@DWJO said in Ui doesn't launch when using openGL widgets.: sometimes when debugging, the Ui doesn't launch Please clarify this. only when debugging? I might expect such behaviour in an otherwise correct program being debugged since openGL is its own command processing pipeline. think of it as "parallel processing". So, breakpoints in your Qt program might not consistently apply to what's going on in the GPU pipeline.

@Chris-Kawa That would work for multiple QOpenGLWidgets in the same application. My use case involves sharing the context of one QOpenGLWidget with that of a QOffscreenSurface

@timob256 This is some years old but maybe it helps. Also found this: https://github.com/GarageGames/Qt/blob/master/qt-5/qt3d/src/render/io/objloader.cpp

And this example still has the errors? Then simplify it (and fix the memleaks - a new[] needs a delete[] and paintGL() is not called only once so your vectors grow indefinitly) until we can really try it out. E.g. loading an object file is not needed - drawing a simple rectangle to reproduce the issue is enough.

First try to for the use of OpenGL. Otherwise, you will have to build Qt itself.

One of the issue here is that the conversion must be done each time the draw method is called. If you know that your images will not change or not much then you should do the conversion upfront so that the painting can be optimized.

You should not call GUI function from a different thread. Signal and slots is the way to go.

@SGaist Alright, I'll give that a try. Thanks very much!

@thehans said in QOpenGLWidget::grabFrameBuffer() always ignores alpha channel?: Unfortunately I'm on Ubuntu 18.04 which is still on 5.9.5. Is there any chance of this fix being backported to earlier versions? Qt 5.9 is now in "very strict" update mode, which means in only receives security fixes. It no longer receives bug fixes. Your options are: Download and use Qt 5.12 or newer from https://www.qt.io/download-open-source, OR Apply the patch to your copy of Qt 5.9 and build it from source. I think the first option is easier.

Alright after developing spine problems from leaning into my screen for a week and losing more hair than my GPU has cores, I sort of fixed the issue. So for some reason when I was reading data into my textures without setting the active texture back to the GL_TEXTURE0 default, things were going sideways. So basically I had something like: glActiveTexture(GL_TEXTURE0 + inputTextureUnit[vid]); glBindTexture(GL_TEXTURE_2D, inputTextureID[vid]); glTexImage2D(GL_TEXTURE_2D, 0, GL_internalFormat[vid], videoSpecs[vid].videoWidth, videoSpecs[vid].videoHeight, 0, GL_format[vid], GL_UNSIGNED_BYTE, (const void*)(frame)); But this was missing at the end: glBindTexture(GL_TEXTURE_2D, 0); glActiveTexture(GL_TEXTURE0); But I'm not 100% convinced that this is the cause because if I read still images, there is no issue. Its only when I read videos that I see the flickering and black texture issue. It seems like when other widgets start rendering and there is a texture active, they somehow corrupt it but I would certainly appreciate it if anyone has input on what actually might be happening.

@BoboFuego said in How to use anti-aliasing on QGLWidget?: how can I add MyWidget.h as promoted class for it in the MainWindow constructor? Promoted class won't allow you to pass parameters to a constructor. Just don't add it in the designer at all. Lets say you've got this designer_widget as a central widget of the mian window in the designer. Just delete it entirely and add it in code: MainWindow::Mainwindow(QWidget* parent) : QMainWindow(parent) { ui->setupUi(this); MyWidget* gl_widget = new MyWidget(); setCentralWidget(gl_widget); }

Good ! Then please mark the thread as solved using the "Topic Tools" button so that other forum users may know a solution has worked :)

Hi and welcome to devnet, From the looks of it you are using both glu and the fixed pipeline. Since you are starting a new project, may a suggest taking a look at the Qt OpenGL examples and their use of current technologies like shaders ?

Hi, You should add: Which version of Qt you were using before Which version of Qt you are using now Graphics card + driver Platform you are running on