How to change background at runtime on openscenegraph

Question

I try to add an 3d object on viewer and change background dynamically. I capture webcam using opencv VideoCapture.

I did below steps :

1. Open video capture and get frame

2. Create openscenegraph root

3. Add a child to root ( read from .osg file 3d object)

4. Create a texture2d object for background

5. Set image of background

6. Create a camera to view background

7. Add camera to root

8. Set data of viewer (viewer.setScenedat(root))

9. Run viewer.run()

   These steps add first frame as background and add a 3d object to scene. But I can't change background each frame. How can I do it?

Code :

cv::VideoCapture cap(0);  
cv::Mat frame;

if(!cap.isOpened())  
{
    std::cout << "Webcam cannot open!\n";
    return;
}  

osgViewer::Viewer viewer;
osg::ref_ptr<osg::Group> root = new osg::Group();
osg::ref_ptr<osg::Texture2D> bg = new osg::Texture2D();

root->addChild(osgDB::readNodeFile("object.osg"));
bg->setFilter(osg::Texture::FilterParameter::MIN_FILTER, osg::Texture::FilterMode::LINEAR);
bg->setFilter(osg::Texture::FilterParameter::MAG_FILTER, osg::Texture::FilterMode::LINEAR);    
bg->setDataVariance(osg::Object::DYNAMIC);

cap >> frame;
osg::ref_ptr<osg::Image> osgImage = new osg::Image;
osgImage->setImage(frame.cols, frame.rows, 3,
    GL_RGB, GL_RGB, GL_UNSIGNED_BYTE,
    (uchar*)(frame.data),
    osg::Image::AllocationMode::NO_DELETE, 1);
bg->setImage(osgImage);

osg::ref_ptr<osg::Camera> bg_cam = new osg::Camera();
bg_cam->setProjectionMatrixAsOrtho2D(-0.5, 0.5, -0.5, 0.5);
bg_cam->setViewMatrixAsLookAt(
    osg::Vec3(0.5, 0.5, -1.0),
    osg::Vec3(0.5, 0.5, 0.0),
    osg::Vec3(0.0, -1.0, 0.0)
    );
bg_cam->setRenderOrder(osg::Camera::PRE_RENDER);
bg_cam->setReferenceFrame(osg::Camera::ABSOLUTE_RF);
bg_cam->addChild(initializeBackground(bg));
root->addChild(bg_cam);

viewer.setSceneData(root);
viewer.getCamera()->setProjectionMatrixAsPerspective(
    40., 1., 1., 100.);
viewer.getCamera()->setClearMask(GL_DEPTH_BUFFER_BIT);
viewer.getCamera()->setClearColor(osg::Vec4(1.0, 0.0, 0.0, 1.0));
  
viewer.run();

Answer 1

viewer.getCamera()->setClearMask(GL_DEPTH_BUFFER_BIT);
viewer.getCamera()->setClearColor(osg::Vec4(1.0, 0.0, 0.0, 1.0));
 bg->setDataVariance(osg::Object::DYNAMIC);
viewer.realize();  // set up windows and associated threads. 

while(!viewer.done())
{
    cap >> frame;     

    osg::ref_ptr<osg::Image> osgImage = new osg::Image;
    osgImage->setImage(frame.cols, frame.rows, 3,
        GL_RGB, GL_BGR, GL_UNSIGNED_BYTE,
        (uchar*)(frame.data),
        osg::Image::AllocationMode::NO_DELETE, 1);
    bg->setImage(osgImage);

    viewer.frame();
}   

This code changes background dynamially.