Skip to content
  • Categories
  • Recent
  • Tags
  • Popular
  • Users
  • Groups
  • Search
  • Get Qt Extensions
  • Unsolved
Collapse
Brand Logo
  1. Home
  2. Qt Development
  3. General and Desktop
  4. PaintGL() doesn't work
Forum Updated to NodeBB v4.3 + New Features

PaintGL() doesn't work

Scheduled Pinned Locked Moved General and Desktop
4 Posts 2 Posters 1.8k Views 1 Watching
  • Oldest to Newest
  • Newest to Oldest
  • Most Votes
Reply
  • Reply as topic
Log in to reply
This topic has been deleted. Only users with topic management privileges can see it.
  • B Offline
    B Offline
    bear234
    wrote on last edited by
    #1

    i want to run opengl in Qt and i used QGLWidget to do this but it doesn't work.

    here is my code:
    @
    #include <QGLWidget>

    class GLWidget : public QGLWidget
    {
    Q_OBJECT
    public:
    explicit GLWidget(QWidget *parent = 0);

    virtual void initializeGL();
    virtual void resizeGL(int w, int h);
    virtual void paintGL();
    

    };
    @

    @
    #include "glwidget.h"
    #include <gl/glut.h>

    GLWidget::GLWidget(QWidget *parent) :
    QGLWidget(parent)
    {}

    void GLWidget::initializeGL()
    {
    setGeometry(300, 150, 640, 480);
    glShadeModel(GL_FLAT);
    glClearColor(0.5, 1.0, 0.2, 0);
    glClearDepth(1.0);
    glEnable(GL_DEPTH_TEST);
    glDepthFunc(GL_LEQUAL);
    glHint(GL_PERSPECTIVE_CORRECTION_HINT, GL_NICEST);
    }

    void GLWidget::resizeGL(int w, int h)
    {
    if(0 == h)
    h = 1;
    glViewport(0, 0, (GLint)w, (GLint)h);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    // gluPerspective(45.0, (GLfloat)width/(GLfloat)height, 0.1, 100.0);
    //glMatirxMode(GL_MODELVIEW);
    glLoadIdentity();
    }

    void GLWidget::paintGL()
    {
    //qglClearColor(QColor(0,0,255,128));
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();
    glColor3f(0.0, 0.0, 1.0);
    glBegin(GL_TRIANGLES);
    glVertex3f(0.0,1.0,0.0);
    glVertex3f(-1.0,-1.0,0.0);
    glVertex3f(1.0,-1.0,0.0);
    glEnd();
    }
    @

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

    GLWidget *gl = new GLWidget();
    gl->updateGL();
    gl->show();
    
    return a.exec&#40;&#41;;
    

    }
    @

    it seems that the fonction initializeGL works because the color of background changes. but i cant see my triangle.
    could someone help me plz???

    1 Reply Last reply
    0
    • B Offline
      B Offline
      bear234
      wrote on last edited by
      #2

      by the way, the version of my qt is 5.0.2

      1 Reply Last reply
      0
      • Chris KawaC Offline
        Chris KawaC Offline
        Chris Kawa
        Lifetime Qt Champion
        wrote on last edited by
        #3

        The background color is set by the glClear() call, not glClearColor(), so your paintGL() does work.

        Btw. "doesn't work" is not very descriptive.

        You didn't set a proper transformation matrix and you draw at depth 0.0 so your triangle falls outside of the view frustum.

        For drawing a flat 2D triangle you can try this:
        @
        void GLWidget::resizeGL(int w, int h) {
        glViewport(0, 0, w, h);
        glMatrixMode(GL_PROJECTION);
        glLoadIdentity();
        glOrtho(-1, 1, -1, 1, -1, 1);
        glMatrixMode(GL_MODELVIEW);
        glLoadIdentity();
        }

        void GLWidget::paintGL() {
        glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
        glColor3f(0.0, 0.0, 1.0);
        glBegin(GL_TRIANGLES);
        glVertex2f(0.0,1.0);
        glVertex2f(-1.0,-1.0);
        glVertex2f(1.0,-1.0);
        glEnd();
        }
        @

        1 Reply Last reply
        0
        • B Offline
          B Offline
          bear234
          wrote on last edited by
          #4

          thx. i copied ur two functions.
          but i cant still see the triangle...

          [quote author="Chris Kawa" date="1417448239"]The background color is set by the glClear() call, not glClearColor(), so your paintGL() does work.

          Btw. "doesn't work" is not very descriptive.

          You didn't set a proper transformation matrix and you draw at depth 0.0 so your triangle falls outside of the view frustum.

          For drawing a flat 2D triangle you can try this:
          @
          void GLWidget::resizeGL(int w, int h) {
          glViewport(0, 0, w, h);
          glMatrixMode(GL_PROJECTION);
          glLoadIdentity();
          glOrtho(-1, 1, -1, 1, -1, 1);
          glMatrixMode(GL_MODELVIEW);
          glLoadIdentity();
          }

          void GLWidget::paintGL() {
          glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
          glColor3f(0.0, 0.0, 1.0);
          glBegin(GL_TRIANGLES);
          glVertex2f(0.0,1.0);
          glVertex2f(-1.0,-1.0);
          glVertex2f(1.0,-1.0);
          glEnd();
          }
          @[/quote]

          1 Reply Last reply
          0

          • Login

          • Login or register to search.
          • First post
            Last post
          0
          • Categories
          • Recent
          • Tags
          • Popular
          • Users
          • Groups
          • Search
          • Get Qt Extensions
          • Unsolved