ÍNDICE DE FIGURAS ACRÓNIMOS
1. PRINCIPIOS, ÁMBITO DE APLICACIÓN Y OBJETIVOS 1 PRINCIPIOS
Stemming from the fact that human visual processing is an evolved system is the manner in which change within an environment is detected. In order to understand why it might be that humans are poor at determining certain types of change in surroundings, it requires that the manner in which visual data is processed is understood.
It is a feature of the way that the human eye perceives colour and light intensity via two independent types of cell that the intensity of light particularly in the peripheral vision is predominant to any colour information that is registered largely in the fovea centralis. The colour detecting cones also require significantly greater stimulus in order to deliver a signal to the brain. It has been demonstrated that humans cannot detect even abrupt isoluminant colour changes in parallel, whereas small luminance changes are readily detected (Theeuwes, 1995), colour changes may be detected at the periphery of vision, but only if accompanied by a luminance change.
Human working memory (Baddeley & Hitch, 1974) is not restricted to matters of short-term memory; it is concerned with dealing with attention given to tasks that require monitoring. The manner in which the details of a scene are stored is understood to be coded in the visuospatial sketchpad Figure 103 and related semantically to long-term memories for instance to previously defined or remembered objects (Baddeley & Hitch, 1974). It is due to the way in which the brain creates shorthand associations for inputs that, although the broad sense of what is being perceived is coherent, the granularity or finer detail is lost.
Figure 103. Baddeley and Hitch's working memory diagram (TiCS)
From a neurological perspective, the fact that these interweaving systems appear to operate in a semi-autonomous manner can be related to the method by which storage and processing of different types of sensory data are handled independently within the structure of the brain (Baddeley, Logie, Bressi, Sala, & Spinnler, 1986). Figure 104.
Change blindness (Pashler, 1988) is a phenomenon that appears to relate directly to the manner in which visual data is captured, processed and stored by the brain. A range of types of change blindness have been shown to exist, the most extensively researched are saccadic change blindness (Grimes, 1996) where the eye moves abruptly from one object to another, skipping over entire aspects of a scene that are not the main focus (Simons & Chabris, 1999). The flicker paradigm introduces change between two images but inserts a blank image between the two main images (Pashler, 1988). A clear demonstration of inattentional blindness and its relation to working memory is presented in the basketball counting exercise (Simons & Chabris, 1999) in which two teams of basketball players pass balls to each other. While the viewer is counting the passes the white team makes, a man dressed as a gorilla walks into the centre of shot beats his chest and walks off. Despite this being completely obvious to anyone watching and not counting, the majority of first-time participants fail to spot the gorilla. The inattentional blindness demonstrated in this study has implications that relate to the changes that frequently occur within virtual environments and specifically video games; in which –often to reduce the memory overhead- both textural and geometric changes are slowly made, often without the player being attentive to those alterations. Specific examples of this would be the common removal of decal information such as bullet holes or footprints or the slow fading of enemies that have been dispatched by the player. Although virtual environments are commonplace and many of these attempt to engage the participants’ senses by directing attention, there has been little research into the perception of changes in those environments.
2.7.1 REDIRECTED WALKING
A technique which is akin to change blindness in so much that the entire environment is imperceptibly adjusted to create an effect termed: ‘redirected walking’ (Razzaque, Kohn, & Whitton, 2001; Steinicke, Bruder, Ropinski, & Hinrichs, 2008). The user is able to walk continually in a finite space by the gradual adjustment of display angle at an imperceptible rate within a VR system, the user experience the visual environment as zig zag path while due to the rotation of the visual stimulus, they are in fact simply following the same slightly curved path repeatedly. Figure 105.
Figure 105. An overhead representation of the paths taken in [top] the virtual tracked space and [bottom] the laboratory real-world space (Razzaque et al,2008).
Suma et al. (2010) demonstrated that virtual environments could be made to feel much larger than they actually were by triggering manipulations of the geometry within the scene, essentially having the participants enter, leave and re-enter the same room repeatedly while thinking they were entering new spaces. This involved the player entering a room containing a desk. When the player interacts with the computer on the desk, the doorway the player entered moves from its original position to the wall 90 degrees to its original location. When the player turns around to exit the room, the change in alignment is not registered, and these rotations could be continued cyclically indefinitely, the participant therefore experiencing a very long corridor containing many adjacent spaces where in reality, they are simply walking around in a continuous square pattern in the same finite space. This effect has been implemented by designers of the mixed reality experience The Void (Metz, 2015) which superimposes a virtual world on top of a prebuilt physical environment, demonstrating that in practice, the effect translates from experimental scenario to real world application. In this instance, the use of redirected walking is able to separate two players by having them enter different spaces while their perception is that of walking in a linear fashion accompanied by the other participant.
Beyond these examples, change blindness in virtual environments is a broadly overlooked area
for study. This is despite its casual use in a vast range of titles to remove by slow fade, memory intensive elements such as bullet hole decals on walls, footprints in the snow or even in
some cases the bodies of defeated enemies can fade from view and unless directly watched this wholesale removal of geometry remains undetected. An aspect of this removal of player created change in the environment is that, where the player may have been able to utilise those inclusions as an analogue of a breadcrumbs trail, and therefore retrace a prior path, such navigational cues are lost once the system removes them from the environment.