How to improve memory-consumption when drawing polygons, (poly-)lines and points

I'm currently struggling with populating a qgraphicsscene with many (> 1Million) objects (Polygons, Lines, Points). What I've observed is, that when creating randomly 100000 Polygons, I'm already ending up withe 130MB memory consumption. (The simple example below is based on a default Qt-Project using the View.cpp of the chip-demo example)

Code:

QtGrafikTestBasic::QtGrafikTestBasic(QWidget *parent): QMainWindow(parent)
    {
        ui.setupUi(this);
        QSplitter *h1Splitter = new QSplitter;
        QSplitter *vSplitter = new QSplitter;
        vSplitter->addWidget(h1Splitter);
 
        View* view = new View("asdf");
        h1Splitter->addWidget(view);
 
        QHBoxLayout *layout = new QHBoxLayout;
        layout->addWidget(vSplitter);
        setLayout(layout);
        setCentralWidget(view);
 
        QBrush *brush = new QBrush();
        brush->setColor(Qt::blue);
        brush->setStyle(Qt::SolidPattern);
        QPen *pen = new QPen();
        pen->setWidth(0);
 
        QGraphicsScene *scene = new QGraphicsScene;
        srand ( time(NULL) );
        int m_PolyWidth = 10;
 
        for (int i = 0 ; i < 100000; i++)
        {
            double lBaseX = rand() % ((int)floor(width())  - m_PolyWidth);
            double lBaseY = rand() % ((int)floor(height()) - m_PolyWidth);
 
            QPolygonF polygon;
            polygon << QPointF(lBaseX, lBaseY);
            polygon << QPointF(lBaseX + m_PolyWidth, lBaseY);
            polygon << QPointF(lBaseX + m_PolyWidth, lBaseY + m_PolyWidth);
            polygon << QPointF(lBaseX, lBaseY + m_PolyWidth);
 
            scene->addPolygon(polygon, *pen, *brush);
        }
        view->view()->setScene(scene);
     }

So what am I doint wrong here / where can I improve? I've read some posts of creating an own class like the chip-example, so I simply used the chip example but also there I've encountered the problem that as soon as I change the part which uniformly distributes the chips from

Code:

item->setPos(QPointF(i, j));

to a random distribution

Code:

item->setPos(QPointF(lBaseX, lBaseY));

, the memory consumption explodes also here...

So, what is the most performant and least memory-consuming way of drawing polygons, (poly-)lines and points in Qt?