Qt3D C++实现鼠标左键控制摄像机旋转模型，六视图切换，模型自动旋转

相机旋转具体实现如下：

 trackballcameracontroller.h

#ifndef TRACKBALLCAMERACONTROLLER_H
#define TRACKBALLCAMERACONTROLLER_H

#include 
#include 
#include 
#include 

class TrackballCameraController : public Qt3DExtras::QAbstractCameraController
{
    Q_OBJECT
public:
    Q_PROPERTY(QSize windowSize READ windowSize WRITE setWindowSize NOTIFY windowSizeChanged)
    Q_PROPERTY(float trackballSize READ trackballSize WRITE setTrackballSize NOTIFY trackballSizeChanged)
    Q_PROPERTY(float rotationSpeed READ rotationSpeed WRITE setRotationSpeed NOTIFY rotationSpeedChanged)

    TrackballCameraController(Qt3DCore::QNode *parent = nullptr);

    QSize windowSize() const
    {
        return m_windowSize;
    }

    float trackballSize() const
    {
        return m_trackballSize;
    }

    float rotationSpeed() const
    {
        return m_rotationSpeed;
    }

public slots:
    void setWindowSize(QSize windowSize)
    {
        if (m_windowSize == windowSize)
            return;

        m_windowSize = windowSize;
        emit windowSizeChanged(m_windowSize);
    }

    void setTrackballSize(float trackballSize)
    {
        if (qFuzzyCompare(m_trackballSize, trackballSize))
            return;

        m_trackballSize = trackballSize;
        emit trackballSizeChanged(m_trackballSize);
    }

    void setRotationSpeed(float rotationSpeed)
    {
        if (qFuzzyCompare(m_rotationSpeed, rotationSpeed))
            return;

        m_rotationSpeed = rotationSpeed;
        emit rotationSpeedChanged(m_rotationSpeed);
    }

signals:
    void windowSizeChanged(QSize windowSize);
    void trackballSizeChanged(float trackballSize);
    void rotationSpeedChanged(float rotationSpeed);

protected:
    void moveCamera(const Qt3DExtras::QAbstractCameraController::InputState &state, float dt) override;
    QVector3D projectToTrackball(const QPoint &screenCoords) const;
    void createRotation(const QPoint &firstPoint,
                               const QPoint &nextPoint, QVector3D &dir, float &angle);

private:
    QPoint m_mouseLastPosition, m_mouseCurrentPosition;
    QSize m_windowSize;
    float m_trackballRadius = 1.0f;
    float m_panSpeed = 1.0f;
    float m_zoomSpeed = 1.0f;
    float m_rotationSpeed = 1.0f;
    float m_zoomCameraLimit = 1.0f;
    float m_trackballSize = 1.0f;
};

#endif // TRACKBALLCAMERACONTROLLER_H

trackballcameracontroller.cpp

#include "trackballcameracontroller.h"
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 

TrackballCameraController::TrackballCameraController(Qt3DCore::QNode *parent)
    : Qt3DExtras::QAbstractCameraController (parent)
{
    Qt3DInput::QMouseHandler *mouseHandler = new Qt3DInput::QMouseHandler(this);
    mouseHandler->setSourceDevice(mouseDevice());

    QObject::connect(mouseHandler, &Qt3DInput::QMouseHandler::pressed,
                     [this](Qt3DInput::QMouseEvent *pressedEvent) {
        pressedEvent->setAccepted(true);
        m_mouseLastPosition = QPoint(pressedEvent->x(), pressedEvent->y());
        m_mouseCurrentPosition = m_mouseLastPosition;
    });

    QObject::connect(mouseHandler, &Qt3DInput::QMouseHandler::positionChanged,
                     [this](Qt3DInput::QMouseEvent *positionChangedEvent) {
        positionChangedEvent->setAccepted(true);
        m_mouseCurrentPosition = QPoint(positionChangedEvent->x(),
                                              positionChangedEvent->y());
    });
    //keyboardDevice()->set
}

QVector3D TrackballCameraController::projectToTrackball(const QPoint &screenCoords) const
{
    float sx = screenCoords.x(), sy = m_windowSize.height() - screenCoords.y();

    QVector2D p2d(sx / m_windowSize.width() - 0.5f, sy / m_windowSize.height() - 0.5f);
    //qDebug()< 1? 1 : (x < -1? -1 : x);
}

void TrackballCameraController::createRotation(const QPoint &firstPoint, const QPoint &nextPoint,
                                               QVector3D &dir, float &angle)
{
    auto lastPos3D = projectToTrackball(firstPoint).normalized();
    auto currentPos3D = projectToTrackball(nextPoint).normalized();

    // Compute axis of rotation:
    dir = QVector3D::crossProduct(currentPos3D, lastPos3D);

    // Approximate rotation angle:
    //qDebug()<<"dot:"<rotation();

        auto rotatedAxis = currentRotation.rotatedVector(dir);
        angle *= m_rotationSpeed;

        theCamera->rotateAboutViewCenter(QQuaternion::fromAxisAndAngle(rotatedAxis, angle * M_1_PI * 180));
    }else if(state.middleMouseButtonActive){
        auto offset = m_mouseCurrentPosition - m_mouseLastPosition;
        qDebug()<<"offset:"<translate(QVector3D(-offset.x() / float(m_windowSize.width()) * ls,
                                      offset.y() / float(m_windowSize.height()) * ls,
                                      0));


    }else if(dt != 0){
        qDebug()<<"dt:"<translate(QVector3D(state.txAxisValue * ls,
                                      state.tyAxisValue * ls,
                                      state.tzAxisValue * ls) * dt,
                             Qt3DRender::QCamera::DontTranslateViewCenter);
    }
    m_mouseLastPosition = m_mouseCurrentPosition;
}