Haptic Applications to Virtual worlds:

1) Introduction

With the advent of virtual technology it is evident that the world ofcomputers is attempting to imitate the real world. In the real worldpeople receive and disseminate information in three dimensional space. Incommunicative modes such as conversation, the relative position andgestures in three dimensional space carry large amounts of information. In educational spaces such as museums different topics and levels ofdetail are separated by space. In stores shoppers perceive categories overspace.

While graphical user interfaces allow computer users to accessinformation using iconography, a virtual world allows a user to accessinformation by imitating the three dimensional space that exists in thereal world. We refer to this imitation of real space as virtual space. Inthe real world our primary interface with the physical is our haptic sense(sense of touch). So, in order to complete the imitation of real space onewould expect that a haptic interface would be necessary. A hapticinterface is a device which allows a user to interact with a computer byreceiving tactile feed back. A haptic device achieves this feedback byapplying a degree of opposing force to the user along the x, y, and z axes.

A haptic interface serves to orient users to the location and nature ofobjects in a virtual space. An orthotic interface, whether embracing theentire upper body or only the tip of a finger, gives the user informationabout the nature of objects inside the world. A less complicated interfacewhich conveyed haptic information through a device akin to a pointershows the user a tactile map of the area. The focus of this paper will beon the former of these two devices, and its potential for operating invirtual space created with the virtual reality modelling language.

The virtual reality modelling language (VRML) has been designed to createdynamic virtual spaces in an extremely efficient formate to facilitate thesending of these virtual spaces over the internet. As yet a user of avirtual space created with VRML is limited to visual and aural interaction. Section four of this paper will discuss ways in which a virtual spacecreated with VRML could send relevant data to a haptic interface.

There are many access issues surrounding the implementation of a hapticinterface. The haptic sense can be used to give information in the place ofvision or hearing. Aspects of a virtual space which require hapticmanipulation could eventually provide barriers to users with mobilityimpairments. These issues will be discussed in section three.

The haptic sense is unique in that, unlike the passive senses of vision andhearing, action (manipulation) always precedes perception. This meansthat in order for a haptic interface to be effective certain considerationsneed to be taken in the creation of virtual space.

2) Haptic considerations in the creation of virtual space.

The creation and exploration of virtual spaces will always be a creativeeffort guided by the purpose of the space. The following points areintended as guides to creating virtual spaces with a mind to users ofhaptic interfaces, not as absolutes to which every virtual space should orwill conform.

The nature of the haptic sense means that perceived objects must bewithin manipulating range. This means the position of objects relevant tothe haptic sense is important. Objects should be placed withinmanipulating range of a viewpoint (0.5 meters). This allows a users toquickly scan or sweep the area and perceive all relevant haptic datawithout relying on a visual display. It also accommodates easy perceptionof haptic data without requiring the user to change position.

Preset positions to which a user can jump are very important to the userof a haptic interface. As stated in the previous paragraph such a presetposition will take the user within haptic range of the object(s) to beperceived. Preset positions will also be a great assist in navigationallowing a user to move from point to point without moving through a voidwhich contains no haptic data to be guided by. In real space we are inconstant contact with the physical world around us. A haptic interface iscapable of imitating this contact if the designer makes appropriateconsiderations.

In the real world people perceive separation of topics, categories, andlevel of detail over space. It is most intuitive for the user of a hapticinterface to be able to perceive these separations in the space they areexploring. For instance in a space designed to disseminate travelinformation for Australia an object in front of the user may be telling theuser about tourist sites in Sydney. An object on the users left may begiving current weather conditions, while on the right a suggested packinglist is displayed. For information on Tazmania the user may have to jumpto a new preset position.

A space designed to optimize use for the user of a haptic interface willhave some very specific and unique characteristics. The implementationof a haptic interface also effects the way a user navigates a virtual space.

3) User Access to Virtual Worlds with Haptic Interfaces

With the advent of alternative human computer interfaces such as voicerecognition, and haptic interfaces computer users have the option of usingthe interface which is best suited to their physical and cognitive needsand preferences. As individualised interfaces become more and morecommon designers will have to start designing for the user instead of thekeyboard and mouse.

A computer user with a sensory impairment could use a haptic interfaceto receive information otherwise only available to the impaired sense. Auser with vision impairment could perceive shape, and a user with ahearing impairment could perceive the vibrations caused by sound throughthe haptic interface.

One universal advantage to a haptic interface is the enhancement oftelepresence. When communicating humans send much information throughgesture. A haptic interface would allow a user communicating in a virtualenvironment to make gestures via his or her avatar*. VRML does notpresently support multi user environments but eventually conversing onthe three dimensional web will be a regular component of interacting onthe web.

Users who lack fine motor coordination may find that inputtinginformation with a haptic device easier. Large targets and control areaswould benefit such a user.

Some users who have a mobility impairment may find some tasks difficultor impossible to achieve with a haptic interface. Therefore, it isdesirable to have keyboard equivalents for haptic dependant tasks such aspushing or otherwise manipulating objects.

4) Facilitating haptic interfaces to virtual reality modeling language

There are several ways in which data from a world created with VRMLcould be sent to a haptic device. The main differences between thesemethods are the amount of haptic control the creator has, and the amountthat the VRML language must be modified in order to implement the hapticinterface.

The first possible way to implement a haptic interface would be thecreation of a haptic node in the VRML language. This node would containinformation telling the interface how much relative force the hapticinterface should return when an object is touched. The default value forthis node would be an equal and opposite force to the force applied by theuser. This setting would give the feedback of a solid object withoutmailability. To add mailability the user would specify an opposing force,relative to the user that was less than equal to the force being applied bythe user. To create a rubbery texture the opposing force would be lessthan equal, increasing over distance until the force was equal and oppositeto the users force. This method of adding a haptic interface would requirea significant change to the language, but would give the designer maximumcontrol over haptic output.

A haptic interface could also piggy back on the solids properties. Thesolid properties must be defined in future versions of VRML to facilitatethe implementation of advanced behaviours (ie the rubberyness of a balldefining how it will bounce). A haptic interface could use theseproperties to define the tactile characteristics of an object. While thisoption requires a change to the language the change will also facilitateanother addition to the language. This implementation will allow limitedcontrol of haptic characteristics.

Thirdly, a haptic property could be added to the language which wouldattach tactile data to a node of an object. This would involve a smalladdition to the language and give a designer limited control over thehaptic characteristic of an object.

Lastly, an algorithm could be developed to take the visual characteristicsof an object and translate them into haptic feed back. This method wouldrequire no change in the language, but would not give the designer of avirtual world any control over haptic feed back.

5) Conclusion

A haptic interface would allow the user of a virtual space to perceivephysical characteristics of the space and interact with thosecharacteristics. The ability to interact with the physical characteristicsof a virtual space enhances the illusion of real space.

The unique nature of the haptic sense, and by extension a haptic interface,means that some extensive design considerations must be taken tooptimize a space for a haptic interface.

The implementation of a haptic interface allows a user inside a virtualspace to receive tactile information, allowing for the supplement orreplacement of another possibly damaged sense. Users with fine motorcontrol may also find it easier to use a haptic interface to navigate avirtual space in place of the traditional keyboard and mouse.

The virtual reality modeling language is a means to transmit dynamicvirtual space over the internet. This makes communicating over greatdistances in three dimensional space possible. In order to naturallyconvey the gesture which carries large amounts of information in typicalconversation can only be accomplished with the implementation of ahaptic interface.

There are several ways to implement a haptic interface to a virtual spacecreated with the virtual reality modeling language. These methods vary inthe amount of control that is given to the designer over hapticcharacteristics, and the degree to which the language will have to bechanged in order to accommodate the interface. The access and VRMLcommunities will have to decide which method is best for the successfulcreation of virtual space conducive to navigation and manipulation with ahaptic interface.

By Lake Porter and Jutta Treviranus

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