Develop a working osgART application

What is a Scene Graph?

Tree-like structure for organising a virtual world, e.g. VRML
Hierarchy of nodes that define: Groups (and Switches, Sequences etc…) Transformations, Projections, Geometry …

And states and attributes that define:

•  Materials and textures
•  Lighting and blending

Benefits for performance

•   Structuring data facilitates 
• optimization:- Culling, state management, etc

What is a Open Scene Graph (OSG)?

Open-source scene graph implementation

Based on OpenGL

Object-oriented C++ following design pattern principles

Used for simulation, games, research, and industrial projects

Maintained by Robert Osfield | Documentation project: www.osgbooks.com

Uses the OSG Public License (similar to LGPL)

What is a osgART?

OSG + ARTookit = osgART

osgART adds AR to Open Scene Graph

Current version 2.0, Open Source

To add Video see-through AR:

•  Integrate live video
•  Apply correct projection matrix
•  Update tracked transformations in real-time

Develop a working osgART application from scratch?

Use ARToolKit 2.72 

     library for tracking and 

     video capture

Install OSG

Tutorial 1 : Basic OSG Viewer | OSG 

Install osg (.exe) to your computer

Run basic viewer - located in osg folder in C:\\Program Files (Windows)

Tutorial 2: Adding Video | OSG + ARToolkit

Add a video plugin

Load, configure, start video capture…

Add a video background

Create, link to video, add to scene-graph

Tutorial 3: Tracking | OSG + ARToolkit

Add a Tracker plugin

 Load, configure, link to video

 Add a Marker to track

 Load, activate

 Tracked node

 Create, link with marker via tracking callbacks

 Print out the tracking data

Tutorial 4: Adding Content | OSG + ARToolkit

Now put the tracking data to use!

Add content to the tracked transform 

Basic cube code

e.g. Wavefront (.obj), OpenFlight (.flt), 3D Studio (.3ds), COLLADA

Replace the simple cube with a 3D model

Models are loaded using the osgDB::readNodeFile() function

OSGART sample project by other researchers

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Augmented Reality Categories

Optical See-Through HMD

One of the devices used to merge real and virtual environment is an Optical See-Through HMD. It allows the user to interact with real world using optical technologies to superimpose virtual objects on the real world, as stated by Azuma (1997) and agreed by Ajune et al (2008).  The optical see-through is used transparent HMD to produce the virtual environment directly to the real world. Optical see-through HMDs’ function is placing optical combiners in front of the user's eyes. 

Video See Through

Again, as mentioned by Azuma (1997), Video see-through HMDs are able to give user a real world sight by combining a closed-view HMD with one or two head-mounted video cameras, due to this mixture give user a view of real world and virtual world in real-time through the monitors in front of the user's eyes in the closed-view HMD. Figure 2.4 shows a conceptual diagram of a video see-through HMD. Figure 2.5 shows a video see-through HMD. Video composition can be done using chroma-key or depth mapping (Silva, Oliveira & Giraldi 2003)

Virtual Retinal Systems

Virtual Retinal Systems aim to produce a full color, wide field-of-view, high resolution, high brightness and low cost virtual display (Ishii, 1994). This technology can be used in wide range of applications from head-mounted displays for military or aerospace applications to medical purposes. The Virtual Retinal Display (VRD) uses a modulated beam of light (from an electronic source) directly onto the retina to produce a rasterized image, as stated by Azuma (1997). 

Monitor Based AR

Monitor based AR uses one or two video cameras to view the environment where the cameras may be static or mobile. The video was produced by combining the video of the real world and graphic image generated by a scene generator and the product was shown to user by using monitor device. The display devices are not wearing by the user but when the images are presenting in the stereo on the monitor, it requires user to wear the display devices such as stereo glasses. 

Recently, AR is widely being used in many applications such as education, entertainment, simulation and games. In virtual heritage, AR is used to enhance the overall experience of the visitor of a cultural heritage site. Furthermore, with the interactive, realistic and complex AR system, it can enhance, motivate and stimulate students’ understanding of certain events

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