After some more searching i have found this old thread:
https://stackoverflow.com/questions/13339963/transparent-qt-widget-and-ogre

Hopefully I can find a way to make the openglContexts work together, which seems to be the problem.

Ill write my solution if i find one! In the meantime if anyone has any other input please let me know!

I think you have to add a QMultiSampleAntiAliasing to either a QRenderStateSet or a QRenderPassFilter. Did you also enable it in the OpenGL format that you set?

@kenchan I knew that.

I want not stacking by z-order, I want simultaneous stacking.

It works something like that by default (if opacity of items is 0.5 )

output = Merge(Merge(background, 0.5 × item1), 0.5 × item2)

I want something like that

output = Merge(background, 0.5 × item1, 0.5 × item2)

aka simultaneous merge items to scene, so it not depends from z-order.
(example — I want ⅓ background, ⅓ item1 and ⅓ item2, Indifferently to items z-order)

@mrjj No, but I will.

I did register but realized I posted with the wrong email address. Now I've corrected it and can see my post on the list. Thank you.

Thanks for sharing !

Hi,

It is a limitation.

http://doc.qt.io/qt-5/qopenglwidget.html

"Limitations
Putting other widgets underneath and making the QOpenGLWidget transparent will not lead to the expected results: The widgets underneath will not be visible. This is because in practice the QOpenGLWidget is drawn before all other regular, non-OpenGL widgets, and so see-through type of solutions are not feasible. Other type of layouts, like having widgets on top of the QOpenGLWidget, will function as expected."

You have to use Qt::WA_AlwaysStackOnTop to do this.

Win7 & Qt 5.4.2 with QtCreator 3.4.1

@SGaist Thanks. I'll give it a look.

@Juaruipav Yes it is activated. Did you try by deactivating it ?
May be it is a bug on Windows 8.1. Better you should report it on Qt Bug Tracker.

@tmason202 , try this one

void QTSemiTransparentWidget::paintEvent(QPaintEvent* event) { QPainter painter(this); painter.setOpacity(0.5); QStyleOption opt; opt.initFrom(this); QStyle* pStyle = QApplication::style(); pStyle->drawPrimitive(QStyle::PE_Widget, &opt, &painter, this); }

at least you should draw something in paint event not to just set an opacity.

Yes of course