如何使用Qt3D库加载和显示搅拌器.obj源文件场景

Question

我试图从搅拌器加载一个.obj源文件，并显示它，LibertStatue.obj是与下面的main.cpp文件位于同一个文件夹中的.obj文件。当我运行这段代码时，我会得到一个空白窗口，我认为它应该显示一个自由女神像，以及一个命令提示符，上面写着QObject::connect(opneglcontext，未知)无效的nullptr参数。我在上使用。

我从这里下载了自由女神像的.obj文件：https://free3d.com/3d-model/statue-of-liberty-73656.html。

#include <QGuiApplication>
#include <Qt3DExtras/QPhongMaterial>
#include <Qt3DExtras/Qt3DWindow>
#include <Qt3DExtras/QOrbitCameraController>
#include <Qt3DRender>

int main(int argc, char *argv[])
{
    QGuiApplication app(argc, argv);
    QUrl data = QUrl::fromLocalFile("LibertStatue.obj");
    Qt3DExtras::Qt3DWindow view;

    Qt3DCore::QEntity *rootEntity = new Qt3DCore::QEntity;
    Qt3DCore::QEntity *flyingwedge = new Qt3DCore::QEntity(rootEntity);

    Qt3DExtras::QPhongMaterial *material = new Qt3DExtras::QPhongMaterial();
    material->setDiffuse(QColor(254, 254, 254));

    Qt3DRender::QMesh *flyingwedgeMesh = new Qt3DRender::QMesh;
    flyingwedgeMesh->setMeshName("FlyingWedge");
    flyingwedgeMesh->setSource(data);
    flyingwedge->addComponent(flyingwedgeMesh);
    flyingwedge->addComponent(material);

    Qt3DRender::QCamera *camera = view.camera();
    camera->lens()->setPerspectiveProjection(40.0f, 16.0f/9.0f, 0.1f, 1000.0f);
    camera->setPosition(QVector3D(0, 0, 40.0f));
    camera->setViewCenter(QVector3D(0, 0, 0));

    Qt3DCore::QEntity *lightEntity = new Qt3DCore::QEntity(rootEntity);
    Qt3DRender::QPointLight *light = new Qt3DRender::QPointLight(lightEntity);
    light->setColor("white");
    light->setIntensity(0.8f);
    lightEntity->addComponent(light);

    Qt3DCore::QTransform *lightTransform = new Qt3DCore::QTransform(lightEntity);
    lightTransform->setTranslation(QVector3D(60, 0, 40.0f));
    lightEntity->addComponent(lightTransform);

    Qt3DExtras::QOrbitCameraController *camController = new Qt3DExtras::QOrbitCameraController(rootEntity);
    camController->setCamera(camera);

    view.setRootEntity(rootEntity);
    view.show();

    return app.exec();
}

Answer 1

问题是setMeshName调用。QMesh C++类的文档具有误导性：setMeshName不是用于为QMesh对象设置名称，而是用于从要加载的OBJ文件中选择哪个几何图形。它的实际行为在相应的QML类型的文档中解释。

因此，您有两个选项:只需删除setMeshName调用，或传递几何学的实际名称，您可以通过使用文本编辑器打开OBJ文件来找到这个名称。

Answer 2

检查您的代码，在我看来，Qt3Dwindow不能单独显示，需要创建一个窗口容器来在Widget (QFrame)中显示Qt3DWindow。

用于测试的典型Qt3D应用程序如下所示：

#include <QApplication>
#include <QDebug>
#include <QFrame>
#include <QVBoxLayout>
#include <QWidget>
#include <QTimer>

#include <Qt3DRender/QCamera>
#include <Qt3DRender/QCameraLens>
#include <Qt3DExtras/Qt3DWindow>
#include <Qt3DExtras/QOrbitCameraController>
#include <Qt3DExtras/QDiffuseSpecularMaterial>
#include <Qt3DExtras/QSphereMesh>

int main(int argc, char* argv[])
{
    QApplication a(argc, argv);

    auto view = new Qt3DExtras::Qt3DWindow();

    auto rootEntity = new Qt3DCore::QEntity();
    view->setRootEntity(rootEntity);

    auto camera = view->camera();
    camera->lens()->setPerspectiveProjection(45.0f, 1., 0.1f, 10000.0f);
    camera->setPosition(QVector3D(0, 0, 5));
    camera->setUpVector(QVector3D(0, 1, 0));
    camera->setViewCenter(QVector3D(0, 0, 0));

    auto camController = new Qt3DExtras::QOrbitCameraController(rootEntity);
    camController->setCamera(camera);

    auto sphereMat = new Qt3DExtras::QDiffuseSpecularMaterial;
    sphereMat->setDiffuse(QColor(Qt::blue));

    auto mesh = new Qt3DExtras::QSphereMesh();
    mesh->setRadius(1);

    auto sphereEntity = new Qt3DCore::QEntity(rootEntity);
    sphereEntity->addComponent(mesh);
    sphereEntity->addComponent(sphereMat);

    auto container = QWidget::createWindowContainer(view);
    QFrame frame;
    frame.setLayout(new QVBoxLayout);
    frame.layout()->addWidget(container);
    frame.resize(QSize(400, 300));

    QTimer::singleShot(100, [&]() {
        camera->viewAll();
    });

    frame.show();
    return a.exec();
}