[Interest] Qt3D - Render to QImage

[Sean Harmer]

On Monday 28 November 2016 11:48:14 Harald Vistnes wrote:
> Hi,
> 
> yes, this would be a most welcome feature.
> 
> Concerning Jira, it has already been requested multiple times
> https://bugreports.qt.io/browse/QTBUG-52074
> https://bugreports.qt.io/browse/QTBUG-52136

I meant for reading back from a buffer. :)

> I tried to render into a FBO and read back the results, but had some
> problems. I attached some test code in the Jira
> https://bugreports.qt.io/secure/attachment/57353/offscreenrenderer.zip but
> never got any feedback. If someone will look into this it would be great.

I'll see if someone can take a look. I may have some time next week if nobody 
else can.

Cheers,

Sean

> 
> Thanks,
> Harald
> 
> 2016-11-28 11:41 GMT+01:00 Sean Harmer <sean.harmer at kdab.com>:
> > On Monday 28 November 2016 11:40:10 Juan Jose Casafranca wrote:
> > > Oh thanks!
> > > 
> > > Yes, in fact my first thought was to use it for a compute shader. It
> > 
> > would
> > 
> > > make Qt3D a great tool not only for rendering but also for GPGPU.
> > > I will try to have a look on it during the Christmas vacations :-)
> > 
> > Awesome! Drop by #qt-3d on irc if you need anything.
> > 
> > Cheers,
> > 
> > Sean
> > 
> > > 2016-11-28 11:31 GMT+01:00 Sean Harmer <sean.harmer at kdab.com>:
> > > > Hi,
> > > > 
> > > > On Monday 28 November 2016 11:22:30 Juan Jose Casafranca wrote:
> > > > > Hi Sean,
> > > > > 
> > > > > is there any example on how to do that? I tried to use a
> > 
> > QRenderCapture
> > 
> > > > but
> > > > 
> > > > > I failed two weeks ago.
> > > > 
> > > > http://code.qt.io/cgit/qt/qt3d.git/tree/tests/manual/rendercapture-qml
> > > > http://code.qt.io/cgit/qt/qt3d.git/tree/tests/manual/rendercapture-cpp
> > > > 
> > > > > Is there any way to access the buffers content data using a similar
> > > > > approach to the QRenderCapture method?
> > > > > For example, in an animation system, use a graphics pipeline to
> > 
> > compute
> > 
> > > > the
> > > > 
> > > > > deformed mesh and then get the new vertex positions for export.
> > > > 
> > > > Right, that is missing at the moment. It would be very useful to be
> > 
> > able
> > 
> > > > to do
> > > > this to read back the results of a compute shader too for e.g.. If you
> > > > wish to
> > > > have a go at adding such a feature analogous the the RenderCapture
> > > > node
> > > > then
> > > > that would be awesome. If not, we can try to do it for 5.9 but the
> > 
> > feature
> > 
> > > > freeze is approaching. In either case could you file a JIRA for it
> > 
> > please?
> > 
> > > > Thanks!
> > > > 
> > > > Sean
> > > > 
> > > > > Cheers
> > > > > Juan José
> > > > > 
> > > > > 2016-11-28 11:13 GMT+01:00 Sean Harmer <sean.harmer at kdab.com>:
> > > > > > On Monday 28 November 2016 02:23:59 Philip Schuchardt wrote:
> > > > > > > I'm trying to port my OpenGL code (https://github.com/Cavewhere/
> > > > > > 
> > > > > > cavewhere/)
> > > > > > 
> > > > > > > to use Qt3D. I think Qt3D will allow me to quickly improve and
> > > > 
> > > > modify my
> > > > 
> > > > > > > rendering pipeline. The one requirement I need is to be able to
> > > > 
> > > > render
> > > > 
> > > > > > to a
> > > > > > 
> > > > > > > QImage and save it to disk. Currently, have a method that
> > > > > > > renders
> > > > > > > high-resolution images from OpenGL. I do this by tiling a
> > 
> > projection
> > 
> > > > > > matrix
> > > > > > 
> > > > > > > and rendering the scene one tile at a time and combining them
> > 
> > into
> > 
> > > > > > > on
> > > > > > 
> > > > > > huge
> > > > > > 
> > > > > > > PNG. The problem is I'm not sure how to render Qt3D pipeline to
> > > > > > > a
> > > > > > > texture
> > > > > > > and then download if from the GPU into memory in Qt3D. Is there
> > 
> > an
> > 
> > > > easy
> > > > 
> > > > > > way
> > > > > > 
> > > > > > > to do that? Do I need to create my own Aspect?
> > > > > > 
> > > > > > Hi, you can use a custom frame graph that includes a
> > > > > > QRenderCapture
> > > > 
> > > > node
> > > > 
> > > > > > (coming in Qt 5.8). If you combine this with a camera and some
> > 
> > logic
> > 
> > > > for
> > > > 
> > > > > > tiling the frustum (NodeInstantiator) you should be able to
> > 
> > replicate
> > 
> > > > your
> > > > 
> > > > > > existing logic. I'd like to get something like this wrapped up
> > 
> > along
> > 
> > > > with
> > > > 
> > > > > > Qt
> > > > > > 5.9.
> > > > > > 
> > > > > > > Also, many parts of the documentation seem to be missing, very
> > > > > > > light,
> > > > > > > and
> > > > > > > not up to the same standard as the rest of Qt's documentation.
> > > > > > 
> > > > > > Yes this is something I really want to have a push on in the near
> > > > 
> > > > future.
> > > > 
> > > > > > Cheers,
> > > > > > 
> > > > > > Sean
> > > > > > 
> > > > > > > Perhaps,
> > > > > > > I'm just missing something from the undocumented documentation.
> > > > > > > 
> > > > > > > Thanks,
> > > > > > > Phi|ip
> > > > > > 
> > > > > > --
> > > > > > Dr Sean Harmer | sean.harmer at kdab.com | Managing Director UK
> > > > > > KDAB (UK) Ltd, a KDAB Group company
> > > > > > Tel. +44 (0)1625 809908; Sweden (HQ) +46-563-540090
> > > > > > Mobile: +44 (0)7545 140604
> > > > > > KDAB - Qt Experts
> > > > > > _______________________________________________
> > > > > > Interest mailing list
> > > > > > Interest at qt-project.org
> > > > > > http://lists.qt-project.org/mailman/listinfo/interest
> > > > 
> > > > --
> > > > Dr Sean Harmer | sean.harmer at kdab.com | Managing Director UK
> > > > KDAB (UK) Ltd, a KDAB Group company
> > > > Tel. +44 (0)1625 809908; Sweden (HQ) +46-563-540090
> > > > Mobile: +44 (0)7545 140604
> > > > KDAB - Qt Experts
> > 
> > --
> > Dr Sean Harmer | sean.harmer at kdab.com | Managing Director UK
> > KDAB (UK) Ltd, a KDAB Group company
> > Tel. +44 (0)1625 809908; Sweden (HQ) +46-563-540090
> > Mobile: +44 (0)7545 140604
> > KDAB - Qt Experts
> > _______________________________________________
> > Interest mailing list
> > Interest at qt-project.org
> > http://lists.qt-project.org/mailman/listinfo/interest

-- 
Dr Sean Harmer | sean.harmer at kdab.com | Managing Director UK
KDAB (UK) Ltd, a KDAB Group company
Tel. +44 (0)1625 809908; Sweden (HQ) +46-563-540090
Mobile: +44 (0)7545 140604
KDAB - Qt Experts