Search PubMed⌕ Search

Biomedical subjects

G J Smets

Publications and source records attributed to G J Smets.

7 recordsLinked to original sources
PubMed1997

Cubby. A medical virtual environment based on multiscreen movement parallax.

In this paper a desktop virtual reality system named Cubby is described. Cubby is based on self-induced, head-coupled movement parallax on three orthogonal screens. It is argued that this system is better suited to medical practice than Immersive VR solutions or single screen Desktop VR systems. Whilst Cubby is currently limited to visualisation it opens up possibilities of direct instrumental manipulation and as such could prove useful as a medical simulator.

Computer Simulation↗
PubMed1997

Spatial perception during laparoscopy: implementing action-perception coupling.

Laparoscopy is a telepresence task since the surgeon has no direct contract with the patient. Performance of the surgeon will increase if his sense of telepresence is improved. This can be achieved by restoring the hampered action perception coupling. With respect to visual perception this means that the surgeon should be informed about the spatial lay-out of the environment; depth information and information about the location of observation. Both types of information can be provided by allowing the surgeon to explore. This paper describes our work on restoring the action perception coupling with respect to visual perception. It provides an overview of different technical solutions which balance between what information should be provided from an perceptual stand point and what information can be provided from a technical viewpoint.

Depth Perception↗
PubMed1989

Scent and sound of vision: expressing scent or sound as visual forms.

This article describes three experiments on the possibility of expressing scent or sound into visual forms made by design engineering students. The hypothesis tested was that people are able to pick up patterns in the energy flow that the students transposed from one perceptual sense to another. In Exp. 1 subjects were given different scents and were asked to choose a sculpture designed according these scents. In Exp. 2 subjects were given different musical pieces and asked to match them with portable cassette players designed according to this music. Exp. 3 was identical to Exp. 2 but different music selections, similar to the ones in Exp. 2, were used. In all three experiments subjects were indeed able to perform the tasks above chance level. Results are discussed within the framework of the theory of direct perception of Gibson.

Arousal↗
PubMed1988

Form discrimination: features or invariants?

Does form discrimination rely on feature analysis, as the indirect theory of perception supposes, or on affordances (behavioural meanings specified by invariant patterns), as direct theory states. Subjects were to indicate the position of a target in a perspective rendering of a plane, displayed for 100 msec. in a large screen projection. In one of the conditions the target disrupted the plane, in the other it did not. Although targets of the two conditions shared the same features, the disruptive targets were discriminated more often than the nondisruptive targets. This result supports the direct approach to perception which states that a perceiver discriminates behaviourally relevant patterns rather than geometrical properties.

Adolescent↗
PubMed1987

Depth on a flat screen.

The hypothesis was tested that the coupling of parallax shifts between objects depicted on a monitor screen around a fixation point with the head movements of an observer viewing this screen monocularly around a point coinciding with the fixation point is sufficient to create a convincing depth impression and to enable the observer to make reliable estimations of depth. The estimates were based on monocular vision and involved the aligning of wedges. The investigation consisted of two analogous experiments carried out simultaneously, one on depth estimations virtually in the screen and one on depth estimations virtually in front of the screen. In each experiment three conditions were compared: an active condition in which the coupling of parallax shifts and observer's head movements operated, a passive condition in which it did not, and a real-life set-up to measure the maximum reliability in depth estimation. The hypothesis is confirmed: in the active condition the variances in the alignments are significantly smaller than in the passive condition and approach those in the real-life set-up. This holds not only for estimates in the screen but also for estimates in front of the screen, that is, we can make a thing apparently leap out of the screen towards the observer. Results are interpreted against the background of the debate between the direct and the indirect theories of perception.

Cues↗
PubMedDate not supplied

Using movement parallax for 3D laparoscopy.

The lack of depth perception hampers the surgeon during laparoscopic operation. Laparoscopes usually are monocular, but binocular ones are currently available. Depth perception, however, does not exclusively rely on binocular disparity. An observer, with only one eye, who is able to move that eye, obtains the same information as an observer who has two eyes. This principle of movement parallax can be applied to laparoscopy by coupling the head movements of the surgeon to the motions of the tip of the laparoscope. In an experiment we investigated if this principle is applicable to laparoscopy. Two groups of testees with no background in surgery were used. The first group was assisted by movement parallax, the second group was viewing a static image. Both groups of testees had to perform an exploration and a manipulation task. Since the amount of space for camera motion within the laparoscope is limited, implementation potential depends on the amount of movements that will be made by the observer. Therefore the movements of the observer performing the exploration task were registered and analysed. Results of the experiment indicate the advantage of movement parallax for the exploration task (performance increases by factor 2 while using only 30% more time) but not for the manipulation task. The analysis of the movements indicates that small movements are sufficient for implementation. Based on these results we concluded that movement parallax is applicable to laparoscopy.

Depth Perception↗