Crane collision modelling using a neural network approach

The objective of the present work is to find a Collision Detection algorithm to be used in the Virtual Reality crane simulator (UVSim®), developed by the Robotics Institute of the University of Valencia for the Port of Valencia. The method is applicable to box-shaped objects and is based on the relationship between the colliding object positions and their impact points. The tool chosen to solve the problem is a neural network, the multilayer perceptron, which adapts to the characteristics of the problem, namely, non-linearity, a large amount of data, and no a priori knowledge. The results achieved by the neural network are very satisfactory for the case of box-shaped objects. Furthermore, the computational burden is independent from the object positions and how the surfaces are modelled; hence, it is suitable for the real-time requirements of the application and outperforms the computational burden of other classical methods. The model proposed is currently being used and validated in the UVSim Gantry Crane simulator

Enaction and Visual Arts : Towards Dynamic Instrumental Visual Arts

International audienceThis paper is a theoretical paper that presents how the concept of Enaction, centerd on action and interaction paradigm, coupled with the new properties of the contemporary computer tools is able to provoke deep changes in arts. It examines how this concept accompanies the historical trends in Musical, Visual and Choreographic Arts. It enumerates the new correlated fundamental questions, scientific as well as artistic, the author identifies. After that, it focuses on Dynamic Visual Arts, trying to elicit the revolution brought by these deep conceptual and technological changes. It assumes that the contemporary conditions shift the art of visual motion from a ''Kinema'' to a ''Dyname'', allowing artists ''to play images'' as ''to play violin'', and that this shift could not appear before our era. It illustrates these new historical possibilities by some examples developed by the scientific and artistic works of the author and her co- workers. In conclusion, it assumes that this shift could open the door to a new genuine connection between arts that believed to cooperate but that remained separated during ages: music, dance and animation. This possible new ALLIANCE could lead the society to consider a new type of arts, we want to call ''Dynamic Instrumental Arts'', which will be really multisensorial: simultaneously Musical, Gestural and Visual

Physiologically-based Modeling and Visualization of Deformable Lungs

A real-time physiologically-based breathing model of lungs under normal and pathological scenario has been conceived and implemented. The algorithm developed for lung deformations under various breathing scenarios uses polygonal models of lungs. The method developed avoids the “stiffness” problem observed in Mass-Spring models. Hardware acceleration of the exhalation and the inhalation process is done using vertex shaders. The method of deformation is general and can be applied to any lung model

Collision response analysis and fracture simulation of deformable objects for computer graphics

Computer Animation is a sub-field of computer graphics with an emphasis on the time-dependent description of interested events. It has been used in many disciplines such as entertainment, scientific visualization, industrial design, multimedia, etc. Modeling of deformable objects in a dynamic interaction and/or fracture process has been an active research topic in the past decade. The main objective of this thesis is to provide a new effective approach to address the dynamic interaction and fracture simulation. With respect to the dynamic interaction between deformable objects, this thesis proposes a new semi-explicit local collision response analysis (CRA) algorithm which is better than most of previous approaches in three aspects: computational efficiency, accuracy mid generality. The computational cost of the semi-explicit local CRA algorithm is guaranteed to be O('n') for each time step, which is especially desirable for the collision response analysis of complex systems. With the use of the Lagrange multiplier method, the send-explicit local CPA algorithm avoids shortcomings associated with the penalty method and provides an accurate description of detailed local deformation during a collision process. The generic geometric constraint and the Gauss-Seidel iteration for enforcing the loading constraint such as Coulomb friction law make the semi-explicit local CRA algorithm to be general enough to handle arbitrary oblique collisions. The experimental results indicate that the semi-explicit local CRA approach is capable of capturing all the key features during collision of deformable objects and matches closely with the theoretical solution of a classic collision problem in solid mechanics. In the fracture simulation, a new element-split method is proposed, which has a sounder mechanical basis than previous approaches in computer graphics and is more flexible to accommodate different material fracture criteria such that different failure patterns are obtained accordingly. Quantitative simulation results show that the element-split approach is consistent with the theoretical Mohr's circle analysis and the slip-line theory in plasticity, while qualitative results indicate its visual effectiveness

Physically Based Mesh-free Deformation Framework and Techniques for Computer Graphics

In this thesis, we introduce a mesh-free deformation framework. Four different applications are presented based on it. Among them, a technique of mesh-free deformations and a technique ofreusable deformations are to model the deformations in two different ways, while the hyper-twist and the force mapping are applied to other graphic purposes related to deformations.Existing physicanv-based deformation techniques, such as the finite element method and the massspring systems, require the deformed object to be properly meshed. The proposed mesh-free deformations are constructed with unconnected points and no mesh is required in the computation.This process strict~1' follows the principles of classic mechanics and a deformation is defined as a combination of fundamental solutions. Because no mesh is involved, deforming a complex shape is as straightforw'ard as deforming a simple one and the trade-off between efficiency and accuracy is easy to achieve by redistributing the points concerned. Experiments show that this method is fast and offers similar accuracy to the finite element methods.Reducing both computational cost and amount of unnecessary human intervention remains a pressing issue in the animation production. To provide a faster and more user-friendly tool, we extend the above mesh-free deformations technique and develop another technique. A key feature is thereusability of deformations. Existing deformations can be simply extracted and reapplied physicallyusing the 'copy' and 'paste' operations. it relieves the modelling efforts. In this way, the visual realism is combined with the modelling efficiency and the user-friendliness for animators.The mesh-free deformation framework is capable to describe the deformations in an infinite body which is in line with the distortion of a 3D space. The twist of an infinite body, hyper-twist, is investigated to show how a 3D space and the object embedded can be radically deformed. Abstract shapes with aesthetic effects can be created in this process as well as their animations. Following the idea of mesh-free computation, we apply forces on a surface to create the fine details of the surface. A force map records the applied forces and their distributions. We call this technique force mapping, which can be used for surface modeling, compression, reconstruction and editing. As an alternative to displacement mapping, force mapping benefits from the fact that the physical property, force, is integrated into a geometric surface explicitly

Efficient collision detection for real-time simulated environments

Thesis (M.S.)--Massachusetts Institute of Technology, Program in Media Arts & Sciences, 1994.Includes bibliographical references (leaves 64-68).by Paul Jay Dworkin.M.S