The graphics setup in the original game as you've mentioned it above allows you to set those options manually according to which ones were supported by your gpu's D3d drivers at the time. If a particular function, say, trilinear filtering, was not supported by your gpu you could disable it from the advanced 3d config tab--in case the game might've crashed with it selected...;) As you notice, it is possible to set all three at the same time, which is easy to do today because all 3d gpu drivers support all three selections. I run the game with all three selected and my gpu drivers automatically use the best mode possible of the three, depending on what the game is asking the gpu to render at any given time.

Went back and played the game a bit more today, and I noticed a couple of things relative to your question:

*The game seems to always use Trilinear/Mipmap even if I have Bilinear checked as well--ie, I haven't seen a situation in which the game actually uses Bilinear at any time so long as I have trilinear selected at the same time .

*Trilinear filtering, as you might expect, was a more recent development than Bilinear, and you'll notice that you cannot select Bilinear & mipmaps simultaneously, as the trilinear setting automatically enables mipmaps as the game requires them when doing trilinear filtering (you cannot set mipmaps on by itself, but when you select trilinear, mipmaps are also selected by the game software at the same time.)

Bi/Tri-linear are both forms of texture filtering, and even though Trilinear filtering is newer than Bilinear, the most advanced form of texturing filtering is one developed only after the game shipped, called "Anisotropic filtering." It is superior to Trilinear, and you can actually force it to run with the game instead of Trilinear filtering by simply setting up a profile for Overseer in your gpu drivers and setting the texturing filtering section of your profile to override the game settings and use Anisotropic filtering instead. That's how I run the game, forcing on a 16x level of Anisotropic filtering in my Catalyst control panel (I have an AMD gpu.) In these older D3d games like Overseer, current drivers allow the user to override the in-game settings for a number of things besides texture filtering--like for instance FSAA, vsync settings, etc. *Do not use "Morphological filtering" with this game, however--in case you are running an AMD gpu--the nVidia counterpart is called "FXAA," I believe--don't use it, either. Just override the game's texture filtering and FSAA settings if you like.

*I *hope* this helped and didn't increase your anxiety/confusion on the subject...;)