MSAA forced through the Nvidia Control Panel or Nvidia Inspector seems to work pretty well with Slave Zero using nGlide.

Transparency antialiasing also has a nice side-effect - it reduces distant texture shimmering/aliasing (which I think is caused by broken/non-existent mipmapping or possibly negative LOD bias in the game's Glide mode - it's not present in Direct3D mode).

No antialiasing
8x MSAA (notice border of the orange sign and the distant road)
8x MSAA with 8x transparency supersampling (notice the distant wall texture - it looks much better in motion)

Haven't encountered any glitches with it so far.
Not sure how much of a performance impact this would have on low-end or older hardware.

how did you get D3D mode to work?

See these instructions.

Direct3D mode gets you bump-mapping, better texture filtering / mipmapping and possibly better performance, but restricts your resolution options, (probably) limits you to 16-bit colour (making the true colour textures option ineffective) and might encounter a compatibility issue on recent hardware which makes it revert to using a very low quality z-buffer (resulting in and flickering on many objects). Also [url=http://www.gog.com/forum/slave_zero/true_color_textures_bump_mapping/post12]crosshair offset bug at resolutions over 640x480.

Driver-forced AA works with Direct3D mode as well, it looks like this (sadly I'm getting the aforementioned z-buffer issue - see the walls clipping through each other and the sign in the distance, and the vertical lines through the nearby sign)

thank you: ) it isnt working though. which nv drivers are you using and which GPU do you have?

337.50 beta drivers
GeForce GTX770

(I've also seen Direct3D work on a 9500GT using 335.23 and later 337.50 drivers, which didn't have the low-quality z-buffer issue)

EDIT: not sure if it could help at all, but this is what my options screen looks like in Direct3D mode

thanks for replying again. i got it working but stuck in 16 bit color

No problem, hope that post helped.

Direct3D mode only seems to work in 16-bit colour on recent hardware / operating systems, I'm not sure why.

Are you getting the low-quality z-buffer issue as well?

yes i am and i wish nvidia would fix it. the z-buffer actually looks compressed with all games on every driver compatible with my 780 so i am guessing the z-fighting in slave zero is an optimization nvidia is forcing.

Hmm, I haven't really noticed it in other games (aside from what they've had on all hardware I've played them on)

Slave Zero in Direct3D seems to be reverting to some extremely low precision mode that makes 16-bit Z look great in comparison.
I tried tweaking a few settings in szOptions.ini:

The obvious one "Force 32 Bit Depth Buffer" set to 1 results in Direct3D mode becoming impossible to switch to or crashing.

"Force Two Pass Rendering" set to 0 makes the clipping issues slightly less prominent, but also makes lighting much dimmer.

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nGlide mode has no noticeable z-fighting issues

here is a fix that i hope you will enjoy from a really cool person:
https://forums.geforce.com/default/topic/744902/geforce-drivers/slave-zero-z-fighting-issue/

Wow O_o

Not only did it fix the z-fighting, now the game runs with 32-bit colour and in non-stretched widescreen (aside from the HUD) - "really cool" is right :D

Had to tweak the file paths in szOptions.ini to get it working on my install.

I'll have to see if I can find a way to fix the crosshair offset issue.

EDIT: just don't try to change it back to a 4:3 resolution, the field of view change makes it look a bit odd :P

EDIT2: not caused by this tweak, but just noticed the game seems to have a graphical issue with Slave Zero's model if you have bump mapping enabled and load a save on the level "TRAINWRECK A". Issue goes away once you progress to the next level. Not sure if this happens on other levels

EDIT3: Oh damn, lock-ons for the missile launcher don't work :(
1920x1080, 1440x1080, 1600x900 missile launcher won't lock on.
Set it to 1280x960 and it starts working again

Bump for edits to my previous post and to say that I haven't had any luck with the crosshair offset issue in D3D (which is probably the cause of broken lock-on in high resolutions).