How to draw with vertices, circle (and other shapes) ?

timob256

I drew a circle.
But for some reason he is twitchy, as if he was drawn by a man without a dividers.
I think this is because drawPoint takes an int. And I have a float vector .

here is all the code :

**krug_gt.h**

#ifndef KRUG_QT_H
#define KRUG_QT_H

#include <QMainWindow>
#include <QDebug>
#include <QPainter>
#include <QPen>
#include <QFont>
#include <QtMath>


class Krug_qt : public QMainWindow
{
    Q_OBJECT

public:
    Krug_qt(QWidget *parent = 0);
    ~Krug_qt();

    void fillVertexArray();

    float R;        // радиус
    int p;          // Количество продольных срезов. Number of longitudinal slices.
    int q;          // Количество широтных срезов. Number of latitudinal slices.
    int kol_toch;

    QVector<float> integerVector;


protected:
    void paintEvent(QPaintEvent *event);
//     void keyPressEvent(QKeyEvent *event);
};

#endif // KRUG_QT_H

kruq_qt.cpp

#include "krug_qt.h"

Krug_qt::Krug_qt(QWidget *parent)
    : QMainWindow(parent)
{
    R = 90.0;
    q = 24;
    p = 24;

    kol_toch = 180;
}

Krug_qt::~Krug_qt()
{

}

void Krug_qt::fillVertexArray()
{
    float grad = 360.0/kol_toch;
    float grad_kol_toch = 0.0;
    // градусы*M_PI/180 = радианы
    int j;
    for (j = 0; j <= kol_toch; ++j){
        integerVector.append(R * cos(grad_kol_toch*M_PI/180));
        integerVector.append(R * sin(grad_kol_toch*M_PI/180));
        grad_kol_toch = grad_kol_toch + grad;
    }
}

void Krug_qt::paintEvent(QPaintEvent *event)
{
    integerVector.clear();
    QPainter painter(this);                                   // Создаём объект отрисовщика
    QPen pen_abris(Qt::black, 2, Qt::SolidLine, Qt::FlatCap); // кисть обрисовки (компаса)
    painter.setRenderHint(QPainter::Antialiasing);            // убираем резкие кубики
    painter.setPen(pen_abris);                                // Устанавливаем кисть обрисовки
    fillVertexArray();                                        // Набираем массив
    painter.translate(this->width()/2, this->height()/2);     // смещение отрисовки

    qDebug() << integerVector.size();

    for(int i =0; i<integerVector.size(); i++)
    {
        painter.drawPoint(integerVector[i],integerVector[i++]);
        i++;
    }
}

main.cpp

#include "krug_qt.h"
#include <QApplication>

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    Krug_qt w;
    w.show();

    return a.exec();
}

timob256

#include "krug_qt.h"

Krug_qt::Krug_qt(QWidget *parent)
: QMainWindow(parent)
{
R = 90.0;
q = 24;
p = 24;

kol_toch = 180;

}

Krug_qt::~Krug_qt()
{

}

void Krug_qt::fillVertexArray()
{
float grad = 360.0/kol_toch;
float grad_kol_toch = 0.0;
// градусыM_PI/180 = радианы
int j;
for (j = 0; j <= kol_toch; ++j){
integerVector.append(R * cos(grad_kol_tochM_PI/180.0));
integerVector.append(R * sin(grad_kol_toch*M_PI/180.0));
grad_kol_toch = grad_kol_toch + grad;
}
}

void Krug_qt::paintEvent(QPaintEvent *event)
{
integerVector.clear();
QPainter painter(this); // Создаём объект отрисовщика
QPen pen_abris(Qt::black, 2, Qt::SolidLine, Qt::FlatCap); // кисть обрисовки (компаса)
painter.setRenderHint(QPainter::Antialiasing); // убираем резкие кубики
painter.setPen(pen_abris); // Устанавливаем кисть обрисовки
fillVertexArray(); // Набираем массив
painter.translate(this->width()/2, this->height()/2); // смещение отрисовки

qDebug() << integerVector.size();

int f = 0;
for(int i =0; i<integerVector.size()/2; i++)
{
    i++; f++;
    painter.drawPoint(QPointF(integerVector[--i],integerVector[i]));
    qDebug() << "f :"<<f;

// painter.drawPoint(QPointF(integerVector[i],integerVector[i++]));
// i++;
}
}

mrjj

Hi

yes I also think its due to INT cutting.

you could use
https://doc.qt.io/qt-5.15/qpainter.html#drawPoint

and QPointF instead and also change your list to use that type.

timob256

----and QPointF instead and also change your list to use that type.

I do not know how to do this

mrjj

@timob256

Hi
just change the type for the definition "integerVector"

I assume you have something like
std::vector<int > integerVector;
and change into
std::vector<QPointF> integerVector;

and for the
integerVector.append
will just be using a QPointF instead.

ah missed it.
QVector<float> integerVector;
so that will be
QVector<QPointF> integerVector;

and maybe not call it integer vector but points or something like that ? :)

timob256