Guidance: Z-Depth workflow?

[hilaire.gagne]

Hi Folks,

I'm attempting to render a depth pass (z-depth) using Maya 2014 SP3 and am encountering some issues; specifically around the proper workflow to render out the pass.

Scene Specifics:

Linear Workflow as per Maya documentation

Physical Sun & Sky

spotlights /w fog

mia_materials_x_passes

mia_car_paint_phen_x_passes

truck model includes mirror & glass mia materials

What I've done so far:

1. Created a new Render Layer

2. Added geometry to layer

3. Assigned Luminance Depth Preset

4. Break Connection on Shading Group for layer

5. Re-select geometry in layer and re-apply Surface Shader material override

6. Did not apply (excluded) Surface Shader on Glass material

7. Enable Propagate Alpha in Glass material

8. Adjusted Camera Clip Near/Far for scene

9. Adjusted the SetRange utility node attributes (Min/Max) to match Camera Clip Near/Far

Results so far:

If I configure the Render Settings for the Render Layer (render overrides) as follows, I am able to obtain an RGB, Alpha /w transparency for glass, and a Z-Depth /wo transparency for glass.

> Renderer: Mental Ray

> Image Format: Maya IFF

> Alpha Channel (Mask): Selected

> Depth Channel (Z Depth): Unselected

> Enable Default Light: Unselected

> Associated Render Pass /w Render Layer: Camera Depth Remapped

   Adjust Near/Far clipping planes to match camera

   Adjust Max buffer to 100

> Final Gathering: Selected

> Sampling Mode: Unified

> Quality: 0.5

> Data Type: RGBA (Short) 4x16 Bit

Although I'm obtaining a fairly close result, I'm still missing something.  As per the documentation, I'm experiencing clipping as a result of choosing RGBA (Short) and I'm not able to obtain transparency in the Z-Depth .IFF file.

Ideally, I would much prefer rendering out in OpenEXR - the other layers in the scene are rendering out in OpenEXR RGBA (Half) 4x16 and I'm able to open them in Photoshop CS6 /w an Alpha Channel that includes transparency for the glass ... so all I need now is the Z-Depth pass.

Workflow Question:

What is the proper method of rendering a Z-Depth pass in OpenEXR format that honours transparency (ex: glass), and provides an option to render with/without anti-aliasing.  And, what tool can I use to confirm that the OpenEXR file contains the RGBA/Z information?

I've searched online and found some walk-throughs, forum discussions, and such but most don't cover an OpenEXR workflow.

Advance thanks,

[stumanchu]

Hello, Open EXR is an awesome format...In order to really get a good idea, check out this tutorial....Hope this helps!

http://youtu.be/fQFVYG8kRo0

[hilaire.gagne]

Hi stumanchu,

Appreciate the link; here's a version that offers much more detail in using Maya, AE, and ProEXR:

OpenEXR Workflow in Maya and After Effects CS5
http://www.youtube.com/watch?v=StqSiJ46O4Y

What I'm interested in understanding, is what the proper workflow is in obtaining a Z-Depth pass that honours Transparency and offers the possibility of Anti-Aliasing.  I do have a support ticket open with the fine folks at Autodesk, but if a seasoned professional wishes to jump in and provide some insights on how the pro's do it in the "real world", I'd certainly appreciate it. 

In the interim, here are some links that discusses the challenges as well as some strategies around this ... no indication however as to the correctedness of the workflow in the context of OpenEXR.

Z-Depth /w Transparency
http://asephei.blogspot.ca/2011/10/maya-how-to-manually-generate-custom.html
http://boscripts.blogspot.ca/2010/02/z-depth-with-maya-and-nuke.html

Z-Depth /w Transparency incl. Instancing/Proxy
http://forums.cgsociety.org/showthread.php?f=87&t=941774

I have attached a Maya 2014 SP3 test project that includes some sample geometry (all MIA materials) and configured with Mental Ray.  The layers make extensive use of overrides on materials, render settings, camera, lights, etc. 

Also, the Depth layer in the test file simulates a Z-Depth via Beauty, I have left the Camera Depth Remapped present in the layer for comparison purposes.  The challenge with this approach, as I see it, is that it isn't really providing the Z numerical data which is likely required by AE, Nuke, etc.

Cheers,

[hilaire.gagne]

Posting the response I received from Autodesk Support in case others have the same inquiry:

"... I logged a change request with our development team which has been verified by them as MAYA-#####. The change request is in regards to the transparencies in the depth pass. They have currently set the change request as something they are working to fix in a future release. Unfortunately, I don't have information as to when the fix will come out.

I spoke with other colleagues about your workflow and they told me the same information I had provided you, it is a workaround that may work in most situations, but won't be a perfect solution because the information is not actual data, but instead a representation of the data. The higher the quality the better your results should be. However sometimes you may run into artifacts due to the data translation. I also was not able to find a workaround that is better than the one you have. My colleague who deals with mental ray said there currently is no workaround in mental ray to get transparencies to work.
Like I said though they are looking into fixing the issue in a future release ..."

Here are some links that I compiled during my research in case it's of help to others:

http://asephei.blogspot.ca/2011/10/maya-how-to-manually-generate-custom.html
http://forums.cgsociety.org/showthread.php?f=87&t=941774
http://boscripts.blogspot.ca/2010/02/z-depth-with-maya-and-nuke.html
http://forums.cgsociety.org/showthread.php?t=1027613
http://forums.cgsociety.org/showthread.php?t=134672
http://forums.cgsociety.org/showthread.php?t=1047332
http://wiki.bk.tudelft.nl/toi-pedia/Rendering_with_Render_Layers
http://lipuster.wordpress.com/2011/03/01/the-confusion-called-depth-pass

Cheers,