homography screenReality

homography_screenreality

//-- Matrix
    float modelview[16];
    float projection[16];
    glGetFloatv (GL_MODELVIEW_MATRIX, modelview);
    glGetFloatv (GL_PROJECTION_MATRIX, projection);
    cv::Mat modelM(4,4,CV_32FC2,modelview);
    cv::Mat projM(4,4,CV_32FC2,projection);
    cv::Mat M = projM*modelM;

    std::cout<<M<<std::endl;

    // HOMOGRAPHY CORRECTION            //might only need 3 points
    //-- opengl camera center
    float cx = (float)windowWidth/40.0;
    float cy = (float)windowHeight/40.0;
    //-- space corners coordinates
    float p0[4]={cx,cy,0,1};
    float p1[4]={-cx,cy,0,1};
    float p2[4]={-cx,-cy,0,1};
    float p3[4]={cx,-cy,0,1};
    //-- space corners matrix
    cv::Mat P0(4,1,CV_32FC2,p0);
    cv::Mat P1(4,1,CV_32FC2,p1);
    cv::Mat P2(4,1,CV_32FC2,p2);
    cv::Mat P3(4,1,CV_32FC2,p3);
    //-- projected corners matrix
    cv::Mat Q0 = M*P0;
    cv::Mat Q1 = M*P1;
    cv::Mat Q2 = M*P2;
    cv::Mat Q3 = M*P3;
    //-- projected corners divided by z
    Q0 /= Q0.at<float>(2.0,0.0);
    Q1 /= Q1.at<float>(2.0,0.0);
    Q2 /= Q2.at<float>(2.0,0.0);
    Q3 /= Q3.at<float>(2.0,0.0);
    //-- space corners points
    std::vector<cv::Point2f> ps;
    ps.push_back(cv::Point2f(cx,cy));
    ps.push_back(cv::Point2f(-cx,cy));
    ps.push_back(cv::Point2f(-cx,-cy));
    ps.push_back(cv::Point2f(cx,-cy));
    //-- projected corners points
    std::vector<cv::Point2f> qs;
    qs.push_back(cv::Point2f(Q0.at<float>(0.0,0.0),Q0.at<float>(1.0,0.0)));
    qs.push_back(cv::Point2f(Q1.at<float>(0.0,0.0),Q1.at<float>(1.0,0.0)));
    qs.push_back(cv::Point2f(Q2.at<float>(0.0,0.0),Q2.at<float>(1.0,0.0)));
    qs.push_back(cv::Point2f(Q3.at<float>(0.0,0.0),Q3.at<float>(1.0,0.0)));

    //cv::Mat H = cv::findHomography( ps , qs , CV_RANSAC );
    //std::cout<<H<<std::endl;

    //std::cout<<Q0<<std::endl;