Searching the Ogre forums, several people have tried to use Ogre as the rendering engine for the ARToolkit - some successfully, some not. Here are a couple of relevent message threads:
- - http://www.ogre3d.org/phpBB2/viewtopic.php?p=163290
- http://www.ogre3d.org/phpBB2/viewtopic.php?t=17725
What I've done so far:
- - installed ARToolkit (original) and ran the included demo applications.
- used the ARToolkit's calibration programs to obtain a camera calibration file specific to my Logitech QuickCam Orbit (ARToolkitPlus is able to read these calibration files).
- installed and built ARToolkitPlus
- ARToolkitPlus comes with a simple test application and sample image. I confirmed that the test image is "trackable".
- printed out my own marker (from the ARToolkitPlus), glued it to a piece of cardboard, captured a frame from my webcam and hacked the demo app to check that I could "track" this single image.
- To bring the webcam images into Ogre. I used Timme's plug-in, http://www.ogre3d.org/phpBB2/viewtopic.php?t=16572. It offers notification of a new frame's arrival via a listener class. It's in this listener class constructor that I instantiate the ARToolkitPlus, and the "new frame" method that I search for the marker card.
- Combined, I now have a simple Ogre application with the webcam showing up as a background (see http://www.ogre3d.org/wiki/index.php/Di ... ackgrounds) and a small test mesh being moved around based on calculations coming from ARToolkitPlus.
I.e., the camera/world according to Ogre and that being used by the ARToolkitPlus don't coincide. As a rough first go, I simply set the camera as:
Code: Select all
virtual void createCamera(void)
{
mCamera = mSceneMgr->createCamera("SceneCamera");
mCamera->setPosition(Vector3(0,0,0));
mCamera->lookAt(Vector3(0,0,-5)); // back along -ve z axis
mCamera->setNearClipDistance(0.01);
// vertical opening angle of webcam measured roughly as 85cm at a distance of 160cm distant
// let Ogre calculate horizontal FOV from viewport aspect ratio
mCamera->setFOVy(Radian(0.5163));
}
Code: Select all
float* mv = (float*) (mTracker->getModelViewMatrix() );
Ogre::Vector3 position = Ogre::Vector3(-*(mv+12), *(mv+13), -*(mv+14));
std::cout << "Position: " << position << std::endl;
mNode->setPosition(position);
Part of the mismatch is coming from ARToolkitPlus. The following image shows the marker tile held at the position that gives (x,y) coordinates of (0,0).
The calculated modelview matrix is
Code: Select all
Matched marker: 0 with confidence: 100
-0.8475 0.0245 -0.5302 0.0000
0.0070 0.9994 0.0349 0.0000
0.5307 0.0259 -0.8472 0.0000
0.0051 0.0057 1.6646 1.0000
Position: Vector3(-0.00508792, 0.00572599, -1.66464)
With this tracking at least partly correct, let's consider rotations. Begin by replacing the tiny marker with a 0.1^3 cube sized to match the marker tile. For orientation, we follow haffax's advice (http://www.ogre3d.org/phpBB2/viewtopic.php?p=163290) and convert the ARToolkitPlus modelview matrix into an Ogre quaternion:
Code: Select all
float* mv = (float*) (mTracker->getModelViewMatrix() );
Ogre::Vector3 x = Ogre::Vector3(*(mv+0), *(mv+1), *(mv+2));
Ogre::Vector3 y = Ogre::Vector3(*(mv+4), *(mv+5), *(mv+6));
Ogre::Vector3 z = Ogre::Vector3(*(mv+8), *(mv+9), *(mv+10));
Ogre::Quaternion orientation = Ogre::Quaternion(x.normalisedCopy(), y.normalisedCopy(), z.normalisedCopy());
mNode->setOrientation(orientation);
Rotations are obviously being calculated but two of the directions are reversed. This is where I'm currently up to ...
I appreciate your help so much, I'm at work and I get scared a little with Ogre and OpenCV (is the first time I code in a 3D engine). 
Thanks a lot for your answer.
