Introduction to Computer Haptics

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Introduction to Computer Haptics

• Chris Harding
• charding_at_iastate.edu

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Haptic (adj.) (from the Greek word haptesthai for
to grasp or to touch) related to the sense of
touch.
Graphical Rendering process of displaying
synthetically generated 2D/3D visual stimuli to
the user
Haptic Rendering process of displaying
synthetically generated 2D/3D haptic stimuli to
the user
Motors, cables, actuators, position sensors,
End-effector (pen, thimble, surgical instrument,
)
simulated haptic probe
Haptic Interface device for touch interactions
in real and virtual worlds
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Human vs Machine Haptics
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Machine Haptics
Types of Haptic Devices
Tactile Displays (skin)
Force feedback Displays (Kinesthetic position)
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Types of Haptic Devices
Active
Passive
keyboard, trackball, mice, etc.
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Types of Haptic Devices
Grounded
Attached
Hulk strong crush Coke can !!
combined
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Applications
Haptic Feedback for Molecular Simulation
Haptic Feedback for Medical Simulation and
Training
force
molecule
Haptic Display
Visual Display
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Applications
Haptic Visualization
Haptic Feedback for Collaborative Engineering
Design
haptic display
collected data
tangible data

• Tangible Interfaces
• buttons
• dials
• slider bars
• folders
• layers
• force fields

Simulation of repair and maintenance tasks
Haptic User Interface (HUI)
Haptic Feedback for Crew Training
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• Geometry
• Color
• Stiffness
• Deformability

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Point-based Haptic feedback

• Problem
• simulating the Human hand (22 DOF) and tactile
  sensations (skin pressure) is very difficult
  (impossible) to simulate
• Need very fast update rates (1000 Hz)
• Need Interface acceptable to everyday users
• Affordable, with API for non-haptic specialists
• Solution (Enter the PHANtOM)
• Use only a single point (3DOF)
• point with stylus (direction vector)
• GHOST API, ReachIn API, OpenHL

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Virtual Finger Tip
Stylus Tip
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Haptic Rendering with a Force Display
virtual wall
F stiffness dist
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point-object interaction
HIP Haptic Interface Point True (real world)
position of stylus tip Hand always drawn outside
the sphere
Assumption Stiffness 1.0
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Haptic Rendering of 3D Objects via Proxy
(point-object interaction)
d Proxy to Tipdistance
HIP (stylus tip actual position!)
F k d (Hookes Law)
Spring with stiffness k
Proxy (displayed position)
(If in doubt the visual sense will override the
sense of touch )
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Haptic Rendering of Polygonal Surfaces
HIP actual tip position IHIP Proxy point
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Haptic Display of Surface Details

• Haptic smoothing of object surfacesding)(similar
  to Phong shag
• Rendering of haptic textures
• Haptic rendering of surfaces with friction (

actual shape
displayed shape
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Haptic Texturing

• image-based

two-stage mapping
Bier Sloan, 1986

• procedural

bump mapping
h(x,y,z)
Blinn, 1978 Max and Becker, 1994
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Force-Reflecting Deformable Models
Surgical Simulation
F
F
Haptic Sculpting/painting
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Reachin Display

• Phantom Reachin Display Reachin API
• 3D stereo via mirror
• Integrates 3D Vision with haptics
• After calibration real stylus virtual stylus
• Uses proxy method
• 3D haptic user interface (HUI)
• API define VRML scenegraph with graphics and
  haptics properties

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Sensable Omni Phantom

• New, cheap version of phantom line
• Stiffness 3 - 4 N
• Firewire port
• Windows, Linux (?)
• OpenHL API (low-level OpenGL-like haptics)
• Demo of virtual clay sculpting (splodge?)

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Conclusion

• Point haptics Reduction of hand to point
• Separate Update loop at 1000 Hz
• Same geometry as graphics but additional haptic
  properties
• Improvements in tool based interaction
• Surgical simulation and training
• assembly/repair planning
• Virtual clay sculpting (art, rapid prototyping)
• Sculpting of subsurface layers (saltdome
  modelling)