记一次QT 2D 画图 实现3D动态效果

最近在学习古老的QT开发手册，其中有一节是使用QT画图来实现正弦函数的小demo,稍微改变了一点，结果实现的结果超出了预期的想象，实现了3D的效果特此记录

//头文件
class drawDemo : public QWidget
{
    Q_OBJECT

public:
    explicit drawDemo(QWidget *parent = nullptr);
    ~drawDemo();
public slots:
    void flushBuff();
protected:
    virtual void paintEvent(QPaintEvent *);

private:
    int buffer[200];
    QTimer * timer;
    const double PI = 3.1415926;

    Ui::drawDemo *ui;
};

#endif // DRAWDEMO_H

//cpp
drawDemo::drawDemo(QWidget *parent) :
    QWidget(parent),
    ui(new Ui::drawDemo)
{
    ui->setupUi(this);

    this->setWindowTitle("test");

    this->setStyleSheet("QWidget{background:#000000;}");
    this->setGeometry(QRect(40,40,402,252));

    for(int i = 0;i<200;i++)
    {
        buffer[i] = static_cast<int>((sin((i*PI)/100)*100));

    }

    timer = new QTimer();
    connect(timer,&QTimer::timeout,this,&drawDemo::flushBuff);

    timer->start(30);

}

drawDemo::~drawDemo()
{
    delete ui;
}

void drawDemo::flushBuff()
{
    int temp = buffer[0];

    for(int i = 0;i<200;i++)
    {
        buffer[i]=buffer[i+1];
    }
    buffer[199]=temp;
    update();
}

void drawDemo::paintEvent(QPaintEvent *)
{

    QPainter painter(this);
    QPoint beginPoint;
    QPoint endPoint;
    painter.setPen(Qt::blue);
    for(int i = 0;i<199;i++)
    {
        beginPoint.setX(2*i);
        beginPoint.setY(buffer[i]+125);
        endPoint.setX(2*i+i);
        endPoint.setY(buffer[i+1]+125);
        painter.drawLine(beginPoint,endPoint);
    }

}

实现结果: