[SOLVED]Qt OpenGL - Loading a texture after initialisation

[MrDeathNote]

I've been working with Qt for a while and i'm writing an editor with OpenGL. I've been wondering, do you guys know any way to load a texture after the widget has been initialised? I can't find anything on google. I've been deallocating the widget and creating a new one any time i need to change the texture but this seems like a really inefficient way to do it. Any ideas?

[MrDeathNote]

Since no one replied i assume no one has a solution?

[dandymcgee]

I just spent a few minutes searching and you're right, there doesn't appear to be anything readily available. It seems it shouldn't be too hard, but I haven't played with QT much really. I think I'm going to check it out today, I've wanted to mess with it for a while. I'll let you know if I find anything useful.

[WSPSNIPER]

umm i can load the texture after the widget has been initlized but i cant do it if there are multiple GLWidgets in the scene i just do the old fashion texture loading like you would do with out qt. then i call glBindTexture not window->bindTexture() or window->drawTexture() i do it the old way and it works but ive tried everything to get this window thing working and im getting pissed lol

Code: Select all

QImage temp;
    if(!temp.load(name))
    {
        QFile file("log.txt"); file.open(QIODevice::WriteOnly); file.write("not loaded"); file.close();
    }
    image = QGLWidget::convertToGLFormat(temp);
    glGenTextures(1, &m_texture);

    glBindTexture(GL_TEXTURE_2D, m_texture);

    glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER,GL_NEAREST);
    glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER,GL_NEAREST);

    glTexImage2D(GL_TEXTURE_2D,0,4,image.width(),image.height(),0, GL_RGBA, GL_UNSIGNED_BYTE, image.bits());

that is basically how i do it

[WSPSNIPER]

ok, i fixed the problem i was having and i thought i could pass some of my errors to see if any apply to you. first i did an repaint() on timeout with a QTimer and i never needed to do that because qt takes care of that with out it. then the thing that i think will help you is after you load a texture call updateGL(). because when i started to do this they worked. just some things to try ... im going to post the code so you dont miss

Code: Select all

myLevel.New();
updateGL();

/// creating a new map in the engine loads new textures for the map so when i dident call updateGL it failed but when i called it it worked so if you havent you could give it a try. ill keep looking for you man ;) 

[MrDeathNote]

I've been doin it the old fashioned way myself, i havent been calling updateGL() i'll see if that helps

[WSPSNIPER]

k man i think i found the solution. i ran into the same problem and fixed it with this

Code: Select all

void TileSheet::SetImage(std::string name)
{
    myDir = name.c_str();
    update();
    updateGL();
    repaint();
    myImage->Load(myDir);
}

the tilesheet is a GLWindow derived from QGLWidget and the Image is an Image drived from QImage

ok here is the image load function just in case

Code: Select all

void Image::Load(QString name)
{
    QImage temp;
    if(!temp.load(name))
    {
        QFile file("log.txt"); file.open(QIODevice::WriteOnly); file.write("not loaded"); file.close();
    }
    image = QGLWidget::convertToGLFormat(temp);
    glGenTextures(1, &m_texture);

    glBindTexture(GL_TEXTURE_2D, m_texture);

    glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER,GL_NEAREST);
    glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER,GL_NEAREST);

    glTexImage2D(GL_TEXTURE_2D,0,4,image.width(),image.height(),0, GL_RGBA, GL_UNSIGNED_BYTE, image.bits());

    m_clipRect.setCoords(0, 0, image.width(), image.height());
    m_clipRect.setWidth(image.width());
    m_clipRect.setHeight(image.height());

    m_clipRect.setX(0);
    m_clipRect.setY(0);

    m_position.setCoords(0, 0, image.width(), image.height());
    m_position.setWidth(image.width());
    m_position.setHeight(image.height());
}

[WSPSNIPER]

ok nvm, ive been debugging and i found that all you need to do is call updateGL() before you load anything... if your not in the class of the window call window.updateGL() before loading im happy that i solved this problem

[MrDeathNote]

Thanks man, i had to rearrange it a bit to get it to work but i ended up with:

Code: Select all

void MainWindow::ChangeMap(const char* file)
{
    map->LoadTexture(file);
    update();
    map->updateGL();
    repaint();
}

I had a button set up to test it and with your way i noticed i had to click the button twice for a change. But i've fixed it now, thanks for the help

[WSPSNIPER]

Thanks man, i had to rearrange it a bit to get it to work but i ended up with:

Code: Select all

void MainWindow::ChangeMap(const char* file)
{
    map->LoadTexture(file);
    update();
    map->updateGL();
    repaint();
}

I had a button set up to test it and with your way i noticed i had to click the button twice for a change. But i've fixed it now, thanks for the help

no problem

[MrDeathNote]

Since ive taken another look at it I dont actually need the calls to update() or repaint(), just updateGL().

[WSPSNIPER]

Since ive taken another look at it I dont actually need the calls to update() or repaint(), just updateGL().

ok this is for a previous quote but i now have to click the buttons 2 times to get them to work. how did you fix this?

[MrDeathNote]

Since ive taken another look at it I dont actually need the calls to update() or repaint(), just updateGL().

ok this is for a previous quote but i now have to click the buttons 2 times to get them to work. how did you fix this?

I rearranged the function calls so where you had:

Code: Select all

void TileSheet::SetImage(std::string name)
{
    myDir = name.c_str();
    update();
    updateGL();
    repaint();
    myImage->Load(myDir);
}

I would have:

Code: Select all

void TileSheet::SetImage(std::string name)
{
    myDir = name.c_str();
    myImage->Load(myDir);
    update();
    updateGL();
    repaint();
}

You need to update after you load the texture, updateGL() calls paintGL(). So your new image is rendered.

[WSPSNIPER]

thanks