), to approximate the IBB based on skeleton and symmetry of inputcharacter mesh model.Findings – Based on the evolutionary algorithm CMA-ES, the optimal position and scale informationof IBB can be found. The authors can obtain satisfactory IBB result after this optimization process.The output IBB has maximum volume and is enveloped by the input character mesh model as well.Originality/value – To the best knowledge of the authors, the IBB is first proposed and used in the field ofrobot shell design. Taking advantage of the IBB, people can quickly obtain a shell model that fit for robot.At the same time, it can avoid collision between shell model and the robot endoskeleton.