用一张图片来修改osgViewer的背景

程序员文章站 2022-05-31 10:01:58

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由于刚开始学习OSG的内容，对相机的理解并不是太深刻，工作中也出现了这个需求，于是决定好好研究一下。对于修改背景图片这个知识点确实不是太难，但是由于之前对于相机的理解太浅，所以这次还是收获很大的。主要是学习了《OSG视频》之后，自己凭借理解有重新编写出的Demo程序，实现效果还可以。下面给出创建背景文理相机的具体代码（开发环境：VS2013+Qt5.7.0+OSG3.4.0）：

osg::Camera* createBackground(QString imageFilePath)
{
    osg::ref_ptr<osg::Camera> camera = new osg::Camera;
    camera->setProjectionMatrixAsOrtho2D(0, 800, 0, 600);
    camera->setClearMask(GL_DEPTH_BUFFER_BIT);
    camera->setViewport(0, 0, 800, 600);
    camera->setViewMatrix(osg::Matrix::identity());
    camera->setAllowEventFocus(false);
    camera->setRenderOrder(osg::Camera::PRE_RENDER);
    camera->setReferenceFrame(osg::Transform::ABSOLUTE_RF);

    osg::ref_ptr<osg::Geode> geode = new osg::Geode;
    camera->addChild(geode);

    osg::ref_ptr<osg::Geometry> gm = new osg::Geometry;
    geode->addDrawable(gm);
    geode->getOrCreateStateSet()->setMode(GL_LIGHTING, osg::StateAttribute::OFF);
    osg::ref_ptr<osg::Vec3Array> vertex = new osg::Vec3Array;
    vertex->push_back(osg::Vec3(0, 0, 0));
    vertex->push_back(osg::Vec3(800, 0, 0));
    vertex->push_back(osg::Vec3(800, 600, 0));
    vertex->push_back(osg::Vec3(0, 600, 0));
    gm->setVertexArray(vertex);

    osg::ref_ptr<osg::Vec3Array> normal = new osg::Vec3Array;
    normal->push_back(osg::Vec3(0, 0, 1));
    gm->setNormalArray(normal);
    gm->setNormalBinding(osg::Geometry::BIND_OVERALL);

    osg::ref_ptr<osg::Vec2Array> coord = new osg::Vec2Array;
    coord->push_back(osg::Vec2(0, 0));
    coord->push_back(osg::Vec2(1, 0));
    coord->push_back(osg::Vec2(1, 1));
    coord->push_back(osg::Vec2(0, 1));
    gm->setTexCoordArray(0, coord);
    gm->addPrimitiveSet(new osg::DrawArrays(osg::DrawArrays::QUADS,0,4));

    osg::ref_ptr<osg::Image> image = osgDB::readImageFile(imageFilePath.toStdString());

    osg::ref_ptr<osg::Texture2D> t2d = new osg::Texture2D;
    t2d->setImage(image);
    gm->getOrCreateStateSet()->setTextureAttributeAndModes(0, t2d, osg::StateAttribute::ON);

    return camera.release();
}