Manipulation of Virtual Objects

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14 Νοε 2013 (πριν από 3 χρόνια και 11 μήνες)

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Graduate Programs in Computer Science

http://www.cs.utsa.edu

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

Jan 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.

Graduate Programs in Computer Science

http://www.cs.utsa.edu

Outline


Background


Introduction


Related Work


System Design


Results and Discussion


Conclusions


Future Work

Graduate Programs in Computer Science

http://www.cs.utsa.edu

Background


What is VR?


Virtual Reality



Applications of VR


Video Games


Training Systems


Simulator


3D/4D Movies, Games


Auto Design




Graduate Programs in Computer Science

http://www.cs.utsa.edu

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.

Graduate Programs in Computer Science

http://www.cs.utsa.edu

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.

Graduate Programs in Computer Science

http://www.cs.utsa.edu

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.


Graduate Programs in Computer Science

http://www.cs.utsa.edu

Introduction


Real World Grasping


Increasing contact area with increasing contact force.

Left: loose touch.

Right: strong pressure between finger and a pane of glass.

Graduate Programs in Computer Science

http://www.cs.utsa.edu

Introduction


Physics problem


f =
μ
N


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


Graduate Programs in Computer Science

http://www.cs.utsa.edu

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.


Graduate Programs in Computer Science

http://www.cs.utsa.edu

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].

Graduate Programs in Computer Science

http://www.cs.utsa.edu

System Design


Software Architecture



Tracking



Hand Model


Graduate Programs in Computer Science

http://www.cs.utsa.edu

System Design


Software Architecture


Scenegraph System: OpenSG


Physics Engine: bullet


User Input

Graduate Programs in Computer Science

http://www.cs.utsa.edu

System Design


Tracking


An optical finger tracking system


Seven evenly spread cameras for a 3m
3

volume

Graduate Programs in Computer Science

http://www.cs.utsa.edu

System Design


Hand Model


A rigid body (grey)


A soft body (green)


Graduate Programs in Computer Science

http://www.cs.utsa.edu

Results and Discussion


Unconstrained interaction with a horse model. The fingerpads adapt to the
geometries’ shape, enabling stable and robust interaction.

Graduate Programs in Computer Science

http://www.cs.utsa.edu

Results and Discussion


Two handed interaction with non
-
constrained objects. Collision response
between torus and stick is enabled through physics simulation.

Graduate Programs in Computer Science

http://www.cs.utsa.edu

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.

Graduate Programs in Computer Science

http://www.cs.utsa.edu

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



Graduate Programs in Computer Science

http://www.cs.utsa.edu

Future Work


A soft body for palm



Using different deformation algorithm depending on the
situation



A skinned hand representation

Graduate Programs in Computer Science

http://www.cs.utsa.edu

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.

Graduate Programs in Computer Science

http://www.cs.utsa.edu

Thank you!


Questions?