Haptic Rendering - Department of Computer Science

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Nov 14, 2013 (3 years and 11 months ago)

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Haptic Rendering

Comp 259

Jingdan Zhang

31
, Mar, 2004

Haptic Interaction



“… process of applying forces
representing a virtual environment to the
user of a haptic interface, or force
-
feedback device”


Goal of haptic rendering


Enable a user to touch, feel and
manipulate virtual o
b
jects


Enhance a user’s experience in a
synthetic environment


Provide a natural intuitive interface


Applications of Haptics


Entertainment


Education and training


Scientific visualization


Surgical simulation


Robot
-
assisted surgery




Tele
-
operation




Cooperative Manipulation


Human Haptics


Two complementary channels:



Tactile


Strictly responsible for the variation of the
cutaneous stimuli


Presents spatial distribution of forces



Kinesthetic



Refers to the human perception of one’s
own body position and motion


Presents only the net force information


Main components


Haptic interface


Electro
-
mechanical system


Graphical objects


Contain shape and other property


Haptic rendering algorithm


Joins the first two components

Haptic interface

Sensable Technologies Inc.

PHANTOM Desktop

Virtual Technologies Inc.

Cyber Force

Immersion co.

Impulse stick

Haptic rendering algorithm


Two parts:
Collision detection, collision response


Example: Hard sphere



























s
u
s
u
s
u
s
u
s
u
s
u
z
z
y
y
x
x
r
r
z
z
y
y
x
x
r
r
r
R
k
R
r
F
1
ˆ


)
(
)
(
)
(
otherwise

ˆ
)
(



0

2
2
2
Collision Detection


Computationally fast collision detection:
update rate 1KHz


H
-
COLLIDE

[
Gregory

et al. 1999]


Spatial Decomposition


Bounding Volume Hierarchy based on OBBTrees


Frame
-
to
-
Frame Coherence


Sensation preserving simplification

[Oaduy &
Lin, 2003]


Multiresolution representation

The models of the probe

a line segment

a point

a 3D object

Handle the collision:
Penalty methods


Determine the feedback force
directly from penetration depth


Subdivide the object volume and
associate each a sub
-
volume with
each surface





Work well for simple objects

Limitations of penalty
methods

Lack of locality

Force discontinuity

“Pop
-
Thru” of thin Object

Handle the collision:
Constrained based method


Constrain a virtual proxy of the
haptic interface to ramain on the
surfaces


Gold object [Zilles et al. 1997]


Virtual Proxy [Ruspini et al. 1997]


IHIP & HIP [Ho et al. 1999]

Virtual Proxy(1)

Virtual Proxy(2)

,
ˆ




,
ˆ


,
ˆ


ubject to


minimize
3
2
2
1
1
a
x
n
a
x
n
a
x
n
s
p
x
T
m
T
T





Surface properties


Normal


Contact Impedance


Friction


Texture

Force Shading


Render object surfaces as smooth and
continuous, even when the underlying
representation is not


Analogous to Phong Shading

Contact Impedance


Happening when user contact the
surface


Perpendicular to the surface


Spring force and
viscous

damping force

Bv
Kx
f


Friction


Happening when user stroke the
surface


The lateral force, opposite to motion


The function of the coefficient of
friction and normal force


Coulomb friction: static and dynamic
friction

Texture


Varied ways to represent and
display texture


Deterministic textures


Stochastic Models


Haptic recordings

Lateral
-
force gradient
algorithm(1)


Minsky’s PhD thesis 1995


Texture is represented as 2D height
field


2 DOF, render the texture as
tangential vibration force


Assume the surface is frictionless

Lateral
-
force gradient
algorithm(2)

Moving from
x
1

to
x
2
:

Δ
PE = work = F*D


At the same time:

Δ
PE = PE
2
-
PE
1


= (l
1



l
2
)mg


So:

F = mgtan
θ

What new?


Haptic rendering of interaction
between textured objects
[Otaduy,
Jain, Sud, Lin 2004]


Use texture (height field) to encode
surface details


A new force model


Fast calculation of directional
penetration depth( Implement on GPU)

Preprocessing

Rendering pipeline


Step1: Perform collision detection at
each step. Determine pairs of
contact points and penetration
directions based on coarse model.


Step2: Calculate the force and
torque for each contact based on
texture.


Step 3: Compute the net force and
torque.

Penetration depth

Intersection
of A & B

Global penetration


depth


Directional

penetration


depth

n

along
n

Penetration depth of height
field

))
,
(
)
,
(
(
max
)
(
)
,
(
v
u
h
v
u
h
B
A
D
D
v
u
n
B
A





Calculate height function on
surface

u

v

n

Flatten

Approximate

Height Function

The force model(1)


Penalty
-
based force, defined as
elastic potential field

2
2
1

k
U


Define force
F
and torque
T
as

)
(















k
U
T
F
)
,
,
,
,
,
(
z
y
x
z
y
x

















The force model(2)


In the local reference system
{
u
,
v
,
n
}

T
n
n
v
n
u
n
n
n
n
T
n
v
u
n
v
u
v
u
k
T
T
T
F
F
F
)
,
,
,
1
,
,
(
)
,
,
,
,
,
(






















In the global reference system

F
c
p
T
T
T
n
v
u
T
F
F
F
n
v
u
F
T
n
v
u
T
n
v
u





)
(
)
,
,
)(
,
,
(
)
,
,
)(
,
,
(
The force model(3)


The partial derivatives

u
n
v
u
u
n
v
u
u
u
n
v
u
n
n
v
u
n
n









2
)
,
,
,
,
,
(
)
,
,
,
,
,
(
,











can be obtained by
translating the object
Δ
u along the
u

axis and computing the directional
penetration depth

,...)
(
u
u
n



Experiment result

Textured blocks

File and CAD part

Hammer and torus

Block and gear

Stochastic models(1)


What is texture?



From observation


an image that looks approximately the
same, to humans, from neighborhood to
neighborhood


From stochastic view



multidimensional signal obeying some
statistical properties


Stochastic models(2)


Basic assumption:


the feedback forces from texture can
be represented as stochastic models


Several models:


Gaussian distributions


Markov random field


Stochastic input parameters derived
by analyzing actual force data

The Gaussian distribution


The roughness of many surface can
be approximated as Gaussian:


)
,
(
2


Normal
A Stochastic Approach(1)


Siira & Pai 1996


For texture rendering, it is suffice to
give the correct psychological
illustration


Two assumptions


Normal force is proportional to the
height of the asperities


Lateral texture forces is proportional to
the normal force


A Stochastic Approach(2)


If user is in contact and moving
tangential to the surface, calculate
texture output









otherwise

1
for

0
)
,
(
~
2
texture
texture
friction
constraint
contact
texture
texture



v
u
uNormal
F
F
F
F
F
F
F
Haptic recordings


Analogous to image
-
based rendering


Pre
-
sampling the forces occurring at different
location


Play them back in the simulation


Two sources


From off
-
line physical
-
simulation


To reduce the real time computation burden


From real world texture


To avoid the modeling complexity


Challenge


How to parameterize the recorded forces




Conclusion


Haptic rendering is cool. You can
not see, but you can feel.



It is the next frontier for CG
research.


References


Allison Okamura. "Haptics for Virtual Reality." Course note.
http://www.me.jhu.edu/~allisono/courses/
530.651/lectures/lecture09.pdf


Basdogan, C., Srinivasan, M.A. "Haptic rendering in virtual
environments." network.ku.edu.tr/~cbasdogan/
Tutorials/VRbookChapter.pdf


Gregory A., Lin M., Gottschalk S. and Taylor R. "H
-
Collide:
A Framework for Fast and Accurate Collision Detection for
Haptic Interaction." In the Proceedings of IEEE Virtual
Reality Conference 1999.


Ho,C.H., Basdogan,C., and Srinivasan, M. A. 1999.
"Efficient point
-
based rendering techniques for haptic
display of virtual objects." Presence 8, 5, pp.477
-
491.


Juhani Siira, Dinesh K. Pai, "Haptic Texturing
-

A
Stochastic Approach
.
", IEEE International Conference on
Robotics and Automation, 557
-
562, Minnesota, 1996.


Max Smolens. "Haptic Rendering." Course Note.
http://www.cs.unc.edu/~lin/COMP259
-
S03/LEC/20a.ppt

References(2)


Miguel A. Otaduy and Ming C. Lin, "Sensation Preserving
Simplification for Haptic Rendering." In Proceedings of ACM
SIGGRAPH 2003 / ACM Transactions on Graphics, Vol. 22. pp.
543
-
553. San Diego, Ca. 2003.


Miguel A. Otaduy
, Jian, Sud
and Ming C. Lin, "Haptic Rendering
of Interaction between Textured Models." Submitted to ACM
SIGGRAPH 2004.


Minsky, M. 1995. "Computational Haptics: The sandpaper
system for synthesizing texture for a force
-
feedback display."
PhD thesis, Ph.D. Dissertation, Program in Media Arts and
Sciences, MIT.


Ruspini, Kolarov and Khatib. “The haptic display of complex
graphical environments.” Proc. ACM SIGGRAPH 1997.


Zilles, C.B. and Salisbury, J.K. “A constraint
-
based god
-
object
method for haptic display.” Proc. IEE/RSJ International
Conference on IntelligentRobots and Systems, Human Robot
Interaction, and Cooperative Robots, Vol. 3, p. 146
-
151, 1995.


Salisbury, J.K. et al. “Haptic rendering: programming touch
interaction with virtual objects.” Proc. ACM SIGGRAPH 1995.



Thank you.