VVG05

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https://diglib.eg.org/handle/10.2312/1030

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Color Reduction by Using a new Self-Growing and Self-Organized Neural Network
(The Eurographics Association, 2005) Atsalakis, A.; Papamarkos, N.; Mike Chantler
A new method for the reduction of the number of colors in a digital image is proposed. The new method is based on the developed of a new neural network classifier that combines the advantages of the Growing Neural Gas (GNG) and the Kohonen Self-Organized Feature Map (SOFM) neural networks. We call the new neural network: Self-Growing and Self- Organized Neural Gas (SGONG). Its main advantage is that it defines the number of the created neurons and their topology in an automatic way. As a consecutive, isolated color classes, which may correspond to significant image details, can be obtained. The SGONG is fed by the color components and additional spatial features. To speed up the entire algorithm and to reduce memory requirements, a fractal scanning sub-sampling technique is used. The method is applicable to any type of color images and it can accommodate any type of color space.
Rigorous Computing in Computer Vision
(The Eurographics Association, 2005) Farenzena, Michela; Fusiello, Andrea; Mike Chantler
In this paper we discuss how Interval Analysis can be used to solve some problems in Computer Vision, namely autocalibration and triangulation. The crucial property of Interval Analysis is its ability to rigorously bound the range of a function over a given domain. This allows to propagate input errors with guaranteed results (used in multi-views triangulation) and to search for solution in non-linear minimisation problems with provably correct branch-and-bound algorithms (used in autocalibration). Experiments with real calibrated images illustrate the interval approach.
A Rigid Transform Basis for Animation Compression and Level of Detail
(The Eurographics Association, 2005) Collins, G.; Hilton, A.; Mike Chantler
We present a scheme for achieving level of detail and compression for animation sequences with known constant connectivity. We suggest compression is useful to automatically create low levels of detail in animations which may be more compressed than the original animation parameters and for high levels of detail where the original animation is expensive to compute. Our scheme is based on spatial segmentation of a base mesh into rigidly transforming segments and then temporal aggregation of these transformations. The result will approximate the given animation within a user specified tolerance which can be adjusted to give the required level of detail. A spatio-temporal smoothing algorithm is used on decoding to give acceptable animations. We show that the rigid transformation basis will span the space of all animations. We also show that the algorithm will converge to the specified tolerance. The algorithm is applied to several examples of synthetic animation and rate distortion curves are given which show that in some cases, the scheme outperforms current compressors.
Depth Enhanced Panoramas
(The Eurographics Association, 2005) Bahmutov, Gleb; Popescu, Voicu; Mudure, Mihai; Sacks, Elisha; Mike Chantler
Depth enhanced panoramas are a practical solution to the difficult problem of inside-looking-out modeling. Depth enhanced panoramas extend color panoramas to support viewpoint translation, while retaining their speed, convenience, and low cost. Depth enhanced panoramas are built incrementally from same-center-of-projection dense-color and sparse-depth frames that are acquired, registered, and merged at the rate of 5 frames per second. The evolving depth enhanced panorama is rendered continually to provide immediate operator feedback. The viewpoint translation range is increased by combining multiple depth enhanced panoramas in real time. Depth enhanced panoramas are combined using either a splat-based, disconnected representation, or, at pixel level, using a GPU fragment program. Depth enhanced panoramas are built in minutes with $3,000 hardware and support photorealistic rendering of complex room-sized environments.
SVD-Matching using SIFT Features
(The Eurographics Association, 2005) Delponte, Elisabetta; Isgrò, Francesco; Odone, Francesca; Verri, Alessandro; Mike Chantler
The paper tackles the problem of feature points matching between pair of images of the same scene. This is a key problem in computer vision. Among the many possible applications of feature matching we are motivated for helping in the initialisation of a 3D registration procedure. The method we discuss here is a version of the SVD matching proposed by Pilu, modified in order to cope with large scale variations. We detail the algorithm and present experimental evidence of the improvement in performance. The main contribution of this work is in showing that this compact and easy algorithm can be used for large-baseline matching.
Visual Recognition of Man-made Materials and Structures in an Office Environment
(The Eurographics Association, 2005) Song, Y. Z.; Town, C. P.; Mike Chantler
This paper demonstrates a new approach towards object recognition founded on the development of Neural Network classifiers and Bayesian Networks. The mapping from segmented image region descriptors to semantically meaningful class membership terms is achieved using Neural Networks. Bayesian Networks are then employed to probabilistically detect objects within an image by means of relating region class labels and their surrounding environments. Furthermore, it makes use of an intermediate level of image representation and demonstrates how object recognition can be achieved in this way.
Use of Computer Vision/ Computer Graphics Collaboration for 3D Rotoscopy
(The Eurographics Association, 2005) Gagalowicz, André; Mike Chantler
This talk introduces 3D rotoscopy and its role in post-production applications, and the computer vision/computer graphics strategies used. The case of rigid objects is presented first, for which well-established approaches can be used. The case of articulated objects is considered next, with special attention to the case of a full human body tracking (ignoring significant shape deformations introduced by baggy clothes). Results related to the tracking of professional golfers and face tracking, a challenging case of deformable objects, will be presented. The talk will be concluded by a presentation of further, possible applications of research done at the MIRAGES laboratory at INRIA Rocquencourt.
A New Framework for Trademark Retrieval Based on Size Functions
(The Eurographics Association, 2005) Cerri, A.; Ferri, M.; Giorgi, D.; Mike Chantler
We propose a new, effective system for Content Based trademark retrieval, which involves Size Functions. Three different classes of shape descriptors are combined, for a total amount of 25 measuring functions. The evaluation has been performed on a database of 1182 trademark images, provided by the UK Patent Office.
Bitvectors for Robust Hierarchical Template Matching
(The Eurographics Association, 2005) Tweed, David; Mike Chantler
Many target detection problems involve objects where the primary variability in appearance is due to changes amongst characteristic configurations (as opposed to the systematic variability of object rotation or illumination changes). It is then important to utilise as much of the correlation between features as possible. Detecting pedestrians is such a problem and was tackled by Gavrila [Gav98] using a large set of exemplar templates combined with hierarchical matching via Distance Transforms. We describe a variant using a robust distance function and explicit allowance for occlusions. Our innovation is using bitwise logical operators to test against multiple exemplars in parallel.
Sensitivity Analysis in Image Synthesis
(The Eurographics Association, 2005) Trujillo, M.; Izquierdo, E.; Mike Chantler
Intermediate virtual images are used in the evaluation of disparity estimations. The analysis is based on the effect of disparity inaccuracies in the relative quality of virtual images. The peak-signal-to-noise ratio and the percentage of visual errors are used to assess the quality of virtual images generated with distorted disparity fields. Computer simulation results show that the peak-signal-to-noise ratio is more affected by a small magnitude of perturbations two or three pixels than by a high frequency of perturbations 15% or 20%. However, the percentage of visual errors is more affected by the frequency of perturbations. By using distorted disparity fields, the deterioration in the quality of virtual images is imperceptible to the human eye.
Regularised Anisotropic Nonlinear Diffusion for Rendering Refraction in Volume Graphics
(The Eurographics Association, 2005) Rodgman, David; Chen, Min; Mike Chantler
Rendering refraction in volume graphics requires smoothly distributed normals to synthesise good quality visual representations. Such refractive visualisation is more susceptible to noise in the data than visualisations that do not involve refraction. In this paper, we addresses the need for improving the continuity of voxel gradients in discretely sampled volume datasets using nonlinear diffusion methods, which was originally developed for image denoising. We consider the necessity for minimising unnecessary geometrical distortion, detail the functional specification of a volumetric filter for regularised anisotropic nonlinear diffusion (R-ANLD), discuss the further improvements of the filter, and compare the efficacy of the filter with an anisotropic nonlinear diffusion (ANLD) filter as well as a Gaussian filter and a linear diffusion filter. Our results indicate that it is possible to make significant improvements in image quality in refractive rendering without excessive distortion.
Correspondenceless Stereo for 3-D Iris Location
(The Eurographics Association, 2005) Anderson, Tom; Trucco, Emanuele; Razeto, Marco; Mike Chantler
We present a correspondenceless stereo system locating the circular contour of an iris (limbus) in space, and therefore its 3-D plane. We avoid correspondence search completely by intersecting a bundle of conjugate epipolar lines with the elliptical images of the limbus in the stereo pair of images, which gives correspondences directly. The ellipses are located by active ellipse fitting. An efficient simulated annealing implementation achieves reliable iris location with uncontrolled illumination and eye or head movements. Tests with ground-truthed 3-D setups as well as real eye images indicate very good accuracy.
Texture Mapping Volume Objects
(The Eurographics Association, 2005) Shen, P.; Willis, P.; Mike Chantler
We present a combination of image-based texture mapping and projective space (pseudo-solid) texture. This imagebased texture mapping is useful for objects defined from volume datasets. The paper makes three main contributions. First, it introduces the combination of the image-based two-part texture mapping and projective space texture mapping for volume objects. Second, it presents a multi-resolution technique to overcome problems with projecting at glancing angles and to eliminate artifacts due to the resolution limitations. Third, it presents the pixel-level data-dependent interpolation technique in projective image warping. The proposed approach leads to superior quality of texture and thus provides an optional solution for texturing volume objects.The results show the effectiveness and quality of rendered images.
Merging Graphics and Vision for 3D Face Recognition
(The Eurographics Association, 2005) Bai, Li; Song, Yi; Mike Chantler
This paper presents a new approach to automatic 3D face modelling from unstructured point cloud data. An efficient B-Spline surface-fitting algorithm is used to obtain an initial parametric surface for each face point cloud data set. Knot vectors for each individual face surface are then standardised to produce a set of uniform knot vectors so that all the surfaces can be seen as fitted with the same set of knot vectors. Mapping from object space to shape space can then be established so that each 3D face can be described by a small number of shape descriptors. The use of shape descriptors allows automatic registration between face models. More importantly, it allows dynamic facial variation to be modelled and analysed via 3D warping, resulting in a powerful approach to quantifying the differences among individuals required for face recognition. 3D warping is often used in simulations in computer graphics. This paper explains, for the first time, how 3D warping can be exploited for face recognition based on multi-resolution analysis of warping fields. The methodology allows the quantitative study of variation in characteristics previously only described from a qualitative perspective.
Talking Faces - Technologies and Applications
(The Eurographics Association, 2005) Ostermann, Jörn; Weissenfeld, Axel; Liu, Kang; Mike Chantler
Facial animation has been combined with text-to-speech synthesis to create innovative multimodal interfaces. In this lecture, we present the technology and architecture in order to use this multimodal interface in an web-based environment to support education, entertainment and e-commerce applications. Modern text to speech synthesizers using concatenative speech synthesis are able to generate high quality speech. Face animation uses the phoneme and timing information provided by such a speech synthesizer in order to animate the mouth. There are 2 basic technologies that are used to render talking faces: 3D face models as described in MPEG-4 may be used to provide the impression of a talking cartoon or human-like character. Sample-based face models generated from recorded video enable the synthesis of a talking head that cannot be distinguished from a real person. Depending on the chosen face animation technology and latency requirements, different architectures for delivering the talking head over the Internet are required for interactive applications. Keywords: Face animation, visual speech
Table of Contents and Preface
(The Eurographics Association, 2005) Mike Chantler
Multi-View Image Coding with Wavelet Lifting Scheme
(The Eurographics Association, 2005) Anantrasirichai, N.; Canagarajah, C. Nishan; Bull, David R.; Mike Chantler
In this paper, we present a novel multi-view image codec based on a wavelet lifting scheme. The proposed algorithm applies the disparity estimation and compensation with the lifting scheme. It is very efficient in terms of compressions performance, memory requirements and fast computation. To get the highest multiview image coding efficiencies, two hybrid predictions are proposed; one for effective compression performance and one for compromising when more exact disparity values are required. Moreover, an adaptive weighing in update step and overlapped block disparity compensation are included to yield significant improvements in rate distortion performance. Experimental results show image quality gains of up to 2 dB and 1 dB against using well established methods such as the block-matching Haar and 5/3 wavelet lifting respectively.
Advances in Shadow Removing for Motion Detection Algorithms
(The Eurographics Association, 2005) Spagnolo, P.; D'Orazio, T.; Leo, M.; Distante, A.; Mike Chantler
Detecting moving objects is very important in many application contexts such as people detection and recognition, visual surveillance, automatic generation of video effects, and so on. Motion detection algorithms are very sensible to light conditions; in particular they suffer the presence of shadows and sudden changes due to light switches. Here we propose an additional module that can be applied to a generic gray-level motion detection algorithm. The only requirement is the presence of a reference image (background model). The main idea of the proposed approach is that variations in light conditions alter the intensity values of pixels in the image, but the basic structures in the scene remain unchanged. The algorithm we propose is based on the correlation between regions selected from the reference image and the current one. The experiments have been performed on image sequences acquired both in indoor and outdoor environments with natural and artificial lights.
3D Image Analysis and Synthesis at MPI Informatik
(The Eurographics Association, 2005) Theobalt, Christian; Magnor, Marcus A.; Seidel, Hans-Peter; Mike Chantler
In the talk, we give a brief overview of the research done in the Computer Graphics Group and the Graphics- Optics-Vision Group of the Max-Planck-Institut für Informatik in the area of 3D Image Analysis and Synthesis. In this context, we address the whole pipeline ranging from the acquisition of computational scene models, over the algorithmic processing of these scene descriptions, to their photo-realistic rendition in the computer. This paper illustrates the questions that we are trying to answer by means of one of our research projects, video-based rendering. We have developed a model-based system to acquire, reconstruct and render free-viewpoint videos of human actors that nicely illustrates the concept of 3D Image Analysis and Synthesis.
Modeling Falling and Accumulating Snow
(The Eurographics Association, 2005) Moeslund, T. B.; Madsen, C. B.; Aagaard, M.; Lerche, D.; Mike Chantler
The use of computer graphics to produce special effects is currently being applied with great results in especially the entertainment and game industry. One area where computer graphics is not quite ready to replace all real effects is natural phenomena where a lack of general models exists. In this work we present a general model for falling and accumulating snow. The appearance and movement of falling snow are modeled in 3D based on the physics governing the real processes. The same goes for the accumulated snow where especially a correctly modeled wind field is important for producing realistically looking results. Intuitive weather parameters are used to control both models. The results show that both the appearance and movement of the snow, as well as the accumulated snow are very similar to real snow.

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