[week 12 summaries]
Exploring 3D Navigation: Combining Speed-coupled Flying with Orbiting
This paper mainly contains two parts: taxonomy of navigation techniques for 3D virtual environments and a detailed discussion on Speed-coupled Flying with Orbiting technique.
The taxonomy is developed for better exploration and design. Firstly, based on the task category, ie the user’s goal to conduct 3D navigation, the navigation techniques can be divided into applications for explore, search or inspect. In order to successfully meet the user’s goal, the travel controls need to be taken into consideration. Specifically, they are path control, speed control and view point control. Additionally, user interface is of the same importance since it affects user experiences greatly. In the Taxonomy, a detailed category is listed for the designer’s reference
After a short overview of techniques used in 3D navigation, the Speed-coupled Flying with orbit is brought up with detailed description and discussion on the evaluation experiments. To help user easily and intuitively switch between walking around, getting an overview and examining objects, Speed-coupled Flying is utilized. With standard egocentric driving controls, if the user drags the sensor to a particular direction, the further he drags, the faster the camera moves. Meanwhile, the speed is coupled to the camera’s viewing height and angle, such that the user can obtain a global view from top-down for better inspect and search.
Two experiments are conducted to evaluate this technique. Subjects are asked to find cubes in the scene and put them in the correct correspondent drop-pads. Five navigation techniques are evaluated in these experiments. They are basic driving navigation (with and without Orbiting) , Speed-coupled Flying (with and without Orbiting) and Ephmeral World Compression. The difference between these two experiments is that the second one’s Flying with Orbit condition adds a ‘gliding’ behavior to alleviate user’s uncertainty of landing position after flying. The behavior of each technique is measured in overall task time, cube search time, cube carry time, cube carry distance, actual cube carry distance, the number of cubes retrieved and replaced before deadline and user satisfaction. The overall trial time and percent correct indicate Flying with Orbit is better as of shorter time and higher percent correct. And users are satisfied and prefer the Flying with Orbit technique. Plus, it was found out that trails that are conducted with big display tend to have shorter overall trial times.
In all, the taxonomy summarized in this paper serves as a start point and can be refined and extended as further explorations are done. And the experiments reveal Speed-coupled flying combined with Orbiting is a promising technique to help user navigate and inspect.
A Survey of Design Issues in Spatial Input
A framework that collects several scattered issues in developing effective free-space 3D user interfaces is presented with description, analysis and examples.
These issues are categorized into two parts: human perception and ergonomic concerns.
In human perception realm, designer first need to make users understand 3D space. Six spatial interfaces are summarized as to facilitate 3D space perception. They are spatial references, relative gesture vs. absolute gesture, two-handed interaction, multisensory feedback, physical constraints and head tracking techniques. Spatial references suggests that utilizing objects in real space as spatial reference is good for 3D space perception. Relative gesture is better compared to absolute gesture as it requires less concentration to manipulate objects. Two-handed interaction not only improves efficiency, it also makes spatial input comprehensible without additional cognitive load. Multisensory is important since it can collect a variety of feedback to facilitate better interaction. Physical constraints and accordances are other aspects need to be taken into consideration since in some case they are better than simply software constraints. And some studies shows head tracking can improve the sense of immersing.
Besides the 3D space perception, when design the interface, different input devices need to be used with regard to the task’s structure of the perceptual space. Also the control metaphor selection is also important for easily and intuitively operation.
When the user needs to select an object in the 3D space, issues related to searching, targeting is emerging. Usage of transparency like occlusion cues and context can help to search in dynamic. Other techniques like direct positioning, ray casting and cone casting are targeting problems with object selection.
In 3D space, recalibration is another problem. Strategies like command-based strategy, ratcheting strategy and continuous strategy are all good candidate based on the different specific scenarios.
In ergonomics and facility of interaction realm, design and implement issues comes from the mapping of relative gestures. User may have difficulty to conduct precisely control and biomechanical constraints the DoF of translate, rotate and scale. So appropriate mapping from input devices to tasks is of difficulty. It is a challenge to find and characterize a suitable mapping. The design of working volume of user’s hands is also an important aspect to affect user’s experience. They are small and move over time. When we need to extend input devices, instead of using traditional mice and keyboards, alternatives like voice input, touchscreen may appear to be a better choice for a hybrid 2D and 3D interface. Clutching mechanism, if not carefully designed, may result confounding and hard-to-fix usability problems. If the task requires minimum arbitrary rotation, it is good to mount the clutch button directly on the input device. In other cases, if the interface has an alternative, the clutch button can be eliminated. At last but not least, the utilize of ergonomic should not impede user’s move or introduce inconvenience and pains.
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