Tools

user can still be represented within the graphical medium but they cannot perceive anything in that medium (their graphical embodiment has a “T” on its forehead to indicate this to other graphical users). The text medium is useful in combination with the audio and/or graphical media as it provides a map view of the surroundings, and supports reliable messaging which is resilient to network congestion (unlike real-time audio).

4.2. Tools

The previous section described the facilities which users of MASSIVE-1 have to interact and communicate within a shared virtual world through the graphical, audio

Table 5: effects of awareness level on presentation of the text message “hello” from user “Chris”

Awareness of Chris Text Displayed

less than 0.4 nothing

0.4-0.6 “Chris says something” 0.6-0.8 “(Chris says hello)” 0.8-1.0 “Chris says hello”

4.2.1. Message board

and text media. To supplement this direct communication the system also includes a number of active objects which may be placed within a virtual world to create oppor- tunities for other types of interaction. These active objects are a message board, a text to speech convertor and spatial model adapters. These tools are described in turn.

4.2.1. Message board

The message board is a specialised process which interfaces with both the text and graphical media. It “listens” in the text medium for message which are directed to it. It determines which messages are directed to it by checking the awareness level which the message board has of the message’s sender. This takes into account both the mes- sage board’s focus, which picks out senders that are in front of the board and rela- tively close to it, and the sender’s nimbus, whatever that may be. The message board displays in the graphical medium the last few messages which it has received at high awareness. So users can add text to the board by approaching it (to increase its aware- ness of them) and typing a message in their text client. The board makes these mes- sages available in a more persistent form in the graphical medium. A meeting around a message board is shown in figure 9 on page 40.

4.2.2. Text to speech convertor

The second tool, the text to speech convertor, has many similarities to the message board, above. It monitors the text medium for messages which are directed to it and reproduces them in the audio medium. The text to speech convertor makes use of a

4.2.3. Adapters

freely available (low quality) software speech synthesizer, interfacing it to the text medium for input and repackaging and re-sending its output in the audio medium. The text to speech convertor gives feedback to a user by changing its appearance when it is aware of them (a simple representation of a face is displayed). This appearance is specific to each observer and is an example of “subjectivity” in a virtual environment (see [Snowdon et al., 1995]).

The message board and the text to speech convertor both demonstrate how the spatial model can be used by agents wishing to take an appropriate role in multi-user, multi-agent settings. Using negotiated awareness levels these tools to are able to dis- tinguish between background conversation and directed statements which might be commands or requests. The tool’s awareness of a text message depends on its own focus, i.e. where the sending participant stands in relation to the tool, and the partici- pant’s nimbus, i.e. how they are projecting themselves in the space. Thus a tool can be made to respond only to text messages which are directed to it (participant’s nimbus) and which come from participants standing just in from of the tool (tool’s focus). This theme is explored further in [Benford and Greenhalgh, 1995].

4.2.3. Adapters

MASSIVE-1 supports adapter objects as proposed in [Benford and Fahlén, 1993]. Adapters are objects which change (or replace) a user’s auras, foci and nimbi in order to transform the way in which they interact and communicate. The two adapters which have been used in MASSIVE-1 are a podium and a conference table (c.f. [Fahlén et al., 1993]). When a person stands on the podium they are given large auras and nimbi so that they can be seen and heard at a greater distance; this facilitates lec- turing and similar patterns of communication. When a person approaches the confer- ence table their auras, foci and nimbi are transformed to encompass the table and its immediate surroundings, but to restrict interaction further away; this creates a self-contained mutually aware group when participants gather around the conference table.

Adapters in MASSIVE-1 - like those in the spatial model of interaction - affect indi- vidual objects, changing their auras, foci and nimbi (this may be contrasted with the form of adaptation found with third party objects in chapter 7, which acts directly on the relationships between pairs of objects). Adapters are triggered by proximity which is determined by aura collision in a specialised “adapter medium”. It is simple to cre- ate new adapters in MASSIVE-1 which have different parameters for aura, focus and nimbus. However it is not possible to combine adapters or to move or carry them.

4.2.4. Summary

This section has described a number of tools which enrich communication within vir- tual worlds. The message board enhances interaction between text and graphical users and introduces an element of support for asynchronous interaction (e.g. leaving mes- sages for others to find at a later time). The text to speech adapter further enhances the potential involvement of text users in an otherwise audio-visual world; the addition of speech to text conversion would “complete the loop”. Adapter objects allow different forms of interaction such as lecturing or focused group discussion in particular spaces. This concludes the description of the external characteristics of MASSIVE-1. The next two sections describe the implementation of the system, specifically the dis-