I want to use Qt3D within Qt5.7 to plot a 3D scene (a chemical molecule) which I want to rotate. The problem is that my 3D objects are not displayed according to their spatial positioning. The last created QEntity is always in the foreground, regardless of how I rotate the camera. In the minimum working example below, the QEntity smallGreenSphere is always in the foreground even though it is spatially positioned behind bigRedSphere in the default view specified in the camera settings. To rephrase the problem: My 3D scene has no depth. Please note that smallGreenSphere is instantiated after bigRedSphere in the main.cpp file shown below: #include <QGuiApplication> #include <Qt3DCore> #include <Qt3DRender> #include <Qt3DExtras> Qt3DCore::QEntity* createTestScene() { Qt3DCore::QEntity* root = new Qt3DCore::QEntity; Qt3DCore::QEntity* bigRedSphere = new Qt3DCore::QEntity(root); Qt3DCore::QEntity* smallGreenSphere = new Qt3DCore::QEntity(root); Qt3DExtras::QSphereMesh* bigMesh = new Qt3DExtras::QSphereMesh; bigMesh->setRadius(5); bigMesh->setRings(100); bigMesh->setSlices(20); Qt3DExtras::QSphereMesh* smallMesh = new Qt3DExtras::QSphereMesh; smallMesh->setRadius(2); smallMesh->setRings(100); smallMesh->setSlices(20); Qt3DExtras::QPhongMaterial* redMaterial = new Qt3DExtras::QPhongMaterial; redMaterial->setSpecular(Qt::white); redMaterial->setShininess(10); redMaterial->setAmbient(Qt::red); Qt3DExtras::QPhongMaterial* greenMaterial = new Qt3DExtras::QPhongMaterial; greenMaterial->setSpecular(Qt::white); greenMaterial->setShininess(10); greenMaterial->setAmbient(Qt::green); Qt3DCore::QTransform* transform = new Qt3DCore::QTransform; transform->setTranslation(QVector3D(0,0,10)); bigRedSphere->addComponent(redMaterial); bigRedSphere->addComponent(bigMesh); smallGreenSphere->addComponent(greenMaterial); smallGreenSphere->addComponent(smallMesh); smallGreenSphere->addComponent(transform); return root; } int main(int argc, char* argv[]) { QGuiApplication app(argc, argv); Qt3DExtras::Qt3DWindow view; Qt3DCore::QEntity* scene = createTestScene(); // camera Qt3DRender::QCamera *camera = view.camera(); camera->lens()->setPerspectiveProjection(45, 16./9., 0.1,1000.); camera->setPosition(QVector3D(30., 0, 60.)); camera->setViewCenter(QVector3D(0, 0, 0)); // manipulator Qt3DExtras::QOrbitCameraController* manipulator = new Qt3DExtras::QOrbitCameraController(scene); manipulator->setLinearSpeed(50); manipulator->setLookSpeed(180); manipulator->setCamera(camera); view.setRootEntity(scene); view.show(); return app.exec(); } This results in the following scene: Please note that I did not rotate anything manually and that this is the output of the code above. If I now swap the order of instantiation in createTestScene() by Qt3DCore::QEntity* smallGreenSphere = new Qt3DCore::QEntity(root); Qt3DCore::QEntity* bigRedSphere = new Qt3DCore::QEntity(root); so that bigRedSphere is now instantiated after smallGreenSphere , the bigRedSphere is always in the foreground and the resulting scene (again without manual rotation) looks like this: This proves that the order of instantiation determines what sphere is displayed in the foreground. How can I obtain the correct 3D view regardless of the order of instantiation? Do I have to use some different rendering technique? Thanks in advance for your help and please consider that I am new to Qt, Qt3D, and rendering in your answer.

For further reference this issue seems solved as described in this post .

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A weird bug? Why is there no spatial depth in my 3D scene?

Unsolved General and Desktop

29 Posts 5 Posters 12.5k Views

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kshegunov Moderators
replied to Finn on last edited by

#17

Honestly, I'd be surprised if there was a difference between using cmake and qmake. And to be completely frank I don't know what might be the cause of the problem. My current best advice is to either bring the question to the mailing list, where hopefully one of the developers of Qt3D will pick it up (but after you check there's no open bugs on this), or try and wait for some other suggestion from other of our members here.

Kind regards.
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Finn
replied to kshegunov on last edited by Finn

#18

I tried it on my private MacBook Pro with MacOS Sierra 10.12.1 and installed Qt5 via brew install qt5. The result is still the same. What on earth can be the reason that it is working for you guys and not for me? Do I need some other libraries or build options?
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A Former User
wrote on last edited by

#19

Sorry, as a noobie, I can't offer any insight, but I ran the code, and I'm getting the same as Finn. I'm on Qt 5.7 on Win 10.

Could it be CPU or GPU related? I'm on a 6coreAMD machine.
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Finn
replied to A Former User on last edited by

#20

@Ian-Bray Thank you for your reply, this was very helpful! I would suggest that someone more experienced than me should report this as a bug.
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kshegunov Moderators
replied to Finn on last edited by kshegunov

#21

@Finn said in A weird bug? Why is there no spatial depth in my 3D scene?:

this was very helpfu

Indeed, it was.

I would suggest that someone more experienced than me should report this as a bug.

There's nothing to it, you just describe the problem and attach the screenshots and the code from upstairs as a minimal reproducible example (preferably with a simple project file). As for the problem itself it may be helpful if we can squeeze some more information out. I may be running a newer (or older) version of Qt compared to you. Can you both state the full version (with patch number). I'm running Qt 5.7.2 built from git some time ago on a Linux 4.8.11 kernel.
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A Former User
replied to kshegunov on last edited by

#22

@kshegunov

I'm using qt-opensource-windows-x86-mingw530-5.7.0 on Win 10, if I get a chance I'll try it on Linux later.
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A Former User
wrote on last edited by

#23

Sorry, this isn't going to be helpful. Just to report that both slabs of code crashed on Qt 5.7.1 GCC 64 on latest Mint.
Possibly due to lack of RAM. Not sure.
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Finn
replied to A Former User on last edited by

#24

@Ian-Bray With Qt 5.7.1 the example works now perfectly fine for me.
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kshegunov Moderators
replied to Finn on last edited by

#25

Then probably it's a bug that was fixed with the patch version in the meantime. Cheers!
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A Former User
replied to Finn on last edited by

#26

@Finn Thanks Finn. I'll update later!
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A Former User
replied to kshegunov on last edited by

#27

@kshegunov Must have been quite a big one. I ran the 3d Materials Example on 5.7.0 two days ago - it was horrible. I updated to 5.7.1 yesterday and ran it again - works perfect now.
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kshegunov Moderators
replied to A Former User on last edited by

#28

Well, 5.7.0 was Qt3D's first official release, and the code hasn't matured as much as the other modules, so some bumps along the road are expected. My biggest beef with Qt3D actually is its very thin documentation, but I'm sure that'll improve with time.:)
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Pablo J. Rogina
replied to Finn on last edited by

#29

For further reference this issue seems solved as described in this post.
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