krakatoa for max has an option for using an exr with zdepth information to matte the render. In maya, however, I only saw a place to input deep dtex files. does maya support conventional zdepth files to matte the render?
Alternatively, do you plan to support exr2 deep files for mattes in maya?
Krakatoa for Maya does not support exporting shadows the same way Krakatoa for 3ds Max does. This is due to limitations in Maya’s API that we have discussed with Autodesk.
A little explanation on that:
Krakatoa for 3ds Max writes a specially formatted exr file. This is a custom format that we made that contains multiple layers of data. We then wrote a 3ds Max shadow plugin that could interpret these special files. The reason we have not done this in Maya is because Maya does not support the ability to write custom shadow plugins, and therefore we cannot use our format in 3rd party Maya renderers (like VRay, etc). I had a hack that “sort of” worked by placing a special texture map in the light’s “color” channel, but it was really ugly and confusing, so I didn’t end up including it.
So that’s the reason why we haven’t been able to achieve the same level of integration as our 3ds Max plugin. The closest we came in Maya was to support RenderMan’s “dtex” deep shadow format, but that is only good if you’re using Krakatoa with RenderMan since nothing else reads dtex files.
We would like to support EXR 2.0 files for shadows. However, I don’t know of any renderers that would import these shadow maps in Maya (are there any that you know of?).
I see, however, I was not referring to shadows, I want to avoid rendering particles that are inside a matte area (holdout matte). So I’d like to use a zdepth exr image sequence as an input for a matte into Krakatoa instead of a matte object in the scene.
Since the original geometry that I’d like to use as a matte object was generated outside of maya, and was also displaced, it would be great to use the zdepth of the render pass as a holdout matte. This is a great feature in Krakatoa for max, however it looks like Krakatoa maya only supports dtex files as holdout mattes. Unfortunately, the other render was not generated in Renderman, so dtex is not a feasible option.
Whoops. I should have read your question more closely 
You are correct, we don’t currently support using a z-depth image as a matte. That is a very good idea though, I have added it to my “to do” list.
For now the only option is tag the matte geometry and have Krakatoa compute the z-depths itself. Are you able to use the meshes themselves to create mattes in your case?
“Are you able to use the meshes themselves to create mattes in your case?”
Not really, because the displacement is calculated in a shader from another renderer (not renderman), so the matte would not line up. For now, I’ve used a completely alternative solution to complete the task at hand.
If there was a way to convert a zdepth exr into a (fake) deep image dtex, perhaps that would be an adequate temporary solution. I couldn’t find a way to do that yet with renderman or nuke though…
I believe I’ll just have to add importing of z-depth exr mattes as a new feature. I consider it a missing feature.