qt3d - QScreenRayCaster 未找到实体。我做错了什么？

Question

Qt3D 中新 QScreenRayCaster 的描述看起来正是我想要使用的，但我无法让它为我工作。我想在初始化过程中我需要做一些事情，但我在网上找不到任何示例来为我指明正确的方向。我写了一个非常简单的程序来测试这个功能。它在窗口的中心绘制一个单位球体，然后在中心点触发一个 QScreenRayCaster，据我所知，它应该返回一个命中列表，只有在我的程序中它没有。任何帮助或见解表示赞赏。

MyQt3DWindow:: MyQt3DWindow(QScreen *screen)
    : Qt3DExtras::Qt3DWindow(screen)
{
    // scene
    Qt3DCore::QEntity *rootEntity = new Qt3DCore::QEntity;
    Qt3DRender::QMaterial *material = new Qt3DExtras::QPhongMaterial(rootEntity);
    Qt3DCore::QEntity *sphereEntity = new Qt3DCore::QEntity(rootEntity);
    Qt3DExtras::QSphereMesh *sphereMesh = new Qt3DExtras::QSphereMesh;
    sphereEntity->addComponent(sphereMesh);
    Qt3DCore::QTransform *sphereTransform = new Qt3DCore::QTransform;
    sphereEntity->addComponent(sphereTransform);
    sphereEntity->addComponent(material);

    // Camera
    Qt3DRender::QCamera *camera = this->camera();
    camera->lens()->setOrthographicProjection(-2, 2, -2, 2, 0.1f, 1000.0f);
    camera->setPosition(QVector3D(0, 0, 40.0f));
    camera->setViewCenter(QVector3D(0, 0, 0));

    // picker
    m_screenRayCaster = new Qt3DRender::QScreenRayCaster(rootEntity);
    m_screenRayCaster->setRunMode(Qt3DRender::QAbstractRayCaster::SingleShot);
    Qt3DRender::QLayer *pickableLayer = new Qt3DRender::QLayer(rootEntity);
    m_screenRayCaster->addLayer(pickableLayer);
    sphereEntity->addComponent(pickableLayer);

    this->setRootEntity(rootEntity);
    this->setGeometry(100, 100, 400, 400);

    // and call the caster after a short delay
    QTimer::singleShot(1000, this, SLOT(testRayCaster()));
}

void MyQt3DWindow::testRayCaster()
{
    m_screenRayCaster->trigger(QPoint(200, 200));
    Qt3DRender::QAbstractRayCaster::Hits hits = m_screenRayCaster->hits();
    qDebug() << "Hits found = " << hits.size() << "\n";
}

class MyQt3DWindow: public Qt3DExtras::Qt3DWindow
{
Q_OBJECT
public:
    MyQt3DWindow(QScreen *screen = nullptr);

public slots:
    void testRayCaster();

private:
    Qt3DRender::QScreenRayCaster *m_screenRayCaster;
};

Answer 1

您必须将光线转换器作为组件添加到根实体。您还应该将插槽连接到光线转换器的 hitsChanged() 函数并从那里显示命中。这样你就可以确定施法者已经计算了命中。

顺便说一句:如果您对 Qt3D 有疑问，请查看他们的 github 存储库并查找 test folder .里面有一个包含手动测试的文件夹，您可以在其中看到 Qt3D 的大部分功能。