As FulVal suggested, it can be done with dgVoodoo. I've just confirmed that, with it, software mode works fullscreen with the full-sized HUD and sepia effects. Here are instructions:
Note: The following is for DirectX 10 and later GPUs, since the dgVoodoo 2 wrapper requires it. For older, pre-2007 GPUs, follow the instructions at the bottom of this post for dgVoodoo 1.5, instead.
1. Download the
dgVoodoo 2 wrapper.
2. Extract
dgVoodooCpl.exe,
MS\DDraw.dll and
MS\D3DImm.dll to your game folder. Don't extract the MS folder, itself.
3. Run
dgVoodooCpl.exe from your game folder.
4. Click the
[ .\ ] button in the upper-right corner to set the config folder to your game folder.
5. On the
General tab, set
Scaling mode to
Stretched, keep Aspect Ratio. That keeps the gameplay and movies in the intended 4:3 ratio (so there will be black bars on the sides on widescreen monitors) and seems to be necessary to get the nice sepia fade-in effect when maps first load.
6. Switch to the
DirectX tab and set
Videocard to
dgVoodoo Virtual SVGA Card (this is the key setting to force software rendering).
7. Remove the checkmark from
dgVoodoo Watermark at the bottom and click the
OK button.
8. Run
olcfg.exe.
9. Select
Direct3D [HW Accelerated] and, preferably, the highest resolution that your monitor supports, then click
OK.
(If you're wondering what to set on the
Advanced page, it doesn't seem to me to make any difference when forcing software mode.)
10. Once you're in a level, press the minus (-) key to bring up the full-sized HUD (i.e. make the gold bar which says "ammo," "health," etc. appear at the bottom).
Note: When a level starts, you may get a warning message about failing to enable 3D acceleration. You can ignore it because you want it disabled to get software rendering.
Note #2: There's another method that involves adding
LECDDRAW.DLL to give you a "DirectDraw" option in olcfg.exe, but I found that it still requires dgVoodoo and limits you to no higher than 800x600 (with the method above, you can go up to 1600x1200).
Edit: Here are the instructions for pre-DirectX 10 GPUs:
1. Download the
dgVoodoo 1.50 Beta 2 wrapper.
2. Extract
dgVoodooSetup.exe,
glide.dll and
glide2x.dll to your game folder.
3. Download and extract [url=http://jkdf2.com/files/ddraw_(hack_viewport3_clear2).zip]this ddraw.dll wrapper[/url] to your game folder.
4. Run
olcfg.exe and select 3Dfx Glide mode.
5. Once you're in a level, press the minus (-) key to bring up the full-sized HUD (i.e. make the gold bar which says "ammo," "health," etc. appear at the bottom).
If the game doesn't automatically run in software mode or not how you'd like, run dgVoodooSetup.exe and play around with the settings in it.
