When I run this app on Roku Stick (3600X, Display set to 1080p, FW 7.2.0 4100-24). The scene rendered in 1080p. How in code I get that scene rendered in FHD?
In other words, even if your device is configured and outputs 1080p (FHD) signal to the TV, your programmatic resolution remains 720 (HD) on the #3600 stick - which gets upscaled to FHD and multiplexed with video.
And then on a 4k device you can at best address 1920x1080, even as the signal output be 3840x2160.