Engineering and Augmented Reality Tour Guide

We describe a mobile augmented reality system intended for in situ reconstructions of archaeological sites. The evolution of the system from proof of concept to something approaching a satisfactory ergonomic design is described, as are the various approaches to achieving real-time rendering performance from the accompanying software. Finally, some comments are made concerning the accuracy of such systems.

Transcript

1. Engineering an Augmented Reality Tour Guide Panagiotis D. Ritsos, David J. Johnston, Christine Clark and Adrian F. Clark VASE Lab, Department of Electronic Systems Engineering University of Essex IEE Eurowearable, Birmingham, 2003
2. Talk Outline Augmented Reality in General Project Definition 1st Generation system Limitations and Solutions 2nd Generation system Conclusions
3. The Concepts Augmented Reality An augmented reality system superimposes virtual information, usually computer generated models, on top of the real environment in order to enhance the latter. The user sees a composite image of the real and the virtual world. Context Awareness “any information that can be used to characterise the situation of an entity, where an entity can be a person, place, physical or computational object” - Dey & Abowd (1999)
4. The Application Augment the Gosbecks Temple en situ using a 3D reconstruction of the temple Use a Wearable Computer to Interface with a GPS and an HMD tracker to extract position and orientation information Render the model according to this information Use a Distributed instead of a Centralized system No centralized rendering – each wearable renders its own view This enables more wearables to roam in our virtual space Eliminates the overhead of transmitting the 3D information to each wearable
5. The Virtual Temple The Gosbecks Park and the Temple to Claudius We created a 3D Model of the temple using OpenGL
6. The Tour Guide in a few words The user roams with the wearable on the field Position extracted from the GPS unit Orientation extracted from the HMD tracker – Context Awareness A virtual model of the temple is projected through the HMD - Augmented Reality Gosbecks is ideal for such an application because it is relatively flat and with no surrounding buildings – the GPS unit can ‘see’ a large number of satellites
7. Wearable Computers A Wearable computer is usually belt-worn or carried in some form of a jacket vest or backpack It has the processing power of a modern laptop Components usually include a Head Mounted Display, and Input device such as a ‘chord keyboard’ Extra in most Mobile AR applications is a Global Positioning (GPS) Unit Camcorder batteries used for power
8. Remus Wearable – 1st Generation system Pentium 266, 64 MB of RAM, generic VGA, 4 serial ports, USB, Audio and PC Card adapter to be used with WLAN cards Constructed from PC/104 cards All encompassed in an aluminium box Garmin GPS unit, Orientation Tracker on the HMD 4.9 Kg and operational for 45 min
9. Limitations of initial configuration Very Slow refresh rate – No 3D acceleration Accuracy of GPS Bulky system – can be tiring Power supply is not adequate –2 hours of operation are required Requires a simpler interaction mechanism than a chord keyboard
10. GPS – Limitations It is not accurate enough – Drift with time Differential GPS could improve performance but not to the desired level Ideally an accuracy of 20 cm (position) is required for ‘True’ AR Orientation requirements not so stringent – about 5o error is acceptable
11. Proposed solutions Computer is integrated to a vest Optimisation of the model Use View Frustum Culling to render only visible objects Employ levels of detail processing – replace distant objects with images Localisation? GPS is adequate for a demonstration but not for a commercially viable system
12. View Frustum Culling A technique used in 3D games like First Person Shooters (Quake, Unreal etc.) OpenGL renders all objects requested – even those that are not always visible! View Frustum Culling enables us to ‘cull’ objects that are not visible
13. Levels Of Detail Simple mechanisms for further optimization Distance Test – If something is very distant, do not draw it! – In the colonnades we draw one row (front) instead of two If Something is moderately away, draw it without detail – This reduces polygon count significantly since each column has at least 4 extra cylinders
14. Romulus Wearable – 2nd Generation System Mini – ITX based system Faster, simpler, extra multimedia features, comparable power requirements – increased fun factor! Large upgrade potential Large support from online community due to platforms popularity And recently … 3D hardware support! Integrated into a Photographers Vest – easier to wear and carry
15. Romulus Wearable – Part 2 Via C3 1Ghz Nehemiah VIA ProSavage CLE266 chipset 512 MB DDR memory 20 GB Hard Disk Soundcard, Ethernet 802.3, 2 USB, 2 Serial, 1 I2C Aluminium casing – compatible with all mini-ITX modules Garmin GPS Unit, Virtual I/O HMD with orientation tracker Netgear 802.11b wireless LAN interface Comparable Power requirements to Remus, with 2A max drain, 1.3 average System powered from a custom battery pack of 10 1.2 Volt NiMH cells – two pack to be used in finalised system.
16. System Performance Evaluation System Testing is currently performed Graphics speed significantly better – 7 frames per second average, 15 fps maximum. System is much lighter than alternatives, yet its performance as far as graphics are concerned is more than adequate for demonstration purposes Next step is to improve the interaction mechanisms – use a single button interface to restart the application The system has increased upgradeability potential than other embedded boards alternatives – online community provides significant feedback – drivers constantly updated. Yet…ideally it should be smaller!
17. Conclusions Augmented Reality prototypes provide adequate demonstration systems – 3D rendering capability and GPS accuracy the major drawback Commercially viable systems require more accurate, smaller, faster and lighter wearable computers Hardware implementation of such a system is feasible – similar to a laptop with good multimedia features Localisation techniques require further investigation Power consumption problems similar to modern laptops