That is strange...I’m convinced it’s because your game has too much AA...wich leads to flat sun.
Have you tried to set BOTH (In your Nvidia control panel) global parameters tab and programs parameters tab, the gamma correction OFF and AA X4 multisampling ?
Just because sometimes Win10 doesn’t take in account only one of them...(it happened to me)
Have a look here, those are my Nvidia settings (for SH4 but works also for SH3!)
It’s in French but easily translated in english.
https://www.subsim.com/radioroom/sho...&postcount=107