I did try that, yeah.
Sorry my original post was a little light on details, I'm running Win7 32bit. I have made some progress in the time that's passed but to answer your question, with the desktop set at 1280x720 the game still launched in 1920x1080. I tried everything I could think of to force it, tried messing around with RivaTuner & Powerstrip but it seems the existing solution sets the game to your native resolution, and that's that (I did read somewhere that setting options.ini's 'resolution' line to -1 or -3 does exactly that - I'm sure I tried -2 as well and I don't recall seeing anything other than my native res). While I wasn't able to force the resolution, I could use Rivatuner or Powerstrip to force the refresh rate - so I made it run in 1920x1080x24Hz which was deemed acceptable for 3D by Nvidia and my TV. That low refresh rate was not as bad as I expected, but still kinda rough when the camera is moving (looking around) - it was great to see the 3D effect, but this was not good enough for prolonged play.
Anyway, after that I found two more recent patches which I think might be worth adding into the Thief 3 solution here. Took me ages to find them, they didn't come up in my google searches but I eventually found them in the ttlg forums. They both essentially do the same thing - let you replace the in-game resolution options with custom resolutions - so they would replace the current "step 2" (editing options.ini) and you'd no longer get that bizarre numeric value appearing in the in-game options. To get the FOV right, you still need to use the FOV patch and start a new game.
The first is an exe that lets you edit the in-game resolution options to whatever you want, and it also includes a "crash fix" option (I think this is for a crash that occurs when saving & loading, entering level end/transition points, etc. in Win 7/Vista). I still get those crashes unfortunately, but everyone else has reported great success with this patch. The resolution changes work fine for me, I can set whatever I want.
Hadley's patch:
Author's link (.exe download)
mirror (.zip download)
discussion on ttlg
The second is a replacement T3Main.exe that already has the in-game options edited to a selection of 16:10 resolutions.
Massimiliano Goi's patch:
on ttlg forums
on eidosgames forums
Those resolutions are no good to me, but the readme contains the instructions on how to hex edit the resolution options in T3Main.exe. I tried the first patch, got the game running in 1280x720 60Hz and in 3D, but it still crashes at the same predictable moments (without Hadley's crash fix it enters an infinite loop which is what many people have been getting; with the crash fix my infinite loop becomes a crash-to-desktop, but this fix seems to work for everyone else :/ ). I went back to the original exe and used Massimiliano Goi's instructions to edit my own desired resolution into it - the resolution works fine but the crashes are exactly the same.
It only does it in 16:9 resolutions - 16:10 and 4:3 all work fine. The crashes all occur when a confirmation message is supposed to appear on screen - when ending a level/changing to a different map, loading a saved game from the menu, etc. I'm looking in the game's default.ini to see if I can find any info regarding those screens and mess with it.
I've tried all the usual suggestions - disable dual core, disable SLI, use basic visual theme, compatibility modes, etc. - none of these things have made a difference for me.
Anyway, I'm not sure this is the right forum to try to solve my crash bug - suffice to say I can get the game running in widescreen & 3D and it looks great. I know when the crashes will occur so I can avoid them by changing resolution with the in-game options, then changing back afterwards. Bit of an ugly workaround, and gets irritating in the street sections when you're changing maps quite frequently, but it'll do for now.
Are either of those patches useful for the game's solution here?