News

Oct, 2017: EUROVR association is co-financing an important initiative: the VR Tour. Organized by Laval Virtual, the tour is scheduled to visit the various actors operating in the fields of Virtual and Augmented Reality in all Europe.

Jun 17, 2017: Haptic and hand tracking demos at the Open Campus 2017.

Feb-Apr 2017: David Vilela (Mechanical Engineering Laboratory, University of Coruna, Spain) visited our lab. He is working on benchmarks to compare different intersection calculation methods in collisions, and also different force models.

Feb 2017: G. Zachmann and J. Teuber visited the Mahidol University in Bangkok, Thailand as part of a delegation from the University of Bremen. The goal of the visit was to foster the cooperation between the two universities and lay ground-work for future colaborations.

Jun 2016: Radio Bremen visited our lab to film the works of the Creative Unit "Intra-Operative Information" for a news magazine on the local TV station. Click here for the film at Radio Bremen. And Click here for the same film on our Website.

May 16, 2016: Patrick Lange was honored with the SIGSIM Best PhD Award at the ACM SIGSIM PADS Conference 2016.

Jun 19-21, 2015: G. Zachmann gives invited talk at the DAAD-Stipendiatentreffen in Bremen, Germany.

Jun 2015: Haptic and hand tracking demos at the Open Campus 2015.

Dec 08-10, 2014: ICAT-EGVE 2014 and EuroVR 2014 conferences at the University of Bremen organized by G. Zachmann.

Sep 25-26, 2014: GI VR/AR 2014 conference at the University of Bremen organized by G. Zachmann.

Sep 24-25, 2014: VRIPHYS 2014 conference at the University of Bremen organized by G. Zachmann .

Feb 4, 2014: G. Zachmann gives invited talk on Interaction Metaphors for Collaborative 3D Environments at Learntec.

Jan 2014: G. Zachmann got invited to be a Member of the Review Panel in the Human Brain Project for the Competitive Call for additional project partners

Nov 2013: Invited Talk at the "Cheffrühstück 2013"

Oct 2013: PhD thesis of Rene Weller published in the Springer Series on Touch and Haptic Systems.

Jun 2013: G. Zachmann participated in the Dagstuhl Seminar Virtual Realities (13241)

Jun 2013: Haptic and hand tracking demos at the Open Campus 2013.

Jun 2013: Invited talk at Symposium für Virtualität und Interaktion 2013 in Heidelberg by Rene Weller.

Apr 2013: Rene Weller was honored with the EuroHaptics Ph.D Award at the IEEE World Haptics Conference 2013.

Jan 2013: Talk at the graduation ceremony of the University of Bremen by Rene Weller.

Oct 2012: Invited Talk by G. Zachmann at the DLR VROOS Workshop Servicing im Weltraum -- Interaktive VR-Technologien zum On-Orbit Servicing in Oberpfaffenhofen, Munich, Germany.

Oct 2012: Daniel Mohr earned his doctorate in the field of vision-based pose estimation.

Sept 2012: G. Zachmann: Keynote Talk at ICEC 2012, 11th International Conference on Entertainment Computing.

Sep 2012: "Best Paper Award" at GI VR/AR Workshop in Düsseldorf.

Sep 2012: Rene Weller earned his doctorate in the field of collision detection.

Aug 2012: GI-VRAR-Calendar 2013 is available!

Inner Sphere Trees for 6-DOF Haptic Rendering

ISTLogo

Inner Sphere Trees () are a novel geometric data structure for approximate collision detection at haptic rates. They support different kinds of queries, namely, proximity queries and a new method for interpenetration computation, the penetration volume in one unified algorithm. In addition, the application does not need to know in advance which situation exists between the pair of objects.

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The penetration volume is related to the amount of water being displaced by the overlapping region and, thus, corresponds to a physically motivated force. It allows us to define a novel penalty-based collision response scheme that provides continuous forces and torques which are applicable to physically-based simulations as well as to haptic rendering scenarios.

The main idea is to bound objects from the inside with a set of non-overlapping spheres. Based on such sphere packings, we construct an "inner bounding volume hierarchy" by extendeding an AI clustering algorithm.

The results show performance at haptic rates both for proximity and penetration volume queries for models consisting of hundreds of thousands of polygons.

Sphere Packing

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In our current implementation of the inner sphere trees, we use a simple heuristic to fill the objects densly with spheres. It is based on discrete distance fields in combination with a greedy sphere creation algorithm that offers a good trade-off between accuracy and speed in practice.

Building the IST

Based on the sphere packing, we create a bounding volume hierarchy. To do so, we use a recursive top-down wrapped hierarchy approach. The partitioning of the spheres is based on a clustering algorithm called batch neural gas with magnification control (i.e., larger spheres get larger weights).

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In the above two screenshots, you can see two levels of the hierarchy (left = first level, right = second level); spheres of the same color belong to the same cluster and, thus, to the same sub-tree.

Contact Forces

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Forces and torques are computed for every pair of overlapping spheres individually. This results in continuous penalty forces and torques, provided the paths of the objects is continuous. This is essential for stable physically-based simulations and haptic rendering.

Download

The ISTs will be integrated into the CollDet-Library in the near future.

Until then, you can send us an email , and maybe we can send you an intermediate version.

Publications

Videos

Click on the pictures to watch the videos.

Overview

This video gives an overview over the ISTs (no audio)

Proximity Queries

Two armadillos Two cows

Penetration Volume

Dragons Screw drivers Two torsos

ISTs in Haptic Environments

Multibody simulation with haptic support Another haptic scene

This work was partially supported by DFG grant ZA292/1-1 and the research project, funded by the Federal Minstry of Education and Research (BMBF) grant Avilus / 01 IM 08 001 U.