A Soft Hand Model for Physically-based Manipulation of Virtual Objects

Graduate Programs in Computer Sciencehttp://www.cs.utsa.edu

A Soft Hand Model for Physically-based Manipulation

of Virtual ObjectsJan Jacobs

Group Research Virtual Technologies

Volkswagen AG

Bernd Froehlich

Virtual Reality Systems Group

Bauhaus-Universitat Weimar

In Virtual Reality Conference (VR), 19 - 23 March, 2011 Singapore, IEEE, 2011.


Outline Background

Introduction

Related Work

System Design

Results and Discussion

Conclusions

Future Work


Background What is VR?

Virtual Reality

Applications of VR Video Games Training Systems Simulator 3D/4D Movies, Games Auto Design


Background The integration of physical behavior has significantly increased the

quality of games and virtual environments overall

The interaction with simulated objects also needs to occur on a physical basis.

The representation of a user in the virtual world needs to be physically modeled to achieve a realistic interaction between user and virtual objects.

The problem: the modeling of the finely articulated human hand to enable finger-based interaction.


Introduction A direct and robust finger-based manipulation relies on three major

issues Stable grasping of objects Robust manipulation Controlled releasing of objects.

In general, there are two common ways to achieve these goals Grasping through heuristics Collision based physical simulations.


Introduction In 2005, Borst et al. [1] relies on a hand

model constructed from rigid bodies.

Problems: It could not correctly consider friction

between fingers and virtual It required careful tuning of parameters for a

reasonably stable interaction.


Introduction Real World Grasping

Increasing contact area with increasing contact force. Left: loose touch. Right: strong pressure between finger and a pane of glass.


Introduction

Physics problem f = μN μ is the friction coefficient N is the pressure The friction doesn’t related to the contact area

VR Simulation No haptic system Mapping: the higher the pressure, the bigger the contact area


Introduction

A soft body model for each finger phalanx was introduced to enable pressure-based deformation of the soft finger contact areas.

The system allows for very precise and robust finger-based grasping, manipulation and releasing of virtual objects in real-time.


Related Work This idea is originally from Duriez et al. in 2008 [2]. They addressed this

problem by directly calculating friction at skin level. Complexity

The FastLSM algorithm by Rivers et al. [3].

http://www.alecrivers.com/fastlsm/


System Design Software Architecture

Tracking

Hand Model


System Design Software Architecture

Scenegraph System: OpenSG Physics Engine: bullet User Input


System Design Tracking

An optical finger tracking system Seven evenly spread cameras for a 3m3 volume


System Design Hand Model

A rigid body (grey) A soft body (green)


Results and Discussion Unconstrained interaction with a horse model. The fingerpads adapt to the

geometries’ shape, enabling stable and robust interaction.


Results and Discussion Two handed interaction with non-constrained objects. Collision response

between torus and stick is enabled through physics simulation.


Results and Discussion Interaction within an immersive display system. A user interacts with a

constrained steering wheel using both hands, thus reproducing a real-world interaction.


Conclusions A new hand model is based on soft bodies coupled to a

rigid body hand skeleton Precise and robust finger-based grasping, manipulation and

releasing Dynamic adaptation of the stiffness values The implicit friction model

The pressure-based increasing and decreasing of the contact area of the simulated finger phalanxes


Future Work A soft body for palm

Using different deformation algorithm depending on the situation

A skinned hand representation


References [1] C. W. Borst and A. P. Indugula. Realistic virtual grasping. In Virtual Reality

Conference (VR), 2005 IEEE, pages 91–98, 320, 2005.

[2] C. Duriez, H. Courtecuisse, J. P. de la Plata Alcalde, and P.-J. Bensoussan. Contact skinning. In Eurographics 2008 (short paper), pages 313–320, New York, NY, USA, 2008.

[3] A. R. Rivers and D. L. James. FastLSM: Fast lattice shape matchingfor robust real-time deformation. ACM Transactions on Graphics (Proc. SIGGRAPH 2007), 26(3):82, July 2007.


Thank you!

Questions?

A Soft Hand Model for Physically-based Manipulation of Virtual Objects

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