[Interest] Setting current QOpenGLContext with an EGLContext

[Thomas Sevaldrud]

Ok, I can live with the dummy offscreen surface, it seems to work OK at
least.

I have now tried to create a multisample FBO for blitting into the PBuffer,
but it's not entirely straight forward it seems :-) What I've done is this:


    QOpenGLFramebufferObjectFormat format;

    format.setAttachment(QOpenGLFramebufferObject::CombinedDepthStencil);

    format.setSamples(4);

    gl_fbo_ = new QOpenGLFramebufferObject(fbo_size, format);


    ...


    gl_fbo_->bind();


    .. render stuff...


    gl_fbo_->release();

    QImage img(gl_fbo_->toImage()); // For debugging

    img.save("fbo_test.png");

    gl_context_->makeCurrent(gl_dummy_surface_);

    eglMakeCurrent(egl_display_, egl_pbuffer_, egl_pbuffer_, egl_context_);

    QOpenGLFramebufferObject::blitFramebuffer(NULL, gl_fbo_);


The "fbo_test.png" image contains the OpenGL scene as it should, but the
PBuffer remains black. Any ideas?

- Thomas


On Tue, Sep 29, 2015 at 4:30 PM, Agocs Laszlo <laszlo.agocs at theqtcompany.com
> wrote:

> Well, there’s no nice solution since QOffscreenSurface is backed by a
> window, not a pbuffer on Windows. (arguably this should be changed in some
> future release, for ANGLE at least, but that won’t help you now)
>
>
>
> You can make a QOpenGLContext current with a QOffscreenSurface, then call
> eglMakeCurrent directly with the pbuffer surface and the  EGLContext you
> dig out from the QOpenGLContext. This way Qt’s tracking will be correct
> (when it comes to the current QOpenGLContext) too.
>
>
>
> This is apparently exactly what you are doing already.
>
>
>
> As for the multisample issues, it could be that multisampling is not
> supported for pbuffers. As a workaround you could render into an FBO with a
> multisample renderbuffer (assuming that’s supported) and then blit that
> into the default framebuffer (FBO 0) of the pbuffer surface.
>
>
>
> BR,
>
> Laszlo
>
> *From:* interest-bounces+laszlo.agocs=theqtcompany.com at qt-project.org
> [mailto:interest-bounces+laszlo.agocs=theqtcompany.com at qt-project.org] *On
> Behalf Of *Thomas Sevaldrud
> *Sent:* 29. september 2015 15:24
> *To:* Interest at qt-project.org
> *Subject:* Re: [Interest] Setting current QOpenGLContext with an
> EGLContext
>
>
>
> It works if I add a dummy OffscreenSurface and make my context current on
> this before making the PBuffer current. Not sure if this is the best way of
> doing it though?
>
>
>
> - Thomas
>
>
>
> On Tue, Sep 29, 2015 at 11:37 AM, Thomas Sevaldrud <thomas at silentwings.no>
> wrote:
>
> Hi,
>
>
>
> I'm still working on the EGL PBuffer/DirectX integration through Qt that I
> posted about last week :-)
>
>
>
> Thanks to good help from this list I now have the PBuffer and DirectX
> texture set up with the share handle. I also have a QOpenGLContext which I
> have used to set up the EGL PBuffer. I don't have a QSurface though, since
> my surface is the EGL PBuffer.
>
>
>
> So, the question now is how do I make the QOpenGLContext current. (I need
> a QOpenGLContext::currentContext() for QOpenGLFunctions and so on).
>
>
>
> The code looks something like this:
>
>
>
>     glContext_ = new QOpenGLContext;
>
>     glContext_->setFormat(format);
>
>     glContext_->create();
>
>
>
>     ....
>
>
>
>     QPlatformNativeInterface *nativeInterface = QGuiApplication::platformNativeInterface();
>
>     egl_display_ = static_cast<EGLDisplay>(nativeInterface->*nativeResourceForContext*("eglDisplay", glContext_));
>
>     egl_context_ = static_cast<EGLContext>(nativeInterface->*nativeResourceForContext*("eglContext", glContext_));
>
>     EGLConfig egl_config = static_cast<EGLConfig>(nativeInterface->*nativeResourceForContext*("eglConfig", glContext_));
>
>
>
>     EGLint attribs[] = { ...
>
>
>
>     };
>
>
>
>     egl_pbuffer_ = eglCreatePbufferSurface(egl_display_, egl_config, attribs);
>
>
>
>     ... D3D setup stuff...
>
>
>
>     // Start rendering to PBuffer:
>
>
>
>     eglMakeCurrent(egl_display_, egl_pbuffer_, egl_pbuffer_, egl_context_);
>
>
>
>     ... Here I should like to set glContext current somehow...
>
>
>
> Any ideas?
>
>
>
> - Thomas
>
>
>
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