Tracking 3D + rotation matrix

edit

Thank you so much , i tried to compile the tutorial code of POSIT it works with only a specific image for a cube : "IplImage img = cvLoadImage( "C:\img.jpg" );". I need image from a capture video not from a known image : "IplImage *img; // capture from video device CvCapture capture = cvCaptureFromCAM(0); // create a window to display the images cvNamedWindow("mainWin", CV_WINDOW_AUTOSIZE);

while(1)
{
    // retrieve the captured frame
    img=cvQueryFrame(capture);..."

and then how can i track the cube and use the POSIT algorithm

As I've said before, the tracking is the most difficult part... Start using a different color for each corner, and after that, if you are not using a cube, you could try different approach, like SIFT/SURF/ORB/.. and find homography like in this tutorial http://docs.opencv.org/doc/tutorials/features2d/feature_homography/feature_homography.html But take care that the object must not be a plane for POSIT!