Course: Recent Advances in Haptic Rendering and Applications

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Course Recent Advances in Haptic Rendering and
Applications Session IV Rendering of Textures
and Deformable Surfaces Haptic Rendering
ofTextured Surfaces Miguel A.
Otaduy ETH-Zurich http//graphics.ethz.ch/otmigue
l otaduy_at_inf.ethz.ch
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Outline

• Motivation
• Algorithm Overview
• Synthesis of the Force Model
• Penetration Depth on the GPU
• Experiments and Results
• Conclusion

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Introduction
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Introduction

• Geometric surface texture
• Compelling cue to object identity
• Strongly influences forces during manipulation
• Objects with rich surface texture information
  cannot be handled by state-of-the-art haptic
  rendering methods.

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Models
Coarse geometric representations
Haptic textures
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Outline

• Motivation
• Algorithm Overview
• Synthesis of the Force Model
• Penetration Depth on the GPU
• Experiments and Results
• Conclusion

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3-DoF Texture Rendering

• 1 contact point on a textured surface
• Minsky 1995, Ho et al. 1999 high frequency
  forces based on gradient of height field

contact point
height field in texture map
simplified surface
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3-DoF Texture Rendering

• 1 contact point on a textured surface
• Siira and Pai 1996 stochastic model
• Pai et al. 2001 auto-regressive model for
  roughness and friction

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6-DoF Texture Rendering

• Object-object interaction
• Contact cannot be described as point-surface
  contact
• Force and torque output has 6-DoF point contact
  only has 3-DoF
• A different rendering algorithm is required

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Rendering Algorithm

• 1) Compute contact information betweenlow-res
  models

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Rendering Algorithm

• 1) Compute contact information betweenlow-res
  models
• 2) Refine contact information using detail
  geometry stored in textures

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Rendering Algorithm

• 1) Compute contact information betweenlow-res
  models
• 2) Refine contact information using detail
  geometry stored in textures
• 3) Compute contact forces based on novel texture
  force model

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Force Model Overview

• Accounts for important factors identified by
  perceptual studies
• Based on the gradient of inter-object penetration
  depth
• GPU-based computation of directional penetration
  depth

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Outline

• Motivation
• Algorithm Overview
• Synthesis of the Force Model
• Penetration Depth on the GPU
• Experiments and Results
• Conclusion

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Related Work Perception Psychophysics

• Studies on perception of textures through a rigid
  probe by Klatzky and Lederman 1999-present
• Analyze effects of probe diameter, applied force
  and exploratory speed
• Inspiration for our force model

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Roughness Vs. Texture Spacing Klatzky and
Lederman 1999-present
log (roughness)
Probe Diameter (D)Applied Force (F)Exploratory
Speed (v)
log (texture frequency)
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Effect of Probe Diameter (D) Klatzky and
Lederman 1999-present
-
Strong influence of geometry
log (roughness)
D

log (texture frequency)
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Effect of Applied Force (F) Klatzky and
Lederman 1999-present

F
Roughness grows with applied force
log (roughness)
-
log (texture frequency)
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Effect of Exploratory Speed (v) Klatzky and
Lederman 1999-present
Dynamic effects already present in haptic
simulation
v
log (roughness)

-
log (texture frequency)
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Offset Surfaces

• Spherical probe ? trajectory offset surface
• Arbitrary objects ? ???

Use offset surface as descriptor of vibration
How can we generalize offset surfaces?
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Penetration Depth Definition

• Minimum translational distance to separate
  two intersecting objects

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Penetration Depth Definition

• Minimum translational distance to separate
  two intersecting objects

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Directional PD Definition

• Minimum translation along n to separate
  two intersecting objects

n
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Directional PD Definition

• Minimum translation along n to separate
  two intersecting objects

n
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Offset Surface and PD
Offset surface
Textured surface
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Offset Surface and PD
Offset surface
Textured surface
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Offset Surface and PD
penetration depth
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Force Model

• Penetration depth
• Applicable to arbitrary object-object interaction
• Also used in previous single-point rendering
  methods
• Penalty-based potential field

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Force Model

• Determine penetration direction n
• Force and Torque Gradient of energy

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Effect of Geometry

• Force and torque proportional to gradient of
  penetration depthHigh amplitude texture
• ? High derivative of penetration depth
• ? Large force/torque
• Method validated by Minsky 1995

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Effect of Applied Force

• Normal force
• Other forces and torques
• Larger normal force ? Larger roughness effect

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Outline

• Motivation
• Algorithm Overview
• Synthesis of the Force Model
• Penetration Depth on the GPU
• Experiments and Results
• Conclusion

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Directional PD Definition

• Minimum translation along n to separate
  two intersecting objects

n
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Directional PD of Height Fields
B
n
A
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PD with Texture Images
High-res Surface
Low-res Surface
n
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PD with Texture Images
High-res Surface
Low-res Surface
n
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PD with Texture Images
High-res Surface
Low-res Surface
n
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PD with Texture Images
High-res Surface
Low-res Surface
n
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PD Computation Algorithm
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Low-Resolution Models
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Texture Images
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Step 1 Approximate PD
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Step 1 Approximate PD
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Step 2 Refined PD
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Pass 1 Render Geometry
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Pass 1 Texture Mapping
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Pass 1 Sample Surfaces
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Pass 1 Project to PD Direction
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Discrete Height Fields
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Pass 2 Subtract Height Fields
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Pass 2 Copy to Depth Buffer
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Binary Search for Max PD Govindaraju et al.
2004
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Test
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Test
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Gradient of PD
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Gradient of PD

• Central differences
• Recompute PD at 2 new object configurations

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Outline

• Motivation
• Algorithm Overview
• Synthesis of the Force Model
• Penetration Depth on the GPU
• Experiments and Results
• Conclusion

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Experiments

• Offline analysis of force model
• Quality of texture effects
• Performance tests.

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Offline Experiments
u
dn
kh
D
n
v
mh
bh
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Effect of Probe Diameter
Studies by Klatzky and Lederman
Simulation results
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Effect of Applied Force
Studies by Klatzky and Lederman
Simulation results
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Effect of Exploratory Speed
Studies by Klatzky and Lederman
Simulation results
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Roughness under Translation
x
z
y
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Roughness under Rotation
n
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Complex Objects
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Timings File and CAD Part
File full-res 285KtrisFile low-res 632
tris CAD full-res 658KtrisCAD low-res 720tris
Dual Pentium4 2.4GHz NVidia FX5950
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Outline

• Motivation
• Algorithm Overview
• Synthesis of the Force Model
• Penetration Depth on the GPU
• Experiments and Results
• Conclusion

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Summary

• Haptic rendering algorithm usinglow-res models
  and texture images
• Force model inspired by psychophysics studies
• Image-space algorithm for PD computation
  (implemented on GPU)

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Results

• 500Hz force update rate with relatively simple
  models
• 100Hz-200Hz force update rate with complex models
• Haptic rendering of interaction between complex
  textured models

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Limitations

• Cannot handle surfaces that cannot be described
  as height fields in the contact region
• Possible sampling-related aliasing
• Limited stability with high PD gradient

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Future Work

• Higher frequency textures
• Deformable textured surfaces
• Analysis of human factors

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References

• Haptic Display of Interaction between Textured
  Models.Miguel A. Otaduy, Nitin Jain, Avneesh Sud
  and Ming C. Lin.In Proc. of IEEE Visualization
  Conference 2004.
• A Perceptually-Inspired Force Model for Haptic
  Texture Rendering. Miguel A. Otaduy and Ming C.
  Lin.In Proc. of the Symposium on Applied
  Perception in Graphics and Visualization 2004.
• http//gamma.cs.unc.edu/HTextures/