Interactive 4D Overview and Detail Visualization in Augmented Reality

Figure 3: Object time overview visualization: providing information of multiple points in time for a single object. The multiple points in time are
thereby color coded. Left: Heightlines showing the different height of the wall at different points in time. Middle Left: Geometric Completion
shows the completion in geometric reference to the wall. This provides a summary which parts of the wall were added at which time. Middle
Right: Completion diagram showing the average completion for multiple points in time. Right: Block diagram showing the average completion of
the wall for multiple points in time.
tion site. Such a visualization is adequate for distant views such as
birds eye views where multiple objects are visible.
In our work, we use such an per-object-abstraction for overview
visualization on the scene overview level. However, combined with
filtering techniques, we use this visualization layer as a starting
point for further inspection on a per object-basis. As shown in Figure
2 (Top) real scene objects are colored with colors representing
their current status. Additionally, measurements can be displayed
on the object. A limitation of this visualization level is that it can
only represent one single point in time or a single value to summarize
the data in one view.
L1: Object time overview level The visualization of the scene
overview level provides a quick overview over all areas of interest
in the scene, but restricts inspecting a selected area in more detail.
To understand the current status of an object in relation to earlier
points in time and its geometry, we introduce a new level showing
information of multiple steps in reference to the object’s geometry.
To get an overview of the object’s change over time, we visualize
abstract information that summarizes the object’s status for each
point in time. This abstraction already conveys the evolution of the
object’s shape over time using outlines, contours or average diagrams,
while retaining enough abstraction to show the whole time
series. Different visual abstraction techniques enable for effective
information presentation at this level. For example,
• Height Lines: representing the different heights of an area at
different times (compare Figure 3, Left).
• Geometric completion: abstract information with geometric
reference. For instance a diagram showing average completion,
color coded completion (compare Figure 3, Middle Left
and Middle Right).
• Block diagram for average completion: block diagram showing
the average completion in relation the geometry of the
object of interest (compare Figure 3, Right).
L2: Detail Level The last visualization level allows to inspect
the detailed geometry and appearance of an earlier version by rendering
the representation of the earlier version itself. In the overlay
of the 4D data, the user can inspect the progress on the object in
a detailed way. Furthermore, color-coded shading of 3D structure
can be applied to support visual discrimination objects at different
points in time (Figure 4).
3.2 Transitions between Visualization Levels
After introducing the visualization levels, the second challenge is
the interactive transition between them. In this section we discuss
a concept for interaction methods that allow the user to navigate
between the visualization levels. Additionally, details on the implementation
of interaction techniques are then given in Section 4.3. A
user starts in the first level and selects objects of interest for further
Figure 4: Color-coded shadings of a wall geometry at different points
in time.
inspection in the other levels. For example, by filtering the objects
based on their progress in L0, only objects with a certain amount
of progress or completion are shown. Afterwards the user can select
or physically move to an object of a certain amount progress or
completion. We connect all levels by interactive view manipulation
techniques providing visual continuity when drilling down for more
details.
Managing contextual and focused information has a long tradition
in information visualization. In our approach, we use in each
level the real world structure as well as abstract representations as
contextual information next to detailed information, which are currently
in the focus of an analysis. This allows us to apply similar
visualizations for moving between the three abstraction levels in the
visualization space. As described by Cockburn et al. [4], overview
and detail techniques may separate focus and context information
temporally or in space by applying, for instance, zooming techniques
or by presenting the data in separated views. Focus and
context techniques integrate these information in one single view
and present context and focus information together.
3.2.1 Overview and detail
The first level of abstraction is used to present an overview of the
environment. Due to the highly abstract character of this level, less
information is presented and thus it is possible to inspect more objects
at once. In contrast, the second level of abstraction provides
more detail that may easily clutter an overview visualization. The
falloff in detail of the visualization levels makes the transition between
the first and the second level a perfect candidate for overview
and detail techniques. However, providing techniques for switching
between overview and detail visualization is crucial for the acceptance
of any tool for visual analysis. Thus, we provide two common
techniques for transitions between overview and detail visualizations.
A zooming interface and a WIM presentation allows us to
comprehensively transition between the first and the second level
of abstraction.
Zooming The zooming interface allows the user to zoom out
of his current view. Based on the amount of zooming this provides
an overview of the scene where the user can inspect multiple objects
at once. With larger distance to the scene, the interest on detailed
information gets less and more abstract representations of the scene
objects are presented (Figure 5, Left).