here's a bug about QtConcurrent and qml-Scene3D, which makes program blocking.

in a qt3d program, QtConcurrent seems conflicked with Scene3D item. it makes application blicking, with cpu high usage (more than 80% as usually), and the UI is NOT active as well, some ui item won't render.

i do a testing on Qt official example : advancedcustommaterial.pro.

i add the next code to this example, it reproduces the situation that i described.

QtConcurrent::run(func, args);

if i replace with qthread, such as :
 

MyQThread mythread;
MyQThread ::run() \{ func(args); }
mythread.start();

this won't occur mistakes, so it must be problem to QtConcurrent with qt3d/Scene3D, in Qt ver: 5.14.2, Win32 platform(no extra gpu, with cpu only).