To get z-depth data out of Softimage with Arnold, you can use the built-in Softimage Depth render channel. Depth outputs a floating point image, so you need to use a format like EXR.
The Depth channel will give you non-antialised, non-normalized depth data in the alpha channel. In the DCC, it will appear solid white, but that’s because the data is non-normalized.
Non-normalized means that the Z depth values are not between 0 and 1, but between the near and far camera clipping planes, so you need to divide the Z values by the far clipping plane value to get 0..1 values. You can use a compositing package like Nuke for this. Myself, I don’t have Nuke, so I used Composite to normalize the Z depth AOV:
In Maya, you’d use the Z AOV to render out the Z-depth information. In Softimage, Depth is mapped to the Z AOV, and if you export a .ass, you’ll see the “Z” AOV listed in the options node.
outputs 2 1 STRING "RGBA RGBA sitoa_output_filter Passes.Default_Pass.Main" "Z FLOAT sitoa_closest_filter Passes.Default_Pass.Depth"
Arnold Support Corner 
When I try to add the MTOA Z-depth AOV the resulting EXR appears to remain completely black and empty while further color information is rendered fine..
Might I overlook something here?
Hi
I did a quick test in Maya, and I got a good Z AOV with alpha values. I didn’t really do anything special, just added the Z AOV.
Where are you viewing the Z AOV?
Hello ! i’m still trying to get a zdepth pass with Arnold, could you share the scripts needed to be applied on exr in Composite to normalize the EXR ? I’ve try to copy yours on the printscreen, but doesnt work … thks for your help ! big python newb …
ps : perhaps the way we can get the zdepth pass has change since 2012 ? 😉
Hello ! thks for this tip but could you share the script used in Composite to normalize the Zdepth file ?
Or things have changed since last year to get that zdepth pass with Arnold ?
Thanks !