Unfortunately due to the implementation of OpenGL Hardware Acceleration in Affinity, we're unable to ever support GPUs that do not use DX11 feature set 12_0 or later and the GTX 660 only supports feature set 11_0, my apologies.
Unfortunately due to the implementation of OpenGL Hardware Acceleration in Affinity, we're unable to ever support GPUs that do not use DX11 feature set 12_0 or later and the GTX 660 only supports feature set 11_0, my apologies.