如何在运行时在 openscenegraph 上更改背景

Question

我尝试在查看器上添加 3d object 并动态更改背景。我使用 opencv VideoCapture.

捕获网络摄像头

我做了以下步骤：

打开视频捕获并获取帧
创建 openscenegraph root
添加一个child到root（从.osg文件读取3d object）
为背景创建 texture2d object
设置背景图片
创建相机查看背景
将摄像头添加到root
查看器设置数据(viewer.setScenedat(root))
运行 viewer.run()

这些步骤将第一帧添加为背景并向场景添加 3d object。但我不能改变每一帧的背景。我该怎么做？

代码：

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();
}

此代码动态更改背景。

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