[Interest] [QT3D] How Do I render multiple QEntities in different QViewports in C++?
Sean Harmer
sean.harmer at kdab.com
Sun May 1 18:04:38 CEST 2016
On Sunday 01 May 2016 09:15:52 Sean Harmer wrote:
> On 30/04/2016 21:02, Pierre Chicoine wrote:
> > Thank you Sean. Very descriptive. Since I have such a large system,
> > I will create an example and pass it to you.
> >
> > By the way a large percentage of your examples on 5.7 beta don't work.
> > But I'm sure you're aware of that.
>
> Yup, we're replacing something at the moment. Lots of commits lined up
> but the CI is broken.
I have fixes for almost all of the issues in the examples, locally now. Will
push and merge as soon as I can.
Cheers,
Sean
>
> Sean
>
> > Thank you again.
> >
> > On Apr 30, 2016 10:55 AM, "Sean Harmer" <sean.harmer at kdab.com
> >
> > <mailto:sean.harmer at kdab.com>> wrote:
> > > Hi,
> > >
> > > There's two things you need to consider:
> > >
> > > 1) The scene graph - the Entities that you wish to draw.
> > > 2) The framegraph - specifies the algorithm used to draw the scene graph
> > >
> > > I assume from your screenshot that you are more or less happy with
> >
> > defining
> >
> > > QEntity's to construct your scene graph. If you wish some entities
> >
> > to be drawn
> >
> > > in one part of the window (viewport) and the others in another
> >
> > viewport then
> >
> > > we need some way of saying "select this set of entities but not that
> >
> > set".
> >
> > > One way of doing this is by using a QLayer component attached to
> >
> > your entities
> >
> > > that says which layer that entity is part of. This is just like layers
> > > photoshop, gimp, blender etc. Create a QLayer, give it a name, and
> >
> > aggregate
> >
> > > it onto your QEntity as you do the other components (mesh, transform and
> > > material).
> > >
> > > Doing this doesn't change anything in the rendering on it's own. To
> >
> > affect the
> >
> > > change we also need to modify the framegraph. To do this, make sure the
> > > concept of the framegraph is clear in your mind. Have a read of:
> > >
> > > https://www.kdab.com/qt3d-2-0-framegraph/
> > >
> > > Each leaf node, corresponds to a portion of your overall scene. To
> >
> > keep things
> >
> > > simple, lets only consider the viewports and layer filters you will
> >
> > need. You
> >
> > > will need other things in the framegraph too (rendersurfaceselector
> >
> > (if using
> >
> > > 5.7), camera selector, technique selector etc). The parts of the
> >
> > framegraph
> >
> > > concerned with viewports and layers will look something like this:
> > >
> > > Root (e.g. TechniqueSelector)
> > >
> > > |- Viewport [left half of window]
> > > |
> > > |- LayerFilter [names="layer1"] (*)
> > > |
> > > |- Viewport [right half of window]
> > > |
> > > |- LayerFilter [names="layer2"] (**)
> > >
> > > Where:
> > >
> > > (*) <-- draws entities on "layer1" in left viewport
> > > (**) <-- draws entities on "layer2" in right viewport
> > >
> > > If you then want to use different cameras in the different viewports
> >
> > then you
> >
> > > can include a QCameraSelector node in each sub-tree.
> > >
> > > Root (e.g. TechniqueSelector)
> > >
> > > |- Viewport [left half of window]
> > > |
> > > |- CameraSelector [camera1]
> > > |
> > > |- LayerFilter [names="layer1"] (*)
> > > |
> > > |- Viewport [right half of window]
> > > |
> > > |- CameraSelector [camera2]
> > > |
> > > |- LayerFilter [names="layer2"] (**)
> > >
> > > Where:
> > >
> > > (*) <-- draws entities on "layer1" in left viewport using "camera1"
> > > (**) <-- draws entities on "layer2" in right viewport using "camera2"
> > >
> > > Hopefully that makes sense. In the future, I hope we can provide
> >
> > tooling and
> >
> > > perhaps higher level ways of building custom framegraphs. The
> >
> > framegraph is
> >
> > > hugely powerful as it totally allows changing the rendering algorithm at
> > > runtime without having to touch low level C++ graphics code.
> >
> > However, it is a
> >
> > > bit tricky to get to grips with at first.
> > >
> > > Cheers,
> > >
> > > Sean
> > >
> > > On Thursday 28 April 2016 13:34:58 Pierre Chicoine wrote:
> > > > Dear Sirs
> > > >
> > > > First: Thank you for Qt3d. The KDAB people are heroes in my book.
> > > >
> > > > I have two problems in C++ Qt3D.
> > > >
> > > > 1. I am having a difficult time figuring out how to render
> >
> > QEntities into
> >
> > > > separate QViewports. All my 3d objects draw to the first
> >
> > QViewport, the
> >
> > > > rest are black. I have read all your articles and comments
> >
> > everywhere on
> >
> > > > the Internet that I can find and I am basically confused.
> > > >
> > > > Is there a c++ example that would show multiple viewports with
> >
> > distinct
> >
> > > > separate QEntities? I can't seem to duplicate The QML example
> >
> > multiviewport
> >
> > > > in my code. What classes would get me there?
> > > >
> > > > 2. Also I'm also confused about QNodes and QEntitys and their
> > > > relationships. Maybe it's the use of Qt3d version 1 that is
> >
> > messing me up .
> >
> > > > I use to have a scene node and all the entities would hang off of
> >
> > one scene
> >
> > > > node for each scene. But that doesn't seem to work in version 2.
> >
> > Or do I
> >
> > > > use the addComponent on a QFrameGraph instead of a node? Or do I hang
> > > > Entities off of a viewport?
> > > >
> > > > Attached is a pic of my progress which draws all the objects into
> >
> > the same
> >
> > > > viewport. The window tiles 2 windows properly but I only draw to one
> > > > viewport, the second or third stay black. The code here is what I
> >
> > repeat in
> >
> > > > each scene class. It's a bit of a mess thrown together to test
> >
> > Qt3D classes
> >
> > > > because I don't understand the relationships between all the Qt3D
> >
> > classes
> >
> > > > used to place objects in a viewport.
> > > >
> > > > Qt3DCore::QCamera *cameraEntity = new Qt3DCore::QCamera(
> >
> > pParentNode);
> >
> > > > cameraEntity->setObjectName(QStringLiteral("cameraEntity"));
> >
> > cameraEntity->setProjectionType(Qt3DCore::QCameraLens::PerspectiveProjecti
> > o
> >
> > > > n);
> > > >
> > > > cameraEntity->setAspectRatio(1024 / 768);
> > > >
> > > > cameraEntity->setUpVector(QVector3D(0.0f, 1.0f, 0.0f));
> > > >
> > > > cameraEntity->setViewCenter(QVector3D(0.0f, 3.5f, 0.0f));
> > > >
> > > > //cameraEntity->lens()->setPerspectiveProjection(60.0f, 16.0f/9.0f,
> > > > 0.1f, 1000.0f);
> > > >
> > > > if(pScenesSet) // if it's a scene then we want to set it where
> >
> > they want it
> >
> > > > cameraEntity->setPosition(QVector3D(pScenesSet->CamXPos - 20,
> > > >
> > > > pScenesSet->CamYPos + 80, pScenesSet->CamZPos));
> > > >
> > > > else // so it's a schematic
> > > >
> > > > cameraEntity->setPosition(QVector3D(-20, 65, 180));
> > > >
> > > > theApp->input->setCamera(cameraEntity); // not sure about this
> > > >
> > > > relationship??
> > > >
> > > > // FrameGraph
> > > >
> > > > pQFrameGraph = new Qt3DRender::QFrameGraph();
> > > >
> > > > pQTechniqueFilter = new Qt3DRender::QTechniqueFilter();
> > > >
> > > > pQViewport = new Qt3DRender::QViewport(pQTechniqueFilter);
> > > >
> > > > Qt3DRender::QClearBuffer *clearBuffer = new
> > > >
> > > > Qt3DRender::QClearBuffer(pQViewport);
> > > >
> > > > Qt3DRender::QCameraSelector *cameraSelector = new
> > > >
> > > > Qt3DRender::QCameraSelector(clearBuffer);
> > > >
> > > > Qt3DRender::QRenderPassFilter * pQRenderPassFilter = new
> > > >
> > > > Qt3DRender::QRenderPassFilter(cameraSelector);
> > > >
> > > > Qt3DRender::QRenderTargetSelector * m_gBufferTargetSelector = new
> > > >
> > > > Qt3DRender::QRenderTargetSelector(pQTechniqueFilter);
> > > >
> > > > // Qt3DRender::QLayerFilter * m_sceneFilter = new
> > > > Qt3DRender::QLayerFilter(theApp->pCThreeDWindow);
> > > >
> > > > // TechiqueFilter and renderPassFilter are not implement yet
> > > >
> > > > pQViewport->setRect(QRectF(0, 0, 1, 1));
> > > >
> > > > clearBuffer->setBuffers(Qt3DRender::QClearBuffer::ColorDepthBuffer);
> > > >
> > > > pQFrameGraph->setActiveFrameGraph(pQTechniqueFilter);
> > > >
> > > > // Setting the pQFrameGraph
> > > >
> > > >
> > > > // I add a framegraph component to: class CThreeDWindow : public
> > > >
> > > > Qt3DCore::QEntity
> > > >
> > > > // public:
> > > >
> > > > // CThreeDWindow(Qt3DCore::QNode *parent = 0);
> > > >
> > > > theApp->pCThreeDWindow->addComponent(pQFrameGraph);
> > > >
> > > > if(pScenesSet) // if it's a scene then we want to set it where
> >
> > they want it
> >
> > > > pQViewport->setClearColor(QColor(pScenesSet->BackRed,
> > > >
> > > > pScenesSet->BackGreen, pScenesSet->BackBlue));
> > > >
> > > > else
> > > >
> > > > pQViewport->setClearColor(QColor(0, 0, 0));
> > > >
> > > > cameraSelector->setCamera(cameraEntity);
> > > >
> > > > //m_gBufferTargetSelector->setTarget(m_sceneFilter);
> > > >
> > > >
> > > >
> > > > Any help would be appreciated.
> > > >
> > > > Thank you
> > >
> > > --
> > > Dr Sean Harmer | sean.harmer at kdab.com <mailto:sean.harmer at kdab.com>
> > >
> > | Managing Director UK
> > |
> > > Klarälvdalens Datakonsult AB, a KDAB Group company
> > > Tel. UK +44 (0)1625 809908, Sweden (HQ) +46-563-540090
> > > KDAB - Qt Experts - Platform-independent software solutions
> >
> > _______________________________________________
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> > Interest at qt-project.org
> > http://lists.qt-project.org/mailman/listinfo/interest
--
Dr Sean Harmer | sean.harmer at kdab.com | Managing Director UK
Klarälvdalens Datakonsult AB, a KDAB Group company
Tel. UK +44 (0)1625 809908, Sweden (HQ) +46-563-540090
KDAB - Qt Experts - Platform-independent software solutions
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