The iHelmet: An AR-enhanced Wearable Display for BIM Information - Mobile and Pervasive Computing in Construction - page 154

namely the user interface layer, the data processing layer and the data storage layer.
Each layer is composed of major units or functions, shown as blocks in Figure 8.1.
The arrows used to connect blocks in Figure 8.1 represent the direction of data or
message processing.
The user interface layer is composed of three modules: the display module, the
positioning module, and the manipulation module. This layer sends manipulations
and interactions to the image-based model from the user, and sends visual feedback
to the user through the display module.
The data processing layer is composed of an image-based model, which is a
component of the information integration module. According to the manipulation
command sent from the user, image-based models make the corresponding changes.
As the image-based model changes, the projection will change simultaneously.
The data storage layer is composed of a BIM model, another component of the
information integration module. The BIM model is used for saving all the
components of the room and information about the components. In this system
framework, the user can directly manipulate the image-based model and receive
immediate visual feedback.

8.2.2 Development environment

In this research, an iPod Touch 1 and the Optoma PK101 2 projector were selected,
using iPhone SDK3.0 3 and Objective-C 4 as programming languages for the
improvement of iHelmet's environment through building many visual effects
and interactive approaches.
The iPod Touch was originally designed as a portable media player, a personal
digital assistant, and a Wi-Fi mobile platform. The reason for the choice of the iPod
Touch was its compact size and light weight (W 110mm,

115 g), its multitouch capabilities and its accelerometer (Figure 8.2). Through the
iPod Touch, users can easily employ touch or gesture controls to command
manipulations.
The reason for choosing the Optoma PK101 as the projector in the iHelmet was
also for its compact size and light weight (W

H D: 61.8 8.5

103mm, 114g),
and rechargeable long-lasting battery (averaging three hours usage time)
(Figure 8.3). With this thin projector, users can project information from mobile
devices more conveniently.
The software development environment used the iPhone SDK3.0 and Objective-
C, running on a Mac operating system. iPhone SDK allows developers to develop
applications for the iPod Touch and provides interactive functions for develop-
ment. Objective-C is a reflective, object-oriented programming language, and is
used primarily on Apple”s Mac OS X and iPhone OS.

H D: 50 15

1 The iPod Touch is a portable media player, personal digital assistant, and Wi-Fi mobile platform
designed and marketed by Apple Inc.
2 The Optoma PK101 is a pico pocket projector published by Optoma Technology, Inc.
3 iPhone SDK is a software development kit developed by Apple Inc.
4 Objective-C is the primary language used for Apple's Cocoa API, and it was originally the main
language on NeXT's NeXTSTEP OS.