Interactive 4D Overview and Detail Visualization in Augmented Reality

icg.tugraz.at

Interactive 4D Overview and Detail Visualization in Augmented Reality

Overview

Overview and Detail

Scene overview

Object time overview

Object detail

Detail

Focus and Context

Figure 2: 4D visualization concept. Multiple level of detail allow to explore time-oriented data in an Augmented Reality visualization. The highest

level of abstraction provides just enough information to provide an overview of the data in relation to the objects in the AR environment. The

second level of abstraction presents traditional time-oriented visualizations registered in AR to enable an effective analysis of time-oriented data.

Its registration in AR additionally provides information about its relation to real world structure. The third level provides structural detail of the

object of interest for a selected point in time and 3D space. To allow to first study the data in a higher level of abstraction before analyzing it in

more detail we interactively combine all level using overview + detail and focus + context techniques.

ceptual issues such as change blindness. Therefore, it is not enough

to use a time slider to browse through complex data sets, which include

a high number of changes in-between the different instances

(see Figure 1, Left and Middle). In addition, even when focusing

on a few variations between multiple versions, it is mentally more

challenging to keep track of them over time.

In consequence, we analyze time-oriented data within a single

view. However, simply blending 3D structure of multiple points in

time into the same 3D space may heavily suffer from occlusions and

clutter (Figure 1, Right). A simple blending results in visualizations

that are not comprehensible. Furthermore, using such an overlay

occludes a large part of the contextual information.

To support effective ways of studying the development of 3D

structure over multiple points in time, we have to simplify the visualization.

Therefore, we abstract the presentation of individual

parts both in space and time. The general idea of the interactive 4D

overview and detail visualization is to provide three visualization

levels varying in their level of detail. To clarify the description of

these visualization levels, we group the virtual content presented in

the visualization in the following way: (1) The Scene describes all

virtual objects of interest in the visualization. In Figure 2 the scene

is the set of walls of the white building. (2) The Object describes

one object of interest in general. For instance, in Figure 2 an object

is one of the walls of the white building. The object itself can be

represented by rendering an abstract visualization of a certain characteristic

of this object, an overview of multiple points in time or

by rendering the object in detail for a selected point in time. (3)

The Object Detail refers to the actual geometry and appearance of

one object at a selected point in time (Figure 2 Bottom). The visualization

levels are based on this content grouping and display

the virtual content on different scales. They show information on a

scene overview scale, on an object time overview scale and on an

object detail scale:

• L0: Scene overview level

• L1: Object time overview level

• L2: Object detail level

The first visualization level L0 represents abstract information

for individual objects through aggregating time-oriented attributes

per object. These attributes may include information such as completion

or progress and will be represented with a per-object visualization

such as a color coding. While the first level allows for

global filtering of information, the second level L1 presents information

about the variation in time of an attribute, in relation to the

object’s geometry. For example, the evolution of an object’s degree

of completion can be analyzed in more detail through color coding

parts of the 3D object, contour diagrams or simple charts which are

registered in 3D space. The third visualization level L2 uses the

highest degree of detail by presenting a complete 3D rendering of

the objects at a different points in time. By augmenting the scene

with geometry from previous points in time, the user is able to travel

through time and inspect 3D structure in detail, even in relation to

the real world environment of his current point in time. His travel

depends on his prior analysis of a higher level of abstraction, which

allows for more effective comparison of multiple points in time in

single view than detailed renderings of complex 3D structures.

Each visualization level is a detailed view of the higher visualization

level. Transition techniques such as overview & detail and

focus & context allow to move between the different visualization

level and to relate them to each other. We first discuss each level of

abstraction in detail before we describe how we move from one to

the other.

3.1 4D Visualization Level

In the following we describe the levels in detail.

L0: Scene overview level Since 4D data is usually rather

complex, it is hard to explore and visualize such data. Particularly,

in on-site scenarios, users should find interesting objects quickly

despite being limited to a small screen size. Therefore it is important

that a visualization technique provides a good overview of

the scene and guides the user to conspicuous objects. Abstract visualization

that show summary information without any detail can

support user in finding these objects.

Golparvar-Fard et al. [8] used color coding on a per object-basis

to visualize different measurements for a complete construction site

such as completion and progress, criticality or cost in a Mixed Reality

visualization. In their work they show registered color coded

BIM models over a previous captured camera image of a construc-

More magazines by this user
Similar magazines