INTERACTION TECHNIQUE / INTERACTION METAPHOR DRIVEN SOLUTIONS

This category of 3D navigation solutions is centered on the interactive protocol of how the user is supposed to complete their navigation task. Typically, these solutions are regarded as possessing an intangible interactive choreography that dictates how the remaining elements of the solution should fit together.

The main difference between ITs and IMs, in the context of 3D navigation, is the association of the navigation protocols to some existing real-world entity in the form of an explicit simile [53]. As previously stated in the IM section for general 3DUI solutions, the best metaphors for describing ITs are those that match the tasks and system and those that are already known or are easily understood to the user. Applying this principle to 3D navigation, an appropriate IM would be a common or simple real-world entity that is either navigational in nature or else could be easily applied to the task of navigation. It should blatantly inform the user about the navigational affordances and constraints that would exist with this solution. For example, connecting 3D navigation to riding a tour- bus should suggest to the user that, while they may be afforded discrete choices of destination locations, their lower-level navigational behaviors may be constrained.

This introduces an interesting aspect to the design of IMs, namely the spectrum of conceptual distance between the act of navigation and the metaphor that is attempting to be applied. Specifically, there is a choice on whether to use what some may consider conceptually similar navigation metaphors – such as linking 3D navigation to driving a car – or whether it may be advantageous to inventively apply or create a conceptually incongruous metaphor – such as linking 3D navigation to the act of drawing with a pencil. Up to this point, many existing 3D navigation solutions have made use of connecting their tasks to real-world navigational strategies, such as vehicular travel [53] and traveling with the aid of a map [47]. It is useful to note cases when metaphors that are not quite navigational in nature, but are very close, are applied to afford navigation. In these cases, the resulting IM becomes a new hybrid entity which is a combination of the

pre-existing definition of the chosen metaphor that is modified to fit the model of 3D navigation. In these cases, the actual metaphor will not exist in reality. For example, our IM of Navigational Puppetry is a hybrid metaphor that allows the real-world entity of puppeteering, which has certain navigational elements but is not exclusively navigational in nature, to be considered in the context of navigation.

We have previously outlined the following issues that should completely inform the design and implementation aspects of the IT / IM elements of an entire 3D navigation solution:

- Must decide between an IT or IM?

o A decision must be made on whether to describe, design, and implement the interactions of the solution as either:

ƒ IT: a set of non-cohesive protocols to describe the solutions affordances and constraints

ƒ IM: an explicit simile between 3D navigation and a real-world entity that cohesively explains the affordances and constraints of the solution, making use of either existing user knowledge of the real-world entity or blatant conceptual connections between the task and metaphor

- Other important factors to consider when considering a metaphor candidate: o How closely related to navigation is it?

o Will it require the creation of a new hybrid definition of itself for the IM?

o How well will it compliment the other solution elements?

Examples

One of the most popular and simplest 3D navigation metaphors is flying. Chuck Blanchard of VPL has been famously quoted making the statement “… nobody walks in

VR (virtual reality) – they all fly …” [21]. While flight is not the most natural human

connection to navigation, it remains quite an easy solution to understand and implement. Many solutions actually get more specific when they use flight as an IM. For example, architectural walkthrough systems have been known to use a joystick and an interaction metaphor that relates to helicopter flight [21]. Ware et al also take the generic flying metaphor in other interesting directions [53]. They have experimented with their IM of a ‘flying vehicle’, which involves the manual manipulation of a miniature flying vehicle model that was considered to be in locomotion (like a child playing with a toy airplane). In the same vein, they also investigated a slightly more abstract take on the flying metaphor called the ‘eyeball in hand’. This version of the IM involves the manual manipulation of a flying eyeball device, which is essentially quite similar to the ‘flying vehicle’ metaphor, except there is less of a focus on vehicular locomotion and more on 1- to-1 movements of the ‘eyeball’ as if it were a camera.

Another interesting non-navigational metaphor that has been experimented with involves the idea of manual viewpoint manipulations. These types of IM are used in 3D navigation solutions that concentrate on the user’s manual gestures (often captured by data gloves or sensors places on the hands) to complete navigation tasks. For example, there have been

studies performed where the user ‘grabs the air’ and pulls themselves forward, as if they are standing on a skateboard and are pulling themselves by some rope that is rigidly attached somewhere off in the distance [4] [5].

It is possible that more realistic metaphors, like map aided car navigation, can produce affordances that result in quite an unnatural navigation experience. For example, an interactive map of VE can be presented to the user and they can ‘teleport’ themselves to any discrete location instantaneously [3] [47]. Alternatively, the user could simply choose discrete locations on the map as milestones of a path or route that they wish to follow.