Using ARDev as a library

This page describes the use of ARDev as a library integrated into an exisitng application. This usage of the system also allows for the powerful creation of custom visualisations, and also for highly customised uses of the library.

The debugging space concept is one example of a custom use of the ARDev library there are many more possibilities both using robots, and also in other application areas.

Detailed documentation of the individual classes is described in the classes page. This is generated with doxygen directly from the source, so should be kept up to date. The purpose of this page is to give an overview of how the library is expected to be used, hoepfully people will also start using it in some unexpected ways, in which case this page can be used as a starting point to break the mold from.

The ARDev Library Basics

The ARDev system is designed to be very flexible and modular, designed with the goal of supporting a wide range of AR hardware setups. The three specific setups in mind are, video see through AR, both head mounted and fixed camera, and optical see through.

There are seven key objects that are used in the AR system, any object that is optional has a NULL implementation that can be used as a place holder. The key objects are:

ARDev: this manages the AR session and performs high level control operations.
OutputObject: Creates the display and manages the OpenGL context
CaptureObject: Grabs the real world frame, NULL for optical see through
FrameProcessObject: Allows for pre and post processing of frames, particularly for fiducial tracking.
CameraObject: Encapsulates the intrinsic camera parameters, this can work with the calibration utility, or alternatively existing calibration applications can be used.
PositionObject: Defines a 3d position and orientation in space, these can be chained together to create a tree structure.
RenderObject: Responsible for the actual rendering of the virtual object.

The two key objects from this list are the ARDev object which manages the Augmented reality system and the OutputObject that manages the individual rendering pipeline for a display.

Using the library

This section provides a fairly simple example of using the toolkit in an application. This example will look at rendering the openGL teapot on a fiducial marker in the environment. In this case we are using a fixed camera with a static calibration.

This first step is to set up the AR environment, we need to have some standard includes:

#include <ardev/ardev.h>
#include <ardev/capture.h>
#include <ardev/output_x11.h>
#include <ardev/render_base.h>

It is probably a good idea to turn on a reasonable level of debugging.

        ARDev::DebugLevel = ARDBG_INFO;

You could also set this to ARDBG_VERBOSE for more debugging info.

Then we get into the real initialisation, first set up the capture object, we are going to use firewire in this case.

        CaptureObject * cap = new CaptureDC1394();

Next we initialise a static camera object based on a static calibration.

        ARCamera arcam("static.calib");
        CameraConstant cam(arcam);

        PositionConstant * CamPosition;
        ARPosition CameraOffsetConst(arcam.Origin,arcam.Direction);
        CamPosition = new PositionConstant(CameraOffsetConst);
        CamPosition->Initialise();

Now that we have the basics for grabbing a realworld snapshot we can create the output object and initialise the display.

        OutputObject * out = new OutputX11((CaptureObject*)cap,&cam,CamPosition,800,600,":0",FullScreen);

Having created our display we can now can inistialise the ARDev object

        ARDev::Start(out,"overhead");

At this stage we should now have a live stream from the camera, albiet an overly complex way of getting this if that was all we wanted. So now we want to render our augmented data. So the first step is to create the fiducial tracker and register it with the system.

        ARToolKitPlusPreProcess * artkp_pre;
        artkp_pre = new ARToolKitPlusPreProcess(cam);
        artkp_pre->Initialise();

        out->AddPre(artkp_pre);
        
        PositionObject * RobotPos = new ARToolKitPlusPosition(*artkp_pre,11,0.31);
        RobotPos->Initialise();

And now to create the render object.

        ARColour Blue(0,0,255,0);
        RenderTeapot Teapot(Blue,0.01);

Finally we create the link between the position object and render object and add them to the render list.

        ARDev::Add(RenderPair(&Teapot,RobotPos),"overhead");

After this you would have your normal application code, once you are ready to stop the AR rendering simply call the following.

        ARDev::Stop("overhead");

Extending ARDev

To add new objects to ARDev simply subclass the base for the object type and implement the requried methods. The methods that are required will vary from class to class but there generally are only one or two.

The new objects can then simply be used as described above.

Generated on Sat May 12 15:25:43 2007 for ardev by

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