QGLWidget won't display anything except the clear color

[alexbcd]

Hello,

I have started to develop a 3D viewer on a computer, and I would like to test it on another one. Both of them are under ubuntu lucid lynx. Unfortunately, on the second computer, the QGLWidget is blank. I have made up a minimal application that doesn't work neither on that second computer :

#ifndef GLVIEWER_H
#define GLVIEWER_H
#include <QtOpenGL/qgl.h>
 
class GLViewer : public QGLWidget {
 
public:
  GLViewer(QWidget * parent = 0);
  ~GLViewer();
 
protected:
  int viewport[4];
 
  void initializeGL();
  void resizeGL (int width, int height);
  void paintGL();
 
 
};
 
#endif // GLVIEWER_H

#ifndef GLVIEWER_H
#define GLVIEWER_H
#include <QtOpenGL/qgl.h>

class GLViewer : public QGLWidget {

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

protected:
  int viewport[4];

  void initializeGL();
  void resizeGL (int width, int height);
  void paintGL();


};

#endif // GLVIEWER_H

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and

#include "GLViewer.h"
 
GLViewer::GLViewer(QWidget * parent)
  : QGLWidget(parent)
{
 
}
 
GLViewer::~GLViewer() {
 
}
 
void GLViewer::initializeGL() {
 
}
 
void GLViewer::resizeGL(int width, int height) {
  viewport[0] = 0;
  viewport[1] = 0;
  viewport[2] = width;
  viewport[3] = height;
  glViewport(0, 0, width, height);
}
 
void GLViewer::paintGL() {
  glClearColor(1,1,1,1);
  glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
  glMatrixMode(GL_PROJECTION);
  glLoadIdentity();
  glOrtho(-1.0, 1.0, -1.0, 1.0, 0, 1);
  glMatrixMode(GL_MODELVIEW);
  glLoadIdentity();
  glColor3f(0.0f, 0.0f, 1.0f);
  glBegin(GL_TRIANGLES);
  glVertex3f(0,0,.5);
  glVertex3f(0,1,.5);
  glVertex3f(1,1,.5);
  glEnd();
}

#include "GLViewer.h"

GLViewer::GLViewer(QWidget * parent)
  : QGLWidget(parent)
{

}

GLViewer::~GLViewer() {

}

void GLViewer::initializeGL() {

}

void GLViewer::resizeGL(int width, int height) {
  viewport[0] = 0;
  viewport[1] = 0;
  viewport[2] = width;
  viewport[3] = height;
  glViewport(0, 0, width, height);
}

void GLViewer::paintGL() {
  glClearColor(1,1,1,1);
  glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
  glMatrixMode(GL_PROJECTION);
  glLoadIdentity();
  glOrtho(-1.0, 1.0, -1.0, 1.0, 0, 1);
  glMatrixMode(GL_MODELVIEW);
  glLoadIdentity();
  glColor3f(0.0f, 0.0f, 1.0f);
  glBegin(GL_TRIANGLES);
  glVertex3f(0,0,.5);
  glVertex3f(0,1,.5);
  glVertex3f(1,1,.5);
  glEnd();
}

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What it does is to draw a blank area in clearColor, but nothing else. It seems however that the Qt precompiled demo are working well with opengl. Where can the problem come from ?

[manmohan]

you have to organise your code ...you have to go along in this way. this is just an example you can place your own opengl drawing code in paintGL() function
[QTCODE]
void GLWidget::initializeGL()
{
qglClearColor(Qt::gray);
glShadeModel(GL_SMOOTH);
}
void GLWidget::resizeGL(int width, int height)
{
glViewport(0, 0, width, height);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
GLfloat x = GLfloat(width) / height;
glFrustum(-x, +x, -1.0, +1.0, 4.0, 20.0);
glMatrixMode(GL_MODELVIEW); }

void GLWidget:aintGL()
{ glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
glTranslatef(0.0, 0.0, -15.0);
glRotatef(rotationX, 1.0, 0.0, 0.0);
glRotatef(rotationY, 0.0, 1.0, 0.0);
glRotatef(rotationZ, 0.0, 0.0, 1.0);
pobj = gluNewQuadric();
gluQuadricDrawStyle(pobj, GLU_LINE);
gluQuadricNormals(pobj, GLU_SMOOTH);
qglColor(Qt::red);
gluCylinder(pobj, 1, 1, 3, 30, 30); }
[/QTCODE]