week 12 summary [Hitesh]
Exploring 3D navigation:
Navigating an interacting in a 3D world is a lot more challenging than rendering one. Also, the usability and effectiveness of a virtual environment largely depends upon the user’s ability to get around and interact with the information within it. The paper discusses previous research efforts to construct taxonomy of navigation techniques. The paper refers to previous graphical interfaces which had zooming as the principle mode of interaction but the user had to manually keep track of the different viewpoints. The proposed system intended to provide global view of documents as well as local view to inspect specific targets. The Taxonomy discussed can be broken into three subtasks – exploration ( to gain survey knowledge) ; search( to locate an object to navigate); and inspection( to establish and maintain a particular view of an object).
Four techniques have been discussed –
‘Object manipulation and ghost copy’ is used for Inspection. The user drags on an object and then manipulates a copy of this object, placing it at desired position and orientation. When released, copy is removed and object animates to the exact location that provide the specified orientation and scale to the object.
‘Inverse fog or scaling an ephemeral world’ is used for searching. The user controls the radius of a sphere. Objects within the sphere are either made transparent (inverse fog) or scaled down (ephemeral world).
The two others techniques for moded tasks: ‘Possession and rubbernek’ navigation. User selects an object to move to the exact orientation and position of the object, from first point of view. It can then chose the orientation and create on the fly a new camera. The second technique is the ‘speed coupled flying without orbit’ wherein cursor determines the operation. Dragging on an object implies examining an object. Otherwise, dragging on the floor or wall implies user wants to freely move around the object. Experiments suggest that speed coupling without flying orbit offers the better result.
A Survey of Design Issues in Spatial Input
The paper focuses essentially on the design issues for developing effective 3D user interfaces. Existing 3D input technologies for developing spatial input freespace interfaces, such as camera or magnetic based trackers have their own issues. Previous spatial interaction techniques have mainly revolved around two types – single applications for specialized tasks and formal studies which analyze individual phenomena in isolation. Paper discusses design issues into two major categories, those dealing with human perception, and those dealing with ergonomic concerns. The specific issues within these categories have been discussed in detail in the paper.
Human perception should serve as important guidelines while designing such as considering between Relative and Absolute gesture; two handed interaction are more intuitive for users; Multi-sensory stimuli, like force feedback, space exclusion or auditory feedback and Head tracking, can provide useful information to the user; and considering physical constraints to reduce cognitive load on the user. Specific factors in Ergonomics that should impact design are – providing multiple degrees of freedom in coarse vs precise positioning; dynamic target acquisition; understanding the affordances of multi-modal input; understanding the dynamics and working volume of user’s hand; and efficient clutching mechanisms.
Designing for a 3D spatial interface is lot more challenging than 2D interfaces and requires considering a broad range of usability principles w.r.t human perception and cognition, physical abilities and limitations, multi-modal nature and range of interactions, virtual environment (desktop, HMD etc.) and the purpose of the system. The design principles and evaluation of such interfaces would constantly evolve with progress in the field of Virtual environments.
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