non-blocking multi-threaded OpenGL rendering in Qt 5
This is a simple proof of concept application written in C++ using Qt 5 and OpenGL. The goal was to have the Qt GUI never "block" waiting for OpenGL rendering (in case it is slow). This means the rendering should be done in an asynchronous fashion. The rendering thread should be producing frames and the main thread be consuming them, but the main thread should never wait for the producing thread. It is acceptable for the consuming thread to wait for the main thread. Conceptually, it is like a ring buffer.
Slow OpenGL code is simulated by an artificial 250 millisecond delay put into the middle of the OpenGL drawing calls. For the demo app, this delay can be enabled/disabled via the GUI.
This demo achieves the non-blocking behavior by using off-screen OpenGL rendering to a QImage in a secondary thread. This is not ideal is there is a performance penalty for copying so much data between threads, as well as displaying a QImage rather than a QPixmap on a QWidget. The CPU usage seems to be a function of the QImage resolution.
- Qt5 (widgets)
The relevant development package to install on Ubuntu 18.04 is:
- qt5-default
qmake
make
./opengl_thread_test