Interaktive Montageplanung mit Kollisionserkennung

Effiziente Methoden zur Kollisionserkennung sind nicht nur bei der Montage— und Robotersimulation von Bedeutung, sondern ganz allgemein bei der Simulation mechanischer Vorgänge. Sie bilden die Voraussetzung für die Simulation der Dynamik eines Mechanismus. Diese Arbeit zeigt neue Wege zu einer effizienten Kollisionskontrolle und zu ihrer Anwendung im Zusammenhang mit der Montageplanung.Liegt nicht vor

Interaktive Montageplanung mit Kollisionserkennung

Effiziente Methoden zur Kollisionserkennung sind nicht nur bei der Montage— und Robotersimulation von Bedeutung, sondern ganz allgemein bei der Simulation mechanischer Vorgänge. Sie bilden die Voraussetzung für die Simulation der Dynamik eines Mechanismus. Diese Arbeit zeigt neue Wege zu einer effizienten Kollisionskontrolle und zu ihrer Anwendung im Zusammenhang mit der Montageplanung.Liegt nicht vor

Motion Correction for Separate Mandibular and Cranial Movements in Cone Beam CT Reconstructions.

BACKGROUND Patient motions are a repeatedly reported phenomenon in oral and maxillofacial cone beam CT scans, leading to reconstructions of limited usability. In certain cases, independent movements of the mandible induce unpredictable motion patterns. Previous motion correction methods are not able to handle such complex cases of patient movements. PURPOSE Our goal was to design a combined motion estimation and motion correction approach for separate cranial and mandibular motions, solely based on the 2D projection images from a single scan. METHODS Our iterative three-step motion correction algorithm models the two articulated motions as independent rigid motions. First of all, we segment cranium and mandible in the projection images using a deep neural network. Next, we compute a 3D reconstruction with the poses of the object's trajectories fixed. Third, we improve all poses by minimizing the projection error while keeping the reconstruction fixed. Step two and three are repeated alternately. RESULTS We find that our marker-free approach delivers reconstructions of up to 85% higher quality, with respect to the projection error, and can improve on already existing techniques, which model only a single rigid motion. We show results of both synthetic and real data created in different scenarios. The reconstruction of motion parameters in a real environment was evaluated on acquisitions of a skull mounted on a hexapod, creating a realistic, easily reproducible motion profile. CONCLUSIONS The proposed algorithm consistently enhances the visual quality of motion impaired CBCT scans, thus eliminating the need for a re-scan in certain cases, considerably lowering radiation dosage for the patient. It can flexibly be used with differently sized regions of interest and is even applicable to local tomography. This article is protected by copyright. All rights reserved

Rolling Rigid Objects

Simulating the dynamics of rigid bodies plays plays an important role in virtual reality applicationssuch as virtual assembly planning an ergonomy studies but also in the field of computer animation. In order to decrease the complexity of the objects with curved surfaces directly instead of apprioximating them by polyhedra. One important aspect of the dynamic bahavior of objects with curved surfaces is the rolling process. In this paper we develop the dynamics equations that describe the rolling motion of arbitrarily shaped rigid objects that are in a one- or two-point contact with an arbitrary surface. as a method to keep track of pairs of closest points we use techniques form differential geometr

Dynamic Collision Detection in Virtual Reality Applications

We present data structures and algorithms for dynamic collision detection in virtual reality (VR) applications. The methods are applicable to all general polygonal models. They combine the advantages of collision detection using bounding volume (BV) hierarchies with the ability to compute dynamic collision detection results. The results are used as input for further simulations, e.g. contact or dynamics simulation. First we present new methods to compute BV hierarchies using optimization goals which can also be used to improve known computation methods. Second we show how to integrate BV hierarchies into a process of dynamic collision detection, so that the bounding objects as well as the surface patches of the objects are tested for overlap during their motions. The performance of the techniques is shown by means of a tting simulation in the automotive industry