Setting TrackHMD to false disables rendering in vtkOpenVRRenderWindow
If one calls SetTrackHMD(false) on a vtkOpenVRRenderWindow, the application ceases rendering.
I've identified that
vr::VRCompositor()->WaitGetPoses(this->TrackedDevicePose, vr::k_unMaxTrackedDeviceCount, nullptr, 0);
must be called in order for rendering to function.