Interactive Construction Process Visualization in Outdoor Augmented Reality

 

The objective of this research is to develop an extensible and scalable Augmented Reality (AR) platform to facilitate the visualization of simulated construction operations in an outdoor augmented environment.

 

This platform is both equipped with devices capable of rapid position calculation and image rendering including an interface for external input (i.e. both user commands and an unaltered video capturing of the environment), and an interface to display the final augmented view to the user. To create a realistic mixed view of the virtual CAD models and real world video captures, the biggest challenge is to achieve a steady state of virtual objects registered in the coordinates of the real world and further maintain this registration throughout the animation of simulated operations. This in fact requires the coordinate system of the augmented world to accurately coincide with the one of the real world. The superimposed images must stay fixed to their real world location as the user is moving so that augmented graphics always appear at the same physical location.

 

To ensure continuous operation without restricting mobility, the proposition of designing a mobile outdoor backpack is also introduced in this research. Such a backpack must provide enough secure room for hardware components supported by external power sources. The backpack design should also take into account the ergonomic factors to avoid user discomfort after long periods of operation. The proposed AR backpack in this research takes advantage of a modular design in which every component can be easily upgraded and/or replaced by a newer alternative as long as it follows a certain data transmission standard and commonly accepted rules of device communication methods.

 

Another critical component in such a mobile AR architecture is a robust software interface between the computing source (e.g. a laptop computer) and the peripheral devices.  This interface facilitates the acquisition of positioning and orientation data in a global space.  It also captures live video of the surroundings, and includes a video compositor engine that renders virtual objects into the real world scenes and displays the combined image to the user in real time. The software interface in this research takes advantage of an Object-Oriented Design (OOD) in which every element is assigned a module in the code to communicate with other devices. This way, future replacements, modifications, and upgrades of any peripheral component will not affect the overall integrity of the system. In other words, each code module is absolutely device independent as long as its corresponding device provides the system with output that follows a standard format.

 

Related issues being addressed during the course of this research include but not limited to:

• Tracking and registration of CAD objects in global coordinate system

• Manipulation of an arbitrary number of virtual objects performing an operation over a real background

• Establishing modular communication methods for data acquisition from the geo-positioning and orientation tracking devices

• Integration with project schedule and electronic terrain maps

• Design and implementation of a general-purpose software interface

• Design of an ergonomic mobile AR backpack