Hi all, For a project I'm working on I need to create 3D objects whose geometry depends on data coming from an external input line: so, to test the whole mechanism, I'm trying to use Qt3D to spawn objects with custom geometry inside an event triggered by a timer. I tried using both Qt v5.6.1 and Qt v5.7.0 and I got different (and, in my opinion, odd) behaviours.
Here is my QML Timer code:
Timer
{
id: spawnTrigger
interval: 1000
running: true
repeat: true
triggeredOnStart: true
onTriggered:
{
var randomX = Math.random() * 20 - 10;
SceneManager.spawnCustomGeometry(sceneRoot, Qt.vector3d(randomX, 0, 0));
}
//This works fine.
//Component.onCompleted:
//{
// var randomX = Math.random() * 20 - 10;
// SceneManager.spawnCustomGeometry(sceneRoot, Qt.vector3d(randomX, 0,
0));
//}
}
The 'SceneManager.spawnCustomGeometry()' function uses the 'createObject()'
function to instantiate the custom geometry described inside a QML file,
which is loaded via Qt.createComponent().
The behaviour I get is the following:
- Using Qt v5.6.1:
- If the 'triggeredOnStart' property is set to false, the custom geometry
does not show up and the application continues running.
- If the 'triggeredOnStart' property is set to true, the custom geometry
shows up just once and the application continues running.
- Using Qt v5.7.0:
- If the 'triggeredOnStart' property is set to false, the custom geometry
does not show up and the application crashes.
- If the 'triggeredOnStart' property is set to true, the custom geometry
shows up just once and the application crashes.
With Qt v5.7.0, in both cases the call stack is the following (so far it has
been the same for every crash):
- Call stack on Windows 7 x64 OS with MinGW32:
1 QMetaObject::inherits qmetaobject.cpp 339
0x8d12b1
2 Qt3DRender::Render::Entity::sceneChangeEvent entity.cpp 213
0x3bf9bdf9
3 Qt3DCore::QBackendNodePrivate::sceneChangeEvent qbackendnode.cpp 82
0x380cfa1b
4 Qt3DCore::QChangeArbiter::distributeQueueChanges qchangearbiter.cpp 132
0x380c1f12
5 Qt3DCore::QChangeArbiter::syncChanges qchangearbiter.cpp 179
0x380c21c0
6 Qt3DCore::QAspectManager::exec qaspectmanager.cpp 273
0x380c7e07
7 Qt3DCore::QAspectThread::run qaspectthread.cpp 85
0x380c8772
8 QThreadPrivate::start(void *) *4 qthread_win.cpp 391
0x78b777
9 msvcrt!_itow_s
0x76541287
10 msvcrt!_endthreadex
0x76541328
11 KERNEL32!BaseThreadInitThunk
0x7673337a
12 ntdll!RtlInitializeExceptionChain
0x76ef92e2
13 ntdll!RtlInitializeExceptionChain
0x76ef92b5
14 ??
- Call stack on Ubuntu Linux 14.04 x64:
1 QMetaObject::inherits(QMetaObject const *) const
0x7ffff65a8045
2 ??
0x7fffde2d0d77
3
Qt3DCore::QChangeArbiter::distributeQueueChanges(std::vector<QSharedPointer<Qt3DCore::QSceneChange>>
*) 0x7fffddb923d8
4 Qt3DCore::QChangeArbiter::syncChanges()
0x7fffddb9255f
5 Qt3DCore::QAspectManager::exec()
0x7fffddb9e6e6
6 ??
0x7fffddb9fa92
7 ??
0x7ffff63d95f9
8 start_thread
pthread_create.c 312 0x7ffff54db184
9 clone
clone.S 111 0x7ffff5b4937d
By the log messages I put inside the 'SceneManager.spawnCustomGeometry()'
function, I can tell for sure that the call to 'createObject()' is being
performed every time the timer event is triggered (as expected).
>From the results I got, it seems to me that no custom geometry can be
>instantiated once the parent object creation has been fully completed.
Am I right or did I overlook something important?
I have attached the test applications source code to this message, in case
anyone needs it.
Any help would be greatly appreciated!
Best regards,
Carlo
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Test_Qt.7z
Description: Test_Qt.7z
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