Collision detection

Virtual reality applications refer to the use of com- puters to simulate a physical environment in such a way that humans can readily visualize, explore, and interact with "objects" in this environment. The design of virtual scenes requires realistic physically based simulation algorithms and in particular effi- cient collision detection routines. Collision detection prevent penetrations between objects. This paper presents an overview of the collision detection procedures for rigid bodies. It divides those procedures in two families that form a general hybrid collision detection algorithm. The first family is used in the first phase known as broad phase that roughly detects collision. The second family is used in the second one known as narrow phase that exactly detects if collision occurs.

This paper describes a fast technique for dressing virtual humans with different pieces of clothing. It exploits a mass-spring cloth model but applies a new velocity modification approach to overcome its super-elasticity. The algorithm for cloth-body collision detection and response is based on image-space interference tests, unlike most of the existing ones, which use objectspace checks. The modern workstations ’ graphics hardware is used not only to compute the depth maps of the body contours but also to interpolate the body normal vectors. As a result the approach is very fast and makes it possible to sew a garment around a virtual human body in about a second.

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

This research work seeks to address collision handling, mainly the safety of humans in a robot work-cell and the avoidance of collision between the robots and any obstacle as this may lead to severe injuries if a robot collides with a human. Also collision detection and avoidance for industrial robots in harsh environments (e.g. explosive environments found in oil and gas sector) to avoid a potential accident that can also damage robots and other equipment in the environment. This research builds on the concept builds on collision detection and aims at enabling the robot to find a collision free path bypassing the obstacle and leading to the target position using different sensors.
A simulator would be used here called Robotstudio simulator which is a 3D teaching demo, illustrating collision detection in a work cell.
The Mobotsim which is an open source software is used to detect obstacles within a work cell and the Robotstudio simulator would demonstrate how this obstacle is detected and avoided by industrial robots.

Designing a robot physically and validating it at every step is an arduous task. Contemporary robotics simulators can help to achieve laborious physics simulations, 3D visualizations, virtual robot modeling and novel research work that save time and money. Simulators are written in numerous programming languages like C, C++, Java, C# and other OOP languages that decide their platform compatibility. Some robot simulators use physics engines like ODE, Karma Engine for better simulation that include responses like collision detection, scene representation and rigid body simulations. Some use sophisticated 3D graphic aids like OpenGL and Graphic cards (NVidia, ATI) rather than traditional Direct3D, considering various facets like cost, portability and extensions. Codes can be transferred to the real robots from some simulators after proper verification for their operation. Unlimited features like multiplayer, controllers transference over networks, `special effects' and so forth, keep on pouring. This paper proffers some of the widespread commercial/ open-source simulators for robots and UAVs used in market. Further, I conclude that any kind of robot including legged, wheeled or UAVs can be simulated using simulators available in market with continuous endeavors to upgrade these simulators.

An important geometric and linear algebraic problem denoted as vector orthogonalization, fundamental
to handle contact detection and contact force descriptions in engineering applications, is here considered.
The problem is to find a set of linearly independent vectors that span the entire R3 Euclidean space given
only one of the base vectors. This paper contains the explanation on how the Householder transformation,
which is extensively used for matrix orthogonalization, provides an elegant analytical expression that
solves the vector orthogonalization problem. Based on the QR matrix factorization method, the orthogonal
vectors are produced using a Householder reflection that transforms the given vector into a multiple of
the unit vector whose entries are all zero with the exception of the first. Based on efficiency, accuracy
and numerical robustness criteria, the proposed technique is compared to other vector orthogonalization
methods. The numerical results show that the Householder vector orthogonalization formula is the most
efficient when it comes to outputting a set of orthonormal vectors, presenting speedups close to 1.017
times faster when compared to other efficient techniques. In addition, when dealing with Cn continuous
implicit surfaces, with n > 1, the Householder vector orthogonalization formula reveals to be particularly
useful for vector calculus since it provides a set of differential operators to calculate, not only the normal,
but also the tangent and binormal surface vector fields which can be used to calculate surface curvatures.
The major contribution of this paper is to explicitize how the Householder transformation holds an
analytical expression that calculates the tangent and binormal vectors from a given normal at a surface
point vector, which is computationally efficient and numerically robust for real-time computational
geometry and computer graphics applications, namely, for contact mechanics applications with implicit
surfaces of engineering problems with multiple contacts. Such a vector orthogonalization technique also
has direct applications in several CAD/CAM processes, ranging from the elaboration of rough solid models
to the precise manufacturing of a product.

Bounding volume hierarchies are widely employed in many areas of computer graphics. Usually they are used as crude approximations of the scene geometry to speed up some time-consuming computations, such as visibility tests for frustum culling, ray shooting, collision detection, etc. A number of bounding volume types have been discussed by various researchers. They include bounding spheres, axis-aligned and oriented bounding boxes, and others. Although it is practically possible to use any of these bounding volumes, some types prove to be particularly useful in certain applications, e.g. Gortschalk et al. (1996) used oriented bounding boxes to implement a very effective exact collision detection scheme. The authors address the problem of efficient bounding volume selection, the solution of which allows one to significantly accelerate such operations as visibility tests for frustum culling, collision detection and ray shooting. They prove that minimal surface area (perimeter in 2D) oriented bounding box is optimal among all the oriented bounding boxes with respect to the three operations stated above. Then, they develop a number of algorithms to create optimal oriented bounding boxes and their approximations and finally discuss the results of the practical implementation

The Eastern Anatolian Plateau emerges from the continental collision between Arabian and Eurasian plates where intense seismicity related to the ongoing convergence characterizes the southern part of the plateau. Active deformation in this zone is shared by mainly thrust and strike-slip faults. The Özyurt thrust fault and the Gülsünler sinistral strike-slip fault are newly determined fault zones, located to the north of Van city centre. Different types of faults such as thrust, normal and strike-slip faults are observed on the quarry wall excavated in Quaternary lacustrine deposits at the intersection zone of these two faults. Kinematic analysis of fault-slip data has revealed coeval activities of transtensional and compressional structures for the Lake Van Basin. Seismological and geomorphological characteristics of these faults demonstrate the capability of devastating earthquakes for the area.

Computer aided Finite Element Analysis (FEA) tools have been used since the late 1950's. The asynchronous plot of simulations and the corresponding results consumes a large amount of engineering cycle time; additionally, applying FEA parameters on a 3D CAD model with 2D mouse/keyboard has always been a complex process. This paper presents the prototype of a software toolkit that performs real-time FEA simulations, the software is associated with Virtual Reality (VR) technologies which gives users a better sense of spatial presence. Interactive product design and real-time FEA is discussed in this paper.

In this paper a method for generating Oriented Bounding Boxes (OBB) using genetic algorithms (GA) is proposed. OBBs are used in a hierarchy of bounding volumes to detect collisions between objects. Currently, the most used method for generating OBBs is based on the covariance matrix (CV) of the points of the model, but it has many flaws and in most cases does not find the optimum OBB. We performed several tests with
both methods (CV vs. GA). Generally the GA method provides a better adjustment of the OBB to the geometry of the models than the CV method. The metric used for measuring the adjustment of the OBB was the volume of the OBB. The time required for performing the collision detection was also tested, obtaining better results with the GA method. It is suggested to use the GA method when the models are rigid and will not be deformed.