Deformable Objects Research Papers - Academia.edu (original) (raw)

We are presenting techniques for simulating the motion and the deformation of cloth, fabrics or, more generally, deformable surfaces. Our main goal is to be able to simulate any kind of surface without imposing restrictions on shape or geometrical environment. In particular, we are considering difficult situations with respect to deformations and collisions, like wrinkled fabric falling on the ground. Thus, we have enhanced existing algorithms in order to cope with any possible situation. A mechanical model has been implemented to deal with any irregular triangular meshes, handle high deformations despite rough discretisation, and cope with complex interacting collisions. Thus, it should deal efficiently with situations where nonlinearities and discontinuities are really non marginal. Collision detection has also been improved to efficiently detect self-collisions, and also to correctly consider collision orientations despite the lack of surface orientation information from preset geometrical contexts, using consistency checking and correction. We illustrate these features through simulation examples.

- by
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- Animation, Deformable Objects, Collision detection, Consistency Checking

This paper presents a hybrid geometrical-physical, plastic deformation technique applicable for solids, in the context of a car simulation game. This technique doesn't aim to be mechanically correct but to produce visual appealing and... more

- by rui pires
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- Game Development, Dynamics, Deformable Objects, Collision detection

Computer haptics, an emerging field of research that is analogous to computer graphics, is concerned with the generation and rendering of haptic virtual objects. In this paper, we propose an efficient haptic rendering method for displaying the feel of 3-D polyhedral objects in virtual environments (VEs). Using this method and a haptic interface device, the users can manually explore and feel the shape and surface details of virtual objects. The main component of our rendering method is the ''neighborhood watch'' algorithm that takes advantage of precomputed connectivity information for detecting collisions between the end effector of a force-reflecting robot and polyhedral objects in VEs. We use a hierarchical database, multithreading techniques, and efficient search procedures to reduce the computational time such that the haptic servo rate after the first contact is essentially independent of the number of polygons that represent the object. We also propose efficient methods for displaying surface properties of objects such as haptic texture and friction. Our haptic-texturing techniques and friction model can add surface details onto convex or concave 3-D polygonal surfaces. These haptic-rendering techniques can be extended to display dynamics of rigid and deformable objects.

- by Cagatay Basdogan
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- Point-Based Rendering, Presence, Virtual Environment, Deformable Objects

. A spherical hash approach is used to handle collisions between complex deformable models in constant time to the number of vertices. The first image shows a tetrahedral mesh encapsulated into its spherical bounding. The other images present frames of real-time animations involving one, two, three and four colliding deformable objects. Since our case study is on surgical simulation, we are using a reconstructed and decimated real liver to exemplify.

- by Anderson Maciel
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- Surgery, Parallel Programming, Real Time Computing, Computer Animation

A structured computational framework to efficiently detect collision between deformable freeform shapes in a VR environment is proposed in this paper. The deformable shape is represented as a B-spline surface and no assumption is made with regard to the degree of the surface, extent of deformation or virtual material properties. The proposed technique calculates and stores transformation matrices and their

- by George Knopf
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- Mechanical Engineering, Computer Aided Design, Haptics, Level Of Detail (LOD)

This paper discusses the use of physics-based models for animating clothes on synthetic actors in motion. In our approach, cloth pieces are first designed with polygonal panels in two dimensions, and are then seamed and attached to the actor's body in three dimensions. After the clothes are created, physical properties are simulated and then clothes are animated according to the actor's motion in a physical environment. We describe the physical models we use and then address several problems we encountered. We examine how to constrain the elements of deformable objects which are either seamed together or attached to rigid moving objects. We also describe a new approach to the problem of handling collisions among the cloth elements themselves, or between a cloth element and a rigid object like the human body. Finally, we discuss how to reduce the number of parameters for improving the interface between the animator and the physics-based model.

- by Nadia Magnenat-thalmann
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- Computer Graphics, Human Body, Deformable Objects, Physical Environment

Phase unwrapping is a task common to many applications like interferometry imaging, medical magnetic resonance imaging, solidstate physics, etc. Fourier transform profilometry (FTP) values the height distribution of object, elaborating the interference between a plane reference grating and a deformed object grating. Since the height information is extracted from the phase of a complex function, the phase unwrapping is a critical step of the process. Several unwrapping algorithms are proposed in literature, but applied to measurement technologies different from FTP. The purpose of this paper is to define the performances of eight different unwrapping algorithms applied to FTP optical scan method and to define the best one. The algorithms chosen are: Goldstein's algorithm, quality guided path following method, Mask cut method, Flynn's method, multi-grid method, weighted multi-grid method, preconditioned conjugate gradient method and minimum L p -norm method. The methods were tested on real images acquired by a FTP scanner developed and calibrated for these experiments. The objects used vary from simple geometries, like planes and cylinders, to complex shapes of common use objects. Algorithms were qualified considering the phase unwrapping errors, execution time and accuracy of the shape of objects obtained from the scan method in comparison with real ones. The results show that quality guided algorithm best fits in FTP application. r

- by Guido Busca
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- Deformable Objects, Phase Unwrapping, Optical physics, Fourier transform

Motion detection is the first essential process in the extraction of information regarding moving objects and makes use of stabilization in functional areas such as tracking, classification, recognition, and so on. In this paper, high-quality moving object detection is determined by using nonparametric modeling. The background is modeled by using the combination of chromaticity and gradients; it reduces the influence of shadows and reflected light. The foreground model combines this information and spatial information. Particle filter is introduced update the spatial information. The detection results produced by the particle filter is analysed through visual inspection and for accuracy, along with comparisons to the results produced by other state-of-the-art methods.

Photometric Stereo is a powerful image based 3d reconstruction technique that has recently been used to obtain very high quality reconstructions. However, in its classic form, Photometric Stereo suffers from two main limitations: Firstly, one needs to obtain images of the 3d scene under multiple different illuminations. As a result the 3d scene needs to remain static during illumination changes, which prohibits the reconstruction of deforming objects. Secondly, the images obtained must be from a single viewpoint. This leads to depth-map based 2.5 reconstructions, instead of full 3d surfaces. The aim of this chapter is to show how these limitations can be alleviated, leading to the derivation of two practical 3d acquisition systems: The first one, based on the powerful Coloured Light Photometric Stereo method can be used to reconstruct moving objects such as cloth or human faces. The second, permits the complete 3d reconstruction of challenging objects such as porcelain vases. In addition to algorithmic details, the chapter pays attention to practical issues such as setup calibration, detection and correction of self and cast shadows. We provide several evaluation experiments as well as reconstruction results.

- by Carlos Hernández
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- Deformable Objects, 3-D Reconstruction, Photometric Stereo, Depth Map
- by Emanuele Zappa
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- Deformable Objects, Phase Unwrapping, Optical physics, Fourier transform

This paper presents an enhanced haptic-enabled master-slave teleoperation system which can be used to provide force feedback to surgeons in minimally invasive surgery (MIS). One of the research goals was to develop a combined-control architecture framework that included both direct force reflection (DFR) and position-error-based (PEB) control strategies. To achieve this goal, it was essential to measure accurately the direct contact forces between deformable bodies and a robotic tool tip. To measure the forces at a surgical tool tip and enhance the performance of the teleoperation system, an optical force sensor was designed, prototyped, and added to a robot manipulator. The enhanced teleoperation architecture was formulated by developing mathematical models for the optical force sensor, the extended slave robot manipulator, and the combined-control strategy. Human factor studies were also conducted to (a) examine experimentally the performance of the enhanced teleoperation system w...

- by Mehrdad Zadeh
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- Robotics, Algorithms, Human Factors, Haptics

This paper addresses issues in object tracking where videos contain complex scenarios. We propose a novel tracking scheme that jointly employs particle filters and multi-mode anisotropic mean shift. The tracker estimates the dynamic shape and appearance of objects, and also performs online learning of reference object. Several partition prototypes and fully tunable parameters are applied to the rectangular object bounding box for improving the estimates of shape and multiple appearance modes in the object. The main contributions of the proposed scheme include: 1) use a novel approach for online learning of reference object distributions; 2) use a five parameter set (2-D central location, width, height, and orientation) of rectangular bounding box as tunable variables in the joint tracking scheme; 3) derive the multi-mode anisotropic mean shift related to a partitioned rectangular bounding box and several partition prototypes; and 4) relate the bounding box parameter computation with the multi-mode mean shift estimates by combining eigendecomposition, geometry of subareas, and weighted average. This has led to more accurate and efficient tracking where only small number of particles (<20) is required. Experiments have been conducted for a range of videos captured by a dynamic or stationary camera, where the target object may experience long-term partial occlusions, intersections with other objects with similar color distributions, deformable object accompanied with shape, pose or abrupt motion speed changes, and cluttered background. Comparisons with existing methods and performance evaluations are also performed. Test results have shown marked improvement of the proposed method in terms of robustness to occlusions, tracking drifts and tightness and accuracy of tracked bounding box. Limitations of the method are also mentioned.

- by Irene Y.H. Gu
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- Online Learning, Target Tracking, Performance Evaluation, Object Tracking

The particle filtering technique with multiple cues such as colour, texture and edges as observation features is a powerful technique for tracking deformable objects in image sequences with complex backgrounds. In this paper, our recent work [1] on single object tracking using particle filters is extended to multiple objects. In the proposed scheme, track initialisation is embedded in the particle filter without relying on an external object detection scheme. The proposed scheme avoids the use of hybrid state estimation for the estimation of number of active objects and its associated state vectors as proposed in . The number of active objects and track management are handled by means of probabilities of the number of active objects in a given frame. These probabilities are shown to be easily estimated by the Monte Carlo data association algorithm used in our algorithm.

- by Lyudmila Mihaylova and +1
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- Monte Carlo, State Estimation, Object Tracking, Deformable Objects
- by Jeremy L Wyatt and +1
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- Artificial Intelligence, Machine Learning, Play, Cognitive Robotics

Real-time evaluation of distributed contact forces between rigid or deformable 3D objects is a key ingredient of 6-DoF force-feedback rendering. Unfortunately, at very high temporal rates, there is often insufficient time to resolve contact between geometrically complex objects. We propose a spatially and temporally adaptive approach to approximate distributed contact forces under hard real-time constraints. Our method is CPU-based and supports contact between rigid or reduced deformable models with complex geometry. We propose a contact model that uses a point-based representation for one object and a signed-distance field for the other. This model is related to the Voxmap-PointShell (VPS) method, but gives continuous contact forces and torques, enabling stable rendering of stiff penalty-based distributed contacts. We demonstrate that stable haptic interactions can be achieved by point-sampling offset surfaces to input "polygon soup" geometry using particle repulsion. We introduce a multiresolution nested pointshell construction that permits level-of-detail contact forces and enables graceful degradation of contact in close-proximity scenarios. Parametrically deformed distance fields are proposed for contact between reduced deformable objects. We present several examples of 6-DoF haptic rendering of geometrically complex rigid and deformable objects in distributed contact at real-time kilohertz rates.

Interactive environments for dynamically deforming objects play an important role in surgery simulation and entertainment technology. These environments require fast deformable models and very efficient collision handling techniques. While collision detection for rigid bodies is well-investigated, collision detection for deformable objects introduces additional challenging problems. This paper focuses on these aspects and summarizes recent research in the area of deformable collision detection. Various approaches based on bounding volume hierarchies, distance fields, and spatial partitioning are discussed. Further, image-space techniques and stochastic methods are considered. Applications in cloth modeling and surgical simulation are presented.

Background-While an update rate of 30 Hz is considered adequate for real time graphics, a much higher update rate of about 1 kHz is necessary for haptics. Physics-based modeling of deformable objects, especially when large nonlinear deformations and complex nonlinear material properties are involved, at these very high rates is one of the most challenging tasks in the development of real time simulation systems. While some specialized solutions exist, there is no general solution for arbitrary nonlinearities.

- by Suvranu De
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- Real Time Computing, Multimodal Interaction, Neural Network, Laparoscopic Surgery
- by Andrei Zaharescu
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- Information Systems, Algorithms, Computer Vision, Shape Modeling

We present an approach to real-time animation of deformable objects. Optimization of algorithms using compactly supported radial basis functions (CSRBF) allows us to generate deformations performed fast enough for such real-time applications as computer games. The algorithm described in detail in this paper uses space mapping technique. Smooth local deformations of animation objects can be defined by only a moderate

- by Mikhail Senin
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- Radial Basis Function, Deformable Objects, Real Time, Real Time Application

In this paper, we present a new SH operation, called spherical harmonics scaling, to shrink or expand a spherical function in the frequency domain. We show that this problem can be elegantly formulated as a linear transformation of SH projections, which is efficient to compute and easy to implement on a GPU. Spherical harmonics scaling is particularly useful for extrapolating visibility and radiance functions at a sample point to points closer to or farther from an occluder or light source. With SH scaling, we present applications to low-frequency shadowing for general deformable object, and to efficient approximation of spherical irradiance functions within a mid-range illumination environment.

- by Shi-min Hu
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- Cognitive Science, Signal Processing, Low Frequency, Deformable Objects

The equations of motion for a system of multiple mobile manipulators that handle a deformable object during an agricultural task are developed. The model is based on Kane's approach. The imposed kinematic constraints are included and incorporated into the dynamics. Sufficient conditions for avoiding tipping over of the mechanisms are also provided. The deformable nature of the object can easily

Simulations of flow and heat transfer around deforming objects require the accurate resolution of the moving interface. An approach that combines the Hybrid Immersed Boundary Method (HIBM) for handling complex moving boundaries and the Material Point Method (MPM) for resolving structural stresses and the movement of the deformable body is presented here. In the HIBM, a fixed Eulerian, curvilinear grid is generally defined, and the variable values at grid points adjacent to a curvilinear boundary are interpolated to satisfy the boundary conditions. The MPM is used to solve equations of the solid structure (stresses and deflection) and communicates with the flow equations through appropriate interface-boundary conditions. As a validation of the new approach for heat transfer problems, flow and heat transfer past a rigid and deforming isothermal sphere is simulated. Predictions agree well with published results of Nusselt number for flow past a rigid sphere.

- by Anvar Gilmanov
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- Engineering, Heat Transfer, Fluid structure interaction, Heat and Mass Transfer

Abstract In this paper an algorithm which is able to count the number of fingers from a hand posture is presented. The method is based on hand contour and skin colour information. The middle axes of the fingers are detected. The method is... more

- by Vasile Gui and +1
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- Human Computer Interaction, Computer Vision, Sign Language, Gesture Recognition

Mass-Spring systems are used widely to implement animation of deformable objects. We have developed a simple mass-spring system to animate a character ba sed on physics. The reason we adopt a mass-spring system i s simply we wanted more realism than Free Form Deformation (FFD) techniques can offer, as modeling physical processes. Also, this technique is preferr ed over Finite Element Methods (FEM) because these methods are computationally expensive and not always is possibl e to develop real time applications using them. Instead, Mass- Spring systems offer physically based behavior toge ther with interactive and, sometimes, real time simulati ons. In addition, our implementation of the physic model ca n be used for a more general application, not only anima tion.

The dynamic equations of motion for a system of multiple mobile manipulators carrying a common deformable object are developed. The derived centralized model is based on Kane's approach to dynamics. The imposed kinematic nonholonomic constraints are included and incorporated into the dynamics. It is pointed out, however, that these kinematic constraints are only necessary, and they only become su cient to impose nonholonomic motion when accompanied by the dynamic counterparts. Su cient conditions for avoiding tipping over by the mechanisms are also provided. The whole set of constraint equations is analyzed and useful properties for the set of admissible solutions for the ground reaction forces are obtained. The deformable object under manipulation is modeled and the simplest approximating grid structure is indicated.

We present a photometric stereo method for non-rigid objects of unknown and spatially varying materials. The prior art uses timemultiplexed illumination but assumes constant surface normals across several frames, fundamentally limiting the accuracy of the estimated normals. We explicitly account for time-varying surface orientations, and show that for unknown Lambertian materials, five images are sufficient to recover surface orientation in one frame. Our optimized system implementation exploits the physical properties of typical cameras and LEDs to reduce the required number of images to just three, and also facilitates frame-to-frame image alignment using standard optical flow methods, despite varying illumination. We demonstrate the system's performance by computing surface orientations for several different moving, deforming objects.

- by Moshe Ben-ezra
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- Optical Flow, Deformable Objects, ECCV, Photometric Stereo

- by Daniel Thalmann
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- Human Body, Deformable Objects, Physical Environment, Moving Object Recognition
- by Jackie Chappell
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- Artificial Intelligence, Machine Learning, Play, Cognitive Robotics

In this paper we describe a system for physical anima- tion of rigid and deformable objects. These are represented as groups of particles linked by linear constraints, while a Verlet integrator is used for motion computation. Unlike traditional approaches, we accomplish physical simulatio n without explicitly computing orientation matrices, torqu es or inertia tensors. The main contribution of our work

Figure 1: Decomposing Vector Fields: the tangential component of a wind field interacting with an ear (left, LIC visualization [5]) reveals its curl free component (middle) and divergence-free component (right) after decomposition. In this paper, simple computational tools are introduced to produce such a decomposition, for discrete 2D and 3D vector fields defined on irregular grids, even on curved manifolds.

- by Yiying Tong
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- Information Systems, Visualization, Animation, Data Visualization

HIRO (Haptic Interface RObot) is a new device that enables users to interact and feel the virtual object safely. Hand interaction with virtual object requires a more elaborated model than the Haptic Interaction Point (HIP) due to the complex shape of the virtual hand. This paper describes a general approach called the Haptic Interaction Poly technique for haptic rendering of 3D object for hand interaction that takes in consideration the real shape, as well as the orientation of the hand and accounts for the shape of the interacting objects. Moreover, a physically-based modeling is achieved by using a Finite Element Method (FEM) to simulate deformable objects and provides correct reaction forces and deformations. A VR medical application system for breast palpation using HIRO was developed in which the proposed haptic interaction method was implemented and tested. The experiments showed that the system was able to provide the users with a realistic haptic sensation in addition to sufficient graphical update rate considering deformable object.

This paper describes a computer vision approach to automated rapid-throughput taxonomic identification of stonefly larvae. The long-term objective of this research is to develop a cost-effective method for environmental monitoring based on automated identification of indicator species. Recognition of stonefly larvae is challenging because they are highly articulated, they exhibit a high degree of intraspecies variation in size and color, and some species are difficult to distinguish visually, despite prominent dorsal patterning. The stoneflies are imaged via an apparatus that manipulates the specimens into the field of view of a microscope so that images are obtained under highly repeatable conditions. The images are then classified through a process that involves (a) identification of regions of interest, (b) representation of those regions as SIFT vectors (Lowe, in Int J Comput Vis 60(2):91–110, 2004) (c) classification of the SIFT vectors into learned “features” to form a histogram of detected features, and (d) classification of the feature histogram via state-of-the-art ensemble classification algorithms. The steps (a) to (c) compose the concatenated feature histogram (CFH) method. We apply three region detectors for part (a) above, including a newly developed principal curvature-based region (PCBR) detector. This detector finds stable regions of high curvature via a watershed segmentation algorithm. We compute a separate dictionary of learned features for each region detector, and then concatenate the histograms prior to the final classification step. We evaluate this classification methodology on a task of discriminating among four stonefly taxa, two of which, Calineuria and Doroneuria, are difficult even for experts to discriminate. The results show that the combination of all three detectors gives four-class accuracy of 82% and three-class accuracy (pooling Calineuria and Doro-neuria) of 95%. Each region detector makes a valuable contribution. In particular, our new PCBR detector is able to discriminate Calineuria and Doroneuria much better than the other detectors.

- by Natalia Larios
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- Zoology, Cognitive Science, Computer Vision, Machine Vision

Computer games and real-time applications frequently adopt mesh skinning as a deformation technique for virtual characters and articulated objects. Rendering skinned models with global shading effects, such as interreflection and subsurface scattering, using precomputed radiance transfer enables high-quality real-time display of dynamically deformed objects. In this approach, we need to precompute radiance transfer for many sampled poses. Resulting datasets reach hundreds of gigabytes, and are orders of magnitude larger than those for a static object. This paper presents simple but effective large-scale data management techniques so that runtime data communication, decompression and interpolation can be performed efficiently and accurately. Specifically, we have developed a mesh clustering technique based on spectral graph partitioning to facilitate interpolation from nearest neighbors and an incremental clustering method for transfer matrix compression. By exploiting additional data redundancies among different sampled poses, we can achieve higher compression ratios with the same fidelity. Our incremental clustering can make the runtime cost of per-frame data decompression and interpolation satisfy a prescribed upper bound. As a result, we can achieve real-time performance using the massive precomputed data and an efficient runtime algorithm.

- by Armadillo Games
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- Data Management, Real-time rendering, Nearest Neighbor, Deformable Objects

The paper is dedicated to haptic rendering of complex physics-based environment in the context of surgical simulation. A new unified formalism for modeling the mechanical interactions between medical devices and anatomical structures and for computing accurately the haptic force feedback is presented. The approach deals with the mechanical interactions using appropriate force and/or motion transmission models named compliant mechanisms. These mechanisms are formulated as a constraint-based problem that is solved in two separate threads running at different frequencies. The first thread processes the whole simulation including the softtissue deformations, whereas the second one only deals with computer haptics. This method builds a bridge between the so-called virtual mechanisms (that were proposed for haptic rendering of rigid bodies) and intermediate representations (used for rendering of complex simulations). With this approach, it is possible to describe the specific behavior of various medical devices while relying on a unified method for solving the mechanical interactions between deformable objects and haptic rendering. The technique is demonstrated in interactive simulation of flexible needle insertion through soft anatomical structures with force feedback.

- by Igor Peterlik and +1
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- Surgery, Haptic Interface Design, Computer Model, Compliant Mechanisms

Active appearance model (AAM) is a powerful generative method for modeling deformable objects. The model decouples the shape and the texture variations of objects, which is followed by an efficient gradient-based model fitting method. Due to the flexible and simple framework, AAM has been widely applied in the fields of computer vision. However, difficulties are met when it is applied to various practical issues, which lead to a lot of prominent improvements to the model. Nevertheless, these difficulties and improvements have not been studied systematically. This motivates us to review the recent advances of AAM. This paper focuses on the improvements in the literature in turns of the problems suffered by AAM in practical applications. Therefore, these algorithms are summarized from three aspects, i.e., efficiency, discrimination, and robustness. Additionally, some applications and implementations of AAM are also enumerated. The main purpose of this paper is to serve as a guide for further research.

- by Xinbo Gao
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- Engineering, Computer Vision, Power Generation, Deformable Objects

- by Carlos Hernández
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- Deformable Objects, 3-D Reconstruction, Photometric Stereo, Depth Map

The present paper describes the integration of a multi-finger haptic device with deformable objects in an interactive environment. Repulsive forces are synthesized and rendered independently for each finger of a user wearing a Cybergrasp force-feedback glove. Deformation and contact models are based on mass-spring systems, and the issue of the user independence is dealt with through a geometric calibration phase. Motivated by the knowledge that human hand plays a very important role in the somatosensory system, we focused on the potential of the Cybergrasp device to improve perception in Virtual Reality worlds. We especially explored whether it is possible to distinguish objects with different elasticities. Results of performance and perception tests are encouraging despite current technical and computational limitations.

We present an algorithm for tracking video object which is based on an hybrid strategy. This strategy uses both object and region information to solve the correspondence problem. Low level descriptors are exploited to track object's regions and to cope with track management issues. Appearance and disappearance of objects, splitting and partial occlusions are resolved through interactions between regions and objects. Experimental results demonstrate that this approach has the ability to deal with multiple deformable objects, whose shape varies over time. Furthermore, it is very simple, because the tracking is based on the descriptors, which represent a very compact piece of information about regions, and they are easy to define and track automatically. Finally, this procedure implicitly provides one with a description of the objects and their track, thus enabling indexing and manipulation of the video content.

- by Olivier Cavallaro
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- Data Mining, Object Tracking, Video Object, Deformable Objects

Abstract. Artificial Intelligence (AI) and Animal Cognition (AC) share a common goal: to study learning and causal understanding. However, the perspectives are completely different: while AC studies intelligent systems present in nature, AI tries to to build them almost from scratch. It is proposed here that both visions are complementary and should interact more to better achieve their ends. Nonetheless, before efficient collaboration can take place, a greater mutual understanding of each field is required, beginning with clarifications of their ...

- by Jeremy L Wyatt and +1
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- Artificial Intelligence, Animal Behavior, Cognitive Robotics, Animal Cognition

Besides finite element method, mass-spring system is widely used in Computer Graphics. It is indubitably the simplest and most intuitive deformable model that takes into account elastic considerations. This discrete model allows to perform with ease interactive deformations as well as to handle complex interactions. Thus, it is perfectly adapted to generate visually plausible animations. However, a drawback of this simple formulation is the relative difficulty to control efficiently realistic physically-based behaviors. Indeed, none of the existing models has succeeded in dealing with this satisfyingly. Moreover, we demonstrate that the mostly cited technique in the literature, proposed by Van Gelder, is far to be exact in most real cases, and consequently, this model can not be used in simulation. So, we propose a new general 3D formulation that reconstructs the geometrical model as an assembly of elementary hexahedral "bricks". Each brick (or element) is then transformed into a mass-spring system. Edges are replaced by springs that connect masses representing the vertices. The key point of our approach is the determination of the stiffness springs to reproduce the correct mechanical properties (Young's modulus and Poisson's ratio) of the reconstructed object. We validate our methodology by performing some numerical experiments. Finally, we evaluate the accuracy of our approach, by comparing our results with the deformation obtained by finite element method.

- by Fabrice Jaillet
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- Finite element method, Geometric model, Deformable Objects, Computer Graphic

Unwrap mosaic Edited mosaic Output video : Editing a video of a talking head. The input images are automatically converted to an "unwrap mosaic" without an intervening 3D reconstruction. Painting the mosaic and re-rendering the video allows us to add virtual make-up (eyebrows, moustache, and rouge on the cheeks) to the actor, as if to a texture map on a deformable 3D surface.

- by Alex Rav-acha
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- Information Systems, Motion estimation, Deformable Objects, Video Editing

This paper presents a feature point tracking algorithm using optical flow under the non-prior training active feature model (NPT-AFM) framework. The proposed algorithm mainly focuses on analysis of deformable objects, and provides real-time, robust tracking. The proposed object tracking procedure can be divided into two steps: (i) optical flow-based tracking of feature points and (ii) NPT-AFM for robust tracking. In order to handle occlusion problems in object tracking, feature points inside an object are estimated instead of its shape boundary of the conventional active contour model (ACM) or active shape model (ASM), and are updated as an element of the training set for the AFM. The proposed NPT-AFM framework enables the tracking of occluded objects in complicated background. Experimental results show that the proposed NPT-AFM-based algorithm can track deformable objects in real-time.

- by Joonki Paik
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- Multimedia, Optical Flow, Object Tracking, Active Contour Model

Color is a powerful feature for tracking deformable objects in image sequences with complex backgrounds. The color particle filter has proven to be an efficient, simple and robust tracking algorithm. In this paper, we present a hybrid valued sequential state estimation algorithm, and its particle filter-based implementation, that extends the standard color particle filter in two ways. Firstly, target detection and deletion are embedded in the particle filter without relying on an external track initialization and cancellation algorithm. Secondly, the algorithm is able to track multiple objects sharing the same color description while keeping the attractive properties of the original color particle filter. The performance of the proposed filter are evaluated qualitatively on various real-world video sequences with appearing and disappearing targets.

- by Branko Ristic
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- Computer Vision, State Estimation, Particle filters, Visual tracking

In this paper we present a new framework for an accelerated 3D reconstruction of deformable objects within a multi-view setup. It is based on a new memory management and an enhanced algorithm pipeline of the well known Image-Based Visual... more

- by Holger Graf and +1
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- Memory Management, Deformable Objects, 3-D Reconstruction, Digital Human Modeling

In this paper we present a GPU-accelerated implementation of the well-known freeform deformation algorithm to allow for deformable objects within fully interactive virtual environments. We furthermore outline how our real-time deformation approach can be integrated into the X3D standard for more accessibility of the proposed methods. The presented technique can be used to deform complex detailed geometries without pre-processing the mesh by simply generating a lattice around the model. The local deformation is then computed for this lattice instead of the complex geometry, which efficiently can be carried out on the GPU using CUDA.

- by Holger Graf
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- Deformable Objects, Real Time, Mesh Deformation, Real Time Simulation
- by Djamal Merad
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- Computer Vision, Image Processing, Signal Processing, Algorithm