Lazslo, Thank you very much for your prompt reply.
If I will be doing this very very regularly, should I keep an instance of the FBO instance of creating and deleting all the time? Best regards, Nuno > On 15 May 2024, at 15:46, Laszlo Agocs <laszlo.ag...@qt.io> wrote: > > > Hi Nuno, > > You can always create an FBO on the fly for the purposes of the readback. > > For example, something along the lines of: > > glGenFramebuffers(1, &fbo); > glBindFramebuffer(GL_FRAMEBUFFER, fbo); > glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, > texture, 0); > glReadPixels(...); > glBindFramebuffer(GL_FRAMEBUFFER, context->defaultFramebufferObject()); > glDeleteFramebuffers(1, &fbo); > > Best regards, > Laszlo > > From: Nuno Santos <nuno.san...@imaginando.pt > <mailto:nuno.san...@imaginando.pt>> > Sent: Wednesday, May 15, 2024 4:29 PM > To: Laszlo Agocs <laszlo.ag...@qt.io <mailto:laszlo.ag...@qt.io>> > Cc: interestqt-project. org <interest@qt-project.org > <mailto:interest@qt-project.org>> > Subject: Re: [Interest] Porting Qt5 OpenGL app to Qt6 - QQuickRenderTarget > and OpenGL frame buffer object > > Laszlo, > > I have a new problem regarding this question. > > I have a QQuickRenderControl in order to do a side render and be able to > extract the render output. I was reading from the FBO using the glReadPixels > function. > > But now the render target is a OpenGL Texture but apparently the function > that reads from a GLTexture is glGetTexImage but that function is not on the > qopenglfunctions. > > How can I read the texture now? > > Thanks! > > Best regards, > > Nuno > >> On 8 May 2024, at 16:41, Laszlo Agocs <laszlo.ag...@qt.io >> <mailto:laszlo.ag...@qt.io>> wrote: >> >> Hi, >> >> Passing 0 as a renderbuffer object name is not going to work. Try using >> https://doc.qt.io/qt-6/qquickrendertarget.html#fromOpenGLTexture with the >> texture that is used as the color attachment of your OpenGL framebuffer >> object. (actually that FBO is not useful in Qt 6 as one will be created >> internally as needed) >> >> Best regards, >> Laszlo >> >> From: Interest <interest-boun...@qt-project.org >> <mailto:interest-boun...@qt-project.org>> on behalf of Nuno Santos via >> Interest <interest@qt-project.org <mailto:interest@qt-project.org>> >> Sent: Tuesday, April 16, 2024 4:21 PM >> To: interestqt-project. org <interest@qt-project.org >> <mailto:interest@qt-project.org>> >> Subject: [Interest] Porting Qt5 OpenGL app to Qt6 - QQuickRenderTarget and >> OpenGL frame buffer object >> >> Hi, >> >> I have an application that was heavily written on top of OpenGL. Right now I >> want to port it to Qt 6 with the minimum effort trying to stick to the >> OpenGL backend until I get the grip on the new things of Qt 6 Graphics API >> abstraction. >> >> I used to do this in order to assign a target FBO to a QuickWindow: >> >> _quickWindow->setRenderTarget(_fboRender); >> >> This is no longer possible and it requires a QQuickRenderTarget to be >> created and I seem to have three options: >> >> (since 6.2) QQuickRenderTarget fromOpenGLRenderBuffer(uint renderbufferId, >> const QSize &pixelSize, int sampleCount = 1) >> (since 6.4) QQuickRenderTarget fromOpenGLTexture(uint textureId, uint >> format, const QSize &pixelSize, int sampleCount = 1) >> QQuickRenderTarget fromOpenGLTexture(uint textureId, const QSize >> &pixelSize, int sampleCount = 1) >> >> I’m trying this: >> >> _renderTarget = QQuickRenderTarget::fromOpenGLRenderBuffer(0, >> QSize(_renderResolution.width(), _renderResolution.height())); >> _quickWindow->setRenderTarget(_renderTarget); >> >> But nothing appears on the screen and I get a warning: >> >> QQuickWindow: No render target (neither swapchain nor custom target was >> provided) >> >> Can anyone tell me what am I failing here? >> >> Any ideas suggestions are very welcome. >> >> With my best regards, >> >> Nuno >> _______________________________________________ >> Interest mailing list >> Interest@qt-project.org <mailto:Interest@qt-project.org> >> https://lists.qt-project.org/listinfo/interest
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