Problems with Qt OpenGL drawing a textured Quad

[Halcom]

Hallo,

i use Qt 4.7 and want to draw a textured quad, because glDrawPixels is to slow. The texture changed every time i want to redraw, because it cames from a framegrabber.

I Have read some tutorials, the problems is, that he only draw my first image, a gray 256x256 texture. The second one a 512x512 white not. The image buffers and sizes are changed correctly. So i miss something else.

It will be nice if someone could help me.

Here my paintGL method from my QGLWidget. A whole test project is attached.

thanks

void GUIGLView::glInit()
{
 
}
 
void GUIGLView::paintGL()
{
  qglClearColor(QColor(Qt::black));
  glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT | GL_ACCUM_BUFFER_BIT | GL_STENCIL_BUFFER_BIT);
 
  // only do something if image is availible
  if(mImageData.imageBuffer == NULL)
    return;
 
  QString debugString = QString("paintGL called with buffer: 0x%1, size %2").arg((int)mImageData.imageBuffer,8,16,QChar('0')).arg(mImageData.width);
  qDebug(debugString.toAscii().data());
 
  // set projection - disable z-axis
  glMatrixMode(GL_PROJECTION);
 
  //clear projection matrix
  glLoadIdentity();
 
  //Creating an orthoscopic view matrix going from -1 -> 1 in each
  //dimension on the screen (x, y, z).
  glOrtho(0, 640, 480, 0, -1, 1);
 
  //Now editing the model-view matrix.
  glMatrixMode(GL_MODELVIEW);
 
  //Clearing the model-view matrix.
  glLoadIdentity();
 
  //Disabling the depth test (z will not be used to tell what object
  //will be shown above another, only the order in which I draw them.)
  glDisable(GL_DEPTH_TEST);
 
  // generate a texture
  glGenTextures(1, &mTextureID);
 
  // enable texturing
  glEnable(GL_TEXTURE_2D);
 
  //specify texture to use
  glBindTexture(GL_TEXTURE_2D, mTextureID);
 
  // set texturing parameters
  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
 
  // copy image to texture
  glTexImage2D(GL_TEXTURE_2D, 0, mImageData.samplesPerPixel, mImageData.width, mImageData.height, 0, GL_RGB, GL_UNSIGNED_BYTE, mImageData.imageBuffer);
 
  // draw a textured quad
  glBegin(GL_QUADS);
    glTexCoord2f(0,0); glVertex3f(  0,   0,0); //lo
    glTexCoord2f(0,1); glVertex3f(256,   0,0); //lu
    glTexCoord2f(1,1); glVertex3f(256, 256,0); //ru
    glTexCoord2f(1,0); glVertex3f(  0, 256,0); //ro
  glEnd;
 
  glDeleteTextures(1, &mTextureID);
  mTextureID = 0;
}

void GUIGLView::glInit()
{

}

void GUIGLView::paintGL()
{
  qglClearColor(QColor(Qt::black));
  glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT | GL_ACCUM_BUFFER_BIT | GL_STENCIL_BUFFER_BIT);

  // only do something if image is availible
  if(mImageData.imageBuffer == NULL)
    return;

  QString debugString = QString("paintGL called with buffer: 0x%1, size %2").arg((int)mImageData.imageBuffer,8,16,QChar('0')).arg(mImageData.width);
  qDebug(debugString.toAscii().data());

  // set projection - disable z-axis
  glMatrixMode(GL_PROJECTION);

  //clear projection matrix
  glLoadIdentity();

  //Creating an orthoscopic view matrix going from -1 -> 1 in each
  //dimension on the screen (x, y, z).
  glOrtho(0, 640, 480, 0, -1, 1);

  //Now editing the model-view matrix.
  glMatrixMode(GL_MODELVIEW);

  //Clearing the model-view matrix.
  glLoadIdentity();

  //Disabling the depth test (z will not be used to tell what object
  //will be shown above another, only the order in which I draw them.)
  glDisable(GL_DEPTH_TEST);

  // generate a texture
  glGenTextures(1, &mTextureID);

  // enable texturing
  glEnable(GL_TEXTURE_2D);

  //specify texture to use
  glBindTexture(GL_TEXTURE_2D, mTextureID);

  // set texturing parameters
  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);

  // copy image to texture
  glTexImage2D(GL_TEXTURE_2D, 0, mImageData.samplesPerPixel, mImageData.width, mImageData.height, 0, GL_RGB, GL_UNSIGNED_BYTE, mImageData.imageBuffer);

  // draw a textured quad
  glBegin(GL_QUADS);
    glTexCoord2f(0,0); glVertex3f(  0,   0,0); //lo
    glTexCoord2f(0,1); glVertex3f(256,   0,0); //lu
    glTexCoord2f(1,1); glVertex3f(256, 256,0); //ru
    glTexCoord2f(1,0); glVertex3f(  0, 256,0); //ro
  glEnd;

  glDeleteTextures(1, &mTextureID);
  mTextureID = 0;
}

To copy to clipboard, switch view to plain text mode 

[Halcom]

One Problems solved, missing () behind glEnd(). Sometimes i hate compilers.

But the screen is not correctly cleared.