I have gigapixel a.i. but like I said I dont want to take the time yet. It requires someone who loves this game to literally play the game, it scans the textures in real time, and that gives you access to them to a.i. upscale them, so you can inject them later when youre done. I simply cannot dedicate that much time to a single game, or id never get anything done.
There is a more obtuse but free a.i. upscale technology called ESRGAN which will only work with nvidia (requires cuda) and you have to mess with a higher level programming language interface which can be intimidating.
Gigapixel will resolve more generalistically but its aslo idiot proof which in my view.... the more user friendly it is, the more I like it. It shouldnt be a rubics cube for every little thing which retro modding is definitely the hardest because it can barely work correctly to begin with on modern operating systems.
ESRGAN resolves along the lines of whatever you trained it to look like and it also can take days to train a model. If you were extremely devoted you can technically train it on very specific images per game targeted object and get superior results, but its really not worth it unless you have real passion propelling said goal. It can literally look at an image of say a trees bark, and all the ways trees bark is supposed to look like from its training, and blend the original game art with the details you find in actual nature.
There is another upscaler called wafu or something rather, but in all honesty its not as sophisticated as the other methods but if its the only thing you have, then its better than nothing.
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Just immerse yourself in everything texmod. Ideally I farm this out as community homework. Someone needs to get involved. This is an insane amount of work, but it needs to be done since no one else will. And the people who do, generally privatize their work. Honestly thats a good thing because a great deal of it is honestly trash. Youre going to want to try this one out though. It makes the game look a lot less flat. More 3 dimensional. More believable lighting just period.