I know this has been mentioned before somewhat in other topics about graphics settings, but I thought a topic just about disabling texture filtering would be easier to find for people.

You can't disable filtering from nGlide itself, so from the game's Galaxy screen, click the icon to the right of Play, choose "additional executables", then choose "config". Or, from the game's folder, run olcfg.exe.

Once you're in the config program, select "3Dfx Glide" under Display Driver, then click the Advanced button on the bottom left. Uncheck the boxes for "smooth out close-up textures" and "smooth out faraway textures", and click Accept. Back at the main config screen, click OK to close the program and save the changes. Make sure 3Dfx Glide is still selected when you click Ok, otherwise it changes to another display driver.

Now you can use nGlide for your main graphics and resolution settings, but without blurry texture filtering.