Besides being one of the well-known audio/video coding techniques, MPEG-4 provides additional coding tools dedicated to virtual character animation. The motivation of considering virtual character definition and animation issues within MPEG-4 is first presented. Then, it is shown how MPEG-4, Amendment 1 offers an appropriate framework for virtual human stream is presented and discussed in terms of a generic representation and additional functionalities. The biomechanical properties, modeled by means of the character skeleton that defines the bone influence on the skin region, as well as the local spatial deformations simulating muscles, are supported by specific nodes. Animating the virtual character consists in instantiating bone transformations and muscle control curves. Interpolation techniques, inverse kinematics, discrete cosine transform and arithmetic encoding techniques make it possible to provide a highly compressed animation stream. Within a dedicated modeling approach — the so-called MeshGrid — we show how the bone and muscle-based animation mechanism is applied to deform the 3D space around a humanoid.
Abstract. Classical volume rendering is computed by casting a bundle of parallel rays from a flat viewing plane onto the volume data set, and produces as such a spatially limited view of the objects in the data set. The method described in this paper is able to generate an overall planar view of an object that is topologically compatible with the sphere, by firing rays from a nearby surrounding surface and by unfolding this surface in a 2D plane, without introducing major distortions. It has been devised to facilitate the interpretation of the cerebral cortex. An initial surface consisting of two hemi-ellipsoids, one to cover the top and another one to surround the bottom of the brain, is interactively defined and deformed via a deformable model approach towards a dilated version of the cortical surface of the brain. During deformation, the nodes on the surface are continuously redistributed, to maintain a near homothetic mapping with the plane. Once the surface has converged to the dilated brain surface, rays are casted from the nodes, according to the normal of the surface at the node. The shading result, computed at the intersection of the rays with the original brain surface, is mapped via the near homothetic mapping to the plane. With this approach sulci can be followed in their entirety, so that it is much easier to derive their spatial relationship and to recognize them.
Three classes of statistical techniques used to solve image segmentation and labelling problems are reviewed:(1) supervised and unsupervised pixel classification, (2) exploitation of the probability distribution map as a way to model image structure, (3) Markov Random Field modelling combined with MAP statistical classification. Diverse examples illustrate the potential of the three approaches that are described'as generic methods belonging to a common framework for image segmentatiodlabelling.
This paper describes a surface flattening technique, which has been developed in particular to obtain a complete view of the cortical surface of the brain. However, the method is able to produce an overall planar view of any anatomical or real-life object, provided it is topologically compatible with the sphere (i.e. genus 0). It computes the shading of the original surface for rays casted from a nearby surrounding surface and unfolds this surface in a 2D plane, without introducing major distortions. The flat image consisting of the mapped shading results has the advantage that the sulci (i.e. the grooves characterizing the superficial brain geometry) of the cortical surface of the brain can be followed in their entirety, which facilitates the study and the recognition of their patterns.The new visualization method is integrated into a versatile medical image analysis environment. A first study to assess its usefulness has been accomplished and is also reported in this paper.
The aim is to improve the operability of an advanced demonstration platform incorporating reflexive teleoperated control concepts developed on a mobile robot system. The robot is capable of autonomously navigating in semi-structured environments. Reflexive tele-operation mode employs the robot extensive onboard sensor suite to prevent collisions with obstacles when the human operator assumes control and remotely drives the robot to investigate a situation of interest. For the shared autonomy aspect, four levels of autonomy have been implemented: tele-operation, safe mode, shared autonomy and autonomous mode. The operability level is enhanced by improving significantly the situational awareness of the operator by using an inertial tracker in combination with a head mounted display creating a certain feeling of presence. As such, the system permits precision observation and pinpoint data collection without subjecting the user to a possibly hazardous remote environment.
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