Introduction to Computer Haptics Chris Harding chardingiastate edu

Introduction to Computer Haptics Chris Harding charding@iastate. edu

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 2 D/3 D visual stimuli to the user Haptic Rendering: process of displaying synthetically generated 2 D/3 D haptic stimuli to the user Motors, cables, actuators, position sensors, … F End-effector (pen, thimble, surgical instrument, …) simulated haptic probe Haptic Interface: device for touch interactions in real and virtual worlds

Human vs Machine Haptics:

Machine Haptics: Types of Haptic Devices Force feedback Displays (Kinesthetic: position) Tactile Displays (skin)

Types of Haptic Devices Passive Active Force keyboard, trackball, mice, etc.

Types of Haptic Devices Grounded Attached combined Hulk strong – crush Coke can !!

Applications Haptic Feedback for Molecular Simulation Haptic Feedback for Medical Simulation and Training force molecule Haptic Display Visual Display

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 Haptic User Interface (HUI) Simulation of repair and maintenance tasks Haptic Feedback for Crew Training

• Geometry • Color • Stiffness • Deformability

Point-based Haptic feedback n Problem: q q n 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 PHANt. OM): q q q Use only a single point (3 DOF): point with stylus (direction vector) GHOST API, Reach. In API, Open. HL

Virtual Finger Tip Stylus Tip

Haptic Rendering with a Force Display virtual wall Position Orientation Collision Detection Object Database Geometry Contact Information Material F= stiffness * dist Force Collision Response

point-object interaction HIP = Haptic Interface Point: True (real world) position of stylus tip Hand: always drawn outside the sphere Assumption: Stiffness = 1. 0

Haptic Rendering of 3 D Objects via Proxy (point-object interaction) d: Proxy to Tip distance HIP (stylus tip: actual position!) F=k*d (Hooke’s Law) Spring with stiffness k Proxy (displayed position) (If in doubt: the visual sense will override the sense of touch …)

Haptic Rendering of Polygonal Surfaces HIP = actual tip position IHIP = Proxy point

Haptic Display of Surface Details n n n Haptic smoothing of object surfacesding)(similar to Phong shag Rendering of haptic textures Haptic rendering of surfaces with friction ( displayed shape actual shape

Haptic Texturing • image-based s two-stage mapping Bier & Sloan, 1986 t • procedural bump mapping h(x, y, z) Blinn, 1978; Max and Becker, 1994

Force-Reflecting Deformable Models: Surgical Simulation F F Haptic Sculpting/painting

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

Sensable Omni Phantom n n n New, “cheap” version of phantom line Stiffness: 3 - 4 N Firewire port Windows, Linux (? ) Open. HL API: (low-level Open. GL-like haptics) Demo of virtual clay sculpting (splodge? )

Conclusion n n 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: q q Surgical simulation and training assembly/repair planning Virtual clay sculpting (art, rapid prototyping) Sculpting of subsurface layers (saltdome modelling)