Interactive rendering techniques were developed for focus+context visualization of 3D indoor models: (1) Semantic cutaways, levels of detail, ghosting, highlighting, and exploded views focus on selected regions while preserving global context. (2) The techniques were implemented using IFC building information models and tested on models ranging from under 100 to over 1,500 elements. (3) Potential applications include facility management and disaster response visualization, and performance depends mainly on model complexity and size.

1. Interactive Rendering Techniques
for Focus+Context Visualization
of virtual 3D Indoor Models
Graduant: Alessandro Florio - 161704
Supervisor: Nicola Conci
Assistant supervisors: Jürgen Döllner, Matthias Trapp
Co-examiner: Niculae Sebe
Trento,
14. October 2014

2. Focus+Context visualization
A. Florio Interactive Rendering Techniques for Focus+Context Visualization of virtual 3D Indoor Models 2
Basic idea:
 Show selected regions in greater detail (focus)
 Preserve global view at reduced detail (context)
 No occlusion (all information is visible simultaneously)
T. Alan Keahey. Network Visualization Course. Indiana University. 2003
The main problem of information visualization is the insufficient space,
which restricts the user in showing detail and context contemporaneously.
The Focus+Context system allows the user to show detailed information
linked with the context, by also having the possibility to focus on other
information by interacting with the system.
Dürsteler, Juan C. "Focus+Context." The digital magazine of InfoVis.net (2002)

3. Motivation
A. Florio Interactive Rendering Techniques for Focus+Context Visualization of virtual 3D Indoor Models 3
 Constructions* are nowadays
designed with CAD programs:
detailed indoor models are
available
 In most applications only the
external shape is used (e.g.,
buildings: used in city models)
Usage of BIMs through a building’s life cycle
http://www.climatetechwiki.org/sites/climatetechwiki.org/files/images/teaser/
building_life_cycle_teaser_image.jpg
*: not only buildings are considered
 Indoor models could be exploited
in many phases of the
construction’s life cycle, but:
 Too much information complicates
understanding
 Occlusion of elements of interest
Indoor models are already available in Google Maps

4. The IFC data model
A. Florio Interactive Rendering Techniques for Focus+Context Visualization of virtual 3D Indoor Models 4
 Open, international
standardized
specification for BIM*
data exchanged
between participants in
buildings’ lifecycle
 Entities with semantics
in an object-based
hierarchy
* Building Information Model
IFC: Industry Foundation Classes
Graphical
representation of
the structure of
different elements
in an IFC dataset

5. Overview
A. Florio Interactive Rendering Techniques for Focus+Context Visualization of virtual 3D Indoor Models 5
 Five rendering techniques for interactive Focus+Context
visualization of IFC models:
 Using two libraries for 3D scene management and GUI:
a) b) c)
d)
e)
a) Semantic-based cut-away views
b) LODs
c) Semantic-based ghosted views
d) Exploded views
e) Highlighting of single objects

6. F+C Rendering Techniques
A. Florio Interactive Rendering Techniques for Focus+Context Visualization of virtual 3D Indoor Models 6
Semantic-based cut-away views
 IFC objects as
osg::Switch
nodes in the
scene graph
 All elements
of the
selected type
are switched
off/on
Example of semantic-based cut-away views

7. F+C Rendering Techniques
A. Florio Interactive Rendering Techniques for Focus+Context Visualization of virtual 3D Indoor Models 7
Levels of Detail (LODs)
 Predefined configurations of cut-away views
Exemplary LOD
Hagedorn, Benjamin, et al.
"Towards an indoor level-of-detail
model for route visualization.„
Mobile Data Management: Systems,
Services and Middleware, 2009.
MDM'09. Tenth International
Conference on. IEEE, 2009.

8. F+C Rendering Techniques
A. Florio Interactive Rendering Techniques for Focus+Context Visualization of virtual 3D Indoor Models 8
Semantic-based ghosted views
 Intermediate
representation
between
switching on
and off
 2 techniques:
transparency,
wireframing
(type-based)
Example of semantic-based ghosted views

9. F+C Rendering Techniques
A. Florio Interactive Rendering Techniques for Focus+Context Visualization of virtual 3D Indoor Models 9
Highlighting of single elements
 All elements rendered
with ghosted view
 Selected element
rendered opaque
 Multiple selection possible
Example of how a single element is highlighted

10. F+C Rendering Techniques
A. Florio Interactive Rendering Techniques for Focus+Context Visualization of virtual 3D Indoor Models 10
Exploded views
 The transformation matrices of storey nodes are updated
with new translation factors depending on floor’s height
Normal building representation Building rendered using exploded views

11. F+C Rendering Techniques
A. Florio Interactive Rendering Techniques for Focus+Context Visualization of virtual 3D Indoor Models 11
Exploded views (automatic)
∀ frame {
if (autoEVenabled) {
bool overlap = checkBBs();
if (overlap) {
while (overlap) {
zOffset += DELTA;
overlap = checkBBs();
}
}
else {
while (!overlap) {
zOffset -= DELTA;
overlap = checkBBs();
}
}
}
}
Explanation of how automatic exploded views work

12. F+C Rendering Techniques
A. Florio Interactive Rendering Techniques for Focus+Context Visualization of virtual 3D Indoor Models 12
Combination of techniques
All the implemented Focus+Context visualization techniques used simultaneously

13. Demo
A. Florio Interactive Rendering Techniques for Focus+Context Visualization of virtual 3D Indoor Models 13

14. Possible applications
A. Florio Interactive Rendering Techniques for Focus+Context Visualization of virtual 3D Indoor Models 14
Visualization for facility/disaster management:
 Render with focus the elements which should be managed
or taken into account
 Render as context the spatially related elements
 Cut away the unnecessary or occluding elements
Possible visualization in facility management Possible visualization in disaster management

15. Performance evaluation
A. Florio Interactive Rendering Techniques for Focus+Context Visualization of virtual 3D Indoor Models 15
Model
# lines 82237 98515 62678 49675 1845439
loading time 19 s 20 s 21 s 13 s 83 min
frame rate (LOD4) 8 fps 9 fps 3 fps 3 fps 0,12 fps
frame rate (LOD3) 17 fps 24 fps 6 fps 10 fps 0,47 fps
IFC elements 117 92 483 782 14882
drawables 17201 24148 47134 15932 1504707
Measurements on:
3.1 GHz Intel® Core™ i5-2400 processor
8GB RAM
NVIDIA GeForce GT630 with 2GB video memory
Windows 7 Enterprise 64-bit
 Performance depends on:
 Quantity of elements
 Complexity of elements
 Quality of the dataset

16. Future work
A. Florio Interactive Rendering Techniques for Focus+Context Visualization of virtual 3D Indoor Models 16
Storey-based LODs
Focus lens
«X-ray» lens
Clipping volumes

17. Conclusions
A. Florio Interactive Rendering Techniques for Focus+Context Visualization of virtual 3D Indoor Models 17
 Semantic-based Focus+Context visualization:
 Hide or make only slightly visible entire types of elements
 Facilitates perception of important scene elements
 Retain reference objects as context to spatially relate
 Interactive rendering:
 Configuration settings can be changed at runtime
 View-dependent visualization (automatic exploded views)
 Tool for effective exploration of 3D indoor models
 Sufficient rendering performance, space for improvements

18. Questions?
A. Florio Interactive Rendering Techniques for Focus+Context Visualization of virtual 3D Indoor Models 18
Thank you for your attention!