Workshop I
Perception-based haptic rendering

Duration: Half-day

Organizer
Matthias Harders, Computer Vision Laboratory, ETH Zurich.
Anatole Lécuyer, IRISA, Rennes.
Marc Ernst, Max Planck Institute, Tübingen.


Contact:
Dr. Matthias Harders
Computer Vision Laboratory
ETH Zurich, Sternwartstrasse 7
CH-8092 Zurich, Switzerland
E-mail: mharders@vision.ee.ethz.ch
Tel.: + 41 1 632 52 79
Fax: + 41 1 632 11 99

Lecturers
Marc Ernst, Max Planck Institute
Matthias Harders, ETH Zurich
Vincent Hayward, McGill University
Anatole Lecuyer, INRIA
Gunter Niemeyer, Stanford University
Alan Wing, University of Birmingham
Hong Z.Tan, Purdue University

Summary
Although haptic interaction with objects in our environment plays a fundamental role for human perception, the sense of touch has been far less intensively investigated than other senses in the context of virtual enviroments. For instance, the design of haptic interfaces is more often driven by the availability of technology than by the necessity to solve real users' perceptual issues. There is a need today for a clear change of perspective, and it is time to search how to design haptic enviroments that match properly the human haptic perception. Haptic hardware could be restricted to stimulate the part of the haptic channel which provides the best contribution to the final percept. Furthermore, we could take advantage of interesting properties of human perception such as haptic illusions, cross-modal transfer, synesthesia, etc. In addition, having a deeper understanding of the characteristics of the human haptic system, as well as of the human perceptual processes would help us to develop more effective guidelines for developing and evaluating haptic devices and applications.

The workshop aims at providing answers to the following questions:

• How to design haptic interfaces that are in line with the characteristics of the human perception?
• How to use properties of the human perception to simplify the different components of haptic displays?
• How to take advantage of perceptual phenomena such as haptic illusions and cross-modal influences?
• How to design haptic rendering frameworks, which match human perceptional thresholds?

Summary

This workshop will provide the audience with recent physiological and psychological findings in the field of haptic and multimodal perception and rendering. It will give methodological guidelines for the design of haptic solutions that match the characteristics of the human haptic sense. We will illustrate our approach with successful applications and system, that benefited from information stemming from human perception.

Talks

Alan Wing
Title: Neurophysiology and neuropsychology of active touch.
Abstract:
Active touch is based on a combination of cues from peripheral receptors including skin and muscle. Primary and secondary areas in sensory cortex integrate these. I will review the neurophysiological bases of touch including imaging studies and describe neuropsychological studies of the effects of brain damage on perception.

Marc O. Ernst
Title: Interaction Within Touch: Combining Tactile And Kinesthetic Information
Abstract:
When actively exploring an object with the hand the resulting percept is based on tactile as well as kinesthetic information. The purpose of a series of psychophysical studies that we recently conducted was to investigate the interaction between kinesthetic and tactile information. In a first experiment we investigated the interaction between different cues to haptic shape. We found that position and force signals are both used by the haptic system to determine the final shape percept. Furthermore, we found that the individual reliability of the two signals determines the relative contribution to the shape percept, indicating an optimal integration strategy. In a second experiment we investigated the tactile sensitivity for orientation discrimination during active and passive exploration and found that discrimination thresholds significantly increased during active touch. This indicates some sort of tactile suppression during active touch. In a third experiment we investigated the contribution of different tactile sensations (produced by shear force, slip force, and normal force) to the feeling of "natural" haptic shape. Within a certain range that we could determine quantitatively using psychophysical methods all three cues provide useful information to haptic shape and contribute to a more natural haptic feeling. In conclusion these three experiments demonstrate the tight coupling between kinesthetic and tactile perception which is dependent on whether objects are explored actively or passively.

Hong Z. Tan
Title: Assessing Perceived Quality of Virtual Haptic Surfaces and Textures
Abstract:
Two studies will be presented that illustrate a human-based approach to studying haptic rendering of virtual surfaces. We propose a new concept called perceived instability that captures non-realistic sensations associated with virtual textured surfaces. We then formulate a force-constancy hypothesis that predicts the illusion of surface-height reversal when virtual surfaces vary in both topography and stiffness.

Anatole Lecuyer
Title: Pseudo-Haptic Feedback
Abstract:
This presentation will review the main results obtained in the field of "pseudo-haptic feedback". Pseudo-haptic feedback is a technique meant to simulate haptic sensations in virtual environments without using haptic devices, but using properties of the human visuo-haptic perception. Pseudo-haptic feedback uses visual feedback to distort the haptic perception and generate "haptic illusions". Up to now, pseudo-haptic feedback has been used to simulate several haptic properties such as: friction, stiffness or textures. It has also been implemented in several VR applications such as for vocational training, or medical simulation.

Vincent Hayward
Title: How to use properties of the human perception to simplify the different components of haptic displays?
Abstract:
In the past two years, the McGill University Haptics Lab has been working on several new devices: a handheld vibrotactile device, a contact location display, a planar direct-drive force-feedback device, and a high-density distributed tactile display; named "MicroTactus", "Morpheotron", "Pantograph", and "StreSS", respectively, each targeted at specific approaches to mediate haptic interaction. In this presentation, I will discuss recent enhancements for each of these devices, what drives performance and what provides effectiveness in each case.

Gunter Niemeyer
Title: Event-Based Haptics
Abstract:
Haptic sytems aim to allow users to touch virtual objects. A large part of our normal sense of touch are vibrations and high-frequency transitients we detect at our finger tips. These inform us about material properties, surface features, and/or relative motion, stick/slip, and more. But today's sytems do not render this information, instead only show low frequency and quasi-static forces. They make the virtual world feel soft and spongy, with all surfaces appearing identical. This limitation can be traced to the simple rendering algorithms that are inherited from decades of robotics. Understanding the human's perception requirements, we have developed the concept of Event-Based Haptics. It takes full advantage of typical DC motors to dislpay high frequency transient forces when an event occurs, such as impact or motion across small surface features. These transients are pre-computed or pre-recorded from real events, adjusted as necessary, and presented without feedback from the user. Their short duration up to 50 or 100ms ensures all information is transfered before the user can react, avoiding the need for feedback. Results have shown that users of Event-Based Haptics were unable to distinguish a virtual from an equivalent real surface.

Matthias Harders
Title: Assessing the Fidelity of Haptically Rendered Deformable Objects
Abstract:
A still open question in the area of surgical simulation is the necessary degree of realism. It has to be noted, that the final goal is not to achieve the highest realism possible, but to provide sufficient realism to enable efficient training of a specific surgical skill. An important element in this respect is the haptics module of a simulator. Several components are necessary to generate haptic feedback, including tissue deformation models, tissue material parameters, collision detection algorithms, coupling to the haptic display, and the haptic device. As a first approach to assessing the influence of these different elements on the fidelity of haptic rendering, we carried out a simplified comparison study, which included real linear elastic silicone samples as well as virtually generated counterparts. In this presentation an overview of this work will be provided.

Expected audience
This workshop is open to a heterogeneous audience:

• Interested researchers in the field of applied perception
• Designers of haptic devices and haptic software solutions
• Builders of haptic rendering environments
• End-users of haptic devices

Level of expertise
No specific pre-knowledge or high level of expertise is required.