Sunday, May 18, 2008

Latest News

I am getting a lot of requests regarding a 64bit version of zDepthDOF. Believe me, I want one too! And I had intended to do one at least for the last two years. Alas, Autodesk is not helping.
Read more about the planned 64bit versions.
In the meantime I intend to re-test and shortly update the system requirements. From the feedback I get it seems zDepthDOF is mostly compatible with current 32bit versions of Maya, including 8.0, 8.5 and 2008 on Windows XP 32bit SP2, Linux as well as Mac OS X PPC and Intel.
But I'd like to verify this myself.
Troubleshooting Tip
I've received a few cries for help recently.
If you are experiencing problems, here's a link to a CGTalk Forum which might hold useful troubleshooting information:
http://forums.cgsociety.org/showthread.php?p=5219380
Thanks to nicodemus3d for starting the thread and special thanks to rachid and leif3d for the troubleshooting tips!

zDepthDOF for Mental Ray

zDepthDOF is a material shader for Mental Ray which renders zDepth images 'ready-to-use' for depth of field simulation. It provides full keyframable focus control inside the animation package.
While zDepthDOF is intended to be used in conjunction with a compositing package, like for example Apple Computer's Shake, Discreet's Combustion or even Adobe's Photoshop CS, the rendered zDepth images can be used 'as is'. There is no longer a need to re-map grayscale values to distances inside the compositing package (which is often difficult guesswork) or let alone keyframe them, as all this can now be done within the 3D environment of the animation package.
For information on how to use zDepth images in Shake to create a depth of field effect click here.
On how to use them in Photoshop CS click here.

zDepth Images

The Problem
 The Solution
zDepth images are poorly suited to simulate depth of field as they merely represent the distance of objects from the camera - expressed in grayscale values betweeen the camera's near and far clipping planes.
Difficult to set objects in mid-distance to be in focus
The zDepth image has to be re-mapped from one grayscale ramp to two ramps expanding in opposite directions. This is a time-consuming manual task during post-processing matching grayscale values to distances.
Settings not independend of camera clipping planes
As the zDepth image is clipped by the camera clipping planes they define the bounding values of the ramp. In order to move the position of these values the camera clipping planes need to be moved - which can result in objects disappearing from the scene.
Depth resolution a limiting factor
As the distance between the camera clipping planes is expressed by (normally) only 256 grayscale values there are issues with the depth resolution not being sufficiently high enough to allow exact positioning of the focus area during re-mapping.
Depth of Field difficult to animate
Moving the near plane, focus center or far plane, widening or shortening the focus range means keyframing the re-mapping of the zDepth image's grayscale ramp. This is a difficult post-production process as these distances cannot be keyframed within the original 3D scene (where they could be measured and set exactly) but only be estimated within a 2D grayscale image.
And all this is likely done by a different person than the original animator requiring further co-ordination efforts.
Only one single zDepth channel
Animation packages supporting zDepth images usually do this via one extra image channel.

zDepthDOF Key Features

Easy setting of distance values
Near Distance, Focus Distance, Focus Range (the area in full focus) and Far Distance can all be set individually allowing animators total control of which object is to be in focus, be it close, in the middle or at the far back of a scene.
Independence of camera clipping planes
Camera near and far clipping planes remain as they are as zDepthDOF uses its own settings. (However, the camera's near and far clipping planes can be used as the near and far distance values.)
Values can be keyframed
The animator can easily move the camera's focus over time. Set it to widen or narrow, come closer toward the camera or move further back.
This no longer needs to be a manual process in post-production.
Values can be dependend on others
Near Distance can be user-specified or set to the camera's near clipping plane.
Far Distance can be user-specified, the camera's far clipping plane, or set to be equal or a multiple of the Near Distance.
Up to 4 different zDepth channels per image
As zDepthDOF renders a separat image and as the colors of its ramp can be set, up to four instances of zDepthDOF can be piped into one final image using the Red, Green, Blue and Alpha channels.
This allows to store up to 4 independently animated focus areas in one image, giving post-production the final decision to choose which object is to be in focus. Post-production merely needs to pick the appropriate image channel for the depth of field blur.
This is a very powerful feature of zDepthDOF.
It also renders faster than 4 individual zDepth channels as object intialization and their movement only needs to be calculated once.
Combined Image
Red Channel
Green Channel
Blue Channel
Alpha Channel
For instructions on how to set up 4 zDepthDOF channels to render into one image click here.
And as each color in zDepthDOF can be a keyframed ramp in itself, several in-focus areas could be created within a scene. The possibilities are almost endless.

Demo

Demo movies are encoded as MPEG4 movies, best viewed with QuickTime.
This demo is a low resolution version - for bandwidth reasons.
A high resolution version is available here (45MB).

1. Create a still image or animation
For this demo the following still image was used:

2. Keyframe Near, Far and Focus Distances and render the scene with zDepthDOF
The result could be a movie like this:
<a href="http://homepage.mac.com/bauer/portfolio_shaders/zDepthDOF/gfx/demo_zDepth.mpg">demo_zDepth.mpg</A>
[Can't see any movie? Download an .avi version from this link (3.2MB).]
In this example the focus is first moved from near to far, and back;
then just the far distance is moved further back, followed by just the near distance.
Both are then moved forward to focus on the center sphere.
The focus area is then expanded from the center to engulf all objects, and back;
followed by a softening of the focus area's fall-off, and finally a crisp fall-off.

3. The resulting Depth of Field animation
The depth of field blur is deliberately exagerated to better demonstrate the effect.
<a href="http://homepage.mac.com/bauer/portfolio_shaders/zDepthDOF/gfx/demo_movie.mpg">demo_movie.mpg</A>
This example also uses the zDepth image to reduce the contrast and saturation of out-of-focus areas (both exagerated for demonstration purposes).
Compositing has been done in Shake.
[Any visible banding when the Depth of Field focus shifts is due to the MPEG compression and the exaggerated contrast shift.]

Installation - Maya

zDepthDOF has been tested to run on these versions of Maya:
- RedHat Linux Enterprise Edition: Maya 6.0, Maya 6.5
- Windows XP Professional 32bit SP2: Maya 6.0, Maya 6.5, Maya 7.0, 2008
- Mac OS X 10.4: Maya 5.0, Maya 6.0, Maya 6.5, Maya 7.0
It is very likely though, that it will work with other versions too.
If your version of Maya is not 6.0 then you will need to adapt the installation instructions below to suit your version's folder path names.

Installation - Maya 6.0 RedHat Linux


It is best if you install zDepthDOF in your local user folder. It's a slightly lengthier process but you do not need admin privileges to install the shader.
Just follow these step by step instructions:

1.
Copy the file 'maya.rayrc' from /usr/aw/maya6.0/mentalray/ to [user_folder]/maya/6.0/prefs/
(Replace '[user_folder]' with the full file path of your local user folder.) This is the Maya preferences file for Mental Ray. At startup Maya looks in your local user folder first to see if a prefs file is present, if so Maya uses it. Otherwise the default 'maya.rayrc' file (from the original location) gets used.

2.
Edit 'maya.rayrc' to e.g. this:
#*****************************************************************************
# Copyright 1986-2003 by mental images GmbH & Co.KG, Fasanenstr. 81, D-10623
# Berlin, Germany. All rights reserved.
#*****************************************************************************
# Evaluated at startup time of the plug-in to fill the mental ray registry.
#*****************************************************************************/

registry "{MAYABASE}" value "/usr/aw/maya/mentalray" end registry
registry "{USER}" value "[user_folder]/maya/6.0/mentalray" end registry

registry "{SYSTEM}" value "irix" end registry
registry "{DSO}" value "so" end registry

$lookup "{MAYABASE}"
$lookup "{SYSTEM}"
$lookup "{DSO}"

registry "{MRMAYA_START}"
link "{MAYABASE}/lib/base.{DSO}"
link "{MAYABASE}/lib/physics.{DSO}"
link "{MAYABASE}/lib/mayabase.{DSO}"
link "{MAYABASE}/lib/contour.{DSO}"
link "{USER}/lib/zDepthDOF.{DSO}"
mi "{MAYABASE}/include/mayabase.mi"
mi "{MAYABASE}/include/base.mi"
mi "{MAYABASE}/include/physics.mi"
mi "{MAYABASE}/include/contour.mi"
mi "{USER}/include/zDepthDOF.mi"
echo "mental ray for Maya - startup done"
end registry

$lookup "{MRMAYA_START}"
This registers the zDepthDOF shader with Mental Ray.
If your 'maya.rayrc' file looks different, especially if it has more 'link' and 'mi' entries, leave them as they are as these are for other shaders previously installed. Important is the addition of the three highlighted lines.

3.
Add this line to the file [user_folder]/maya/6.0/Maya.env (create the file if it isn't already present):
MI_CUSTOM_SHADER_PATH = [user_folder]/maya/6.0/mentalray/include
This tells Mental Ray where to look for custom shaders.

4.
Copy 'zDepthDOF.mi' to [user_folder]/maya/6.0/mentalray/include/
This is the Mental Ray shader description file, containing info about the shader's user variables.

5.
Copy 'zDepthDOF.so' to [user_folder]/maya/6.0/mentalray/lib/
The actual shader DLL.

6.
Copy 'render_zDepthDOF.xpm' to [user_folder]/maya/6.0/prefs/icons/
This is the zDepthDOF icon. It will show up in Maya's Hypershade under 'Create mental ray Nodes' in the bottom section 'Miscellaneous'.

7.
Copy 'AEzDepthDOFTemplate.mel' to [user_folder]/maya/6.0/scripts/
This is the user interface MEL script for zDepthDOF's Attribute Editor settings.

8.
And finally make sure Mental Ray is up and running as zDepthDOF only works with Mental Ray. (It does not work with any other renderers like 'Maya Software' or 'Maya Hardware'.)
To do so, go to Maya's Windows menu -> Settings/Preferences -> Plug-in Manager and ensure 'Mayatomr.lib' is set to 'loaded' and 'auto load'.

Installation - Maya 6.0 Windows XP Professional


Just follow these step by step instructions:

1.
Edit your 'C:\Program Files\Alias\Maya6.0\mentalray\maya.rayrc' file.
For zDepthDOF you need to add one line each at the end of the 'link' and 'mi' entries:
#*****************************************************************************
# Copyright 1986-2003 by mental images GmbH & Co.KG, Fasanenstr. 81, D-10623
# Berlin, Germany. All rights reserved.
#*****************************************************************************
# Evaluated at startup time of the plug-in to fill the mental ray registry.
#*****************************************************************************/

registry "{MAYABASE}" value "[your_maya_application_path]/mentalray" end registry

registry "{SYSTEM}" value "irix" end registry
registry "{DSO}" value "so" end registry

$lookup "{MAYABASE}"
$lookup "{SYSTEM}"
$lookup "{DSO}"

registry "{MRMAYA_START}"
link "{MAYABASE}/lib/base.{DSO}"
link "{MAYABASE}/lib/physics.{DSO}"
link "{MAYABASE}/lib/mayabase.{DSO}"
link "{MAYABASE}/lib/contour.{DSO}"
link "{MAYABASE}/lib/zDepthDOF.{DSO}"
mi "{MAYABASE}/include/mayabase.mi"
mi "{MAYABASE}/include/base.mi"
mi "{MAYABASE}/include/physics.mi"
mi "{MAYABASE}/include/contour.mi"
mi "{MAYABASE}/include/zDepthDOF.mi"
echo "mental ray for Maya - startup done"
end registry

$lookup "{MRMAYA_START}"
This registers the zDepthDOF shader with Mental Ray.
If your 'maya.rayrc' file looks different, especially if it has more 'link' and 'mi' entries, leave them as they are as these are for other shaders previously installed. Important is the addition of the two highlighted lines.

2.
Copy 'zDepthDOF.mi' into folder 'C:\Program Files\Alias\Maya6.0\mentalray\include\'.
This is the Mental Ray shader description file, containing info about the shader's user variables.

3.
Copy 'zDepthDOF.dll' into folder 'C:\Program Files\Alias\Maya6.0\mentalray\lib\'.
The actual shader DLL.

4.
Copy 'render_zDepthDOF.xpm' into folder '%USERPROFILE%\My Documents\maya\6.0\prefs\icons\'.
This is the zDepthDOF icon. It will show up in Maya's Hypershade under 'Create mental ray Nodes' in the bottom section 'Miscellaneous'.

5.
Copy 'AEzDepthDOFTemplate.mel' into folder '%USERPROFILE%\My Documents\maya\6.0\scripts\'.
This is the user interface MEL script for zDepthDOF's Attribute Editor settings.

6.
Make sure Mental Ray is up and running as zDepthDOF is a Mental Ray shader and only works with Mental Ray. (It does not work with any other renderers like 'Maya Software' or 'Maya Hardware'.)
To do so, go to Maya's Windows menu -> Settings/Preferences -> Plug-in Manager and ensure 'Mayatomr.lib' is set to 'loaded' and 'auto load'.

And Finally
There is one potential issue with the latest Microsoft Service Pack which might affect you.
Read about it in Latest Additions.

Installation - Maya 6.0 Mac OS X 10.4



Note
Due to a compiler issue on my PowerBook the Mac version currently compiles to 650K (where it should be no more than 8-10K). I had hoped Mac OS X 10.4 with gcc 4.0 would resolve this, but it didn't. It probably takes a new G5 to get rid of the problem...
zDepthDOF is fully functional on the Mac but due to its size I do not include it in the download files. You can download it from here.


It is best if you install zDepthDOF in your local user folder. It's a slightly lengthier process but you do not need to install files inside the Maya application package, which is never a good idea.
Just follow these step by step instructions:

1.
Copy the file 'maya.rayrc' from /Applications/Alias/maya6.0/Maya/Contents/mentalray/ to [user_folder]/Library/Preferences/Alias/maya/6.0/prefs/
(Replace '[user_folder]' with the full file path of your local user folder, which is typically '/Users/[user_name]'.)
To get to the contents inside the Maya application control-click (or right-click) on its icon and select 'Show Package Contents' from the popup menu.
'maya.rayrc' is the Maya preferences file for Mental Ray. At startup Maya looks in your local user folder first to see if a prefs file is present, if so Maya uses it. Otherwise the default 'maya.rayrc' file (from inside the Maya application package) gets used.

2.
Edit 'maya.rayrc' to e.g. this:
#*****************************************************************************
# Copyright 1986-2003 by mental images GmbH & Co.KG, Fasanenstr. 81, D-10623
# Berlin, Germany. All rights reserved.
#*****************************************************************************
# Evaluated at startup time of the plug-in to fill the mental ray registry.
#*****************************************************************************/

registry "{MAYABASE}" value "/Applications/Alias/maya6.0/Maya.app/Contents/mentalray" end registry
registry "{USER}" value "[user_folder]/Library/Preferences/Alias/maya/6.0/mentalray" end registry

registry "{SYSTEM}" value "irix" end registry
registry "{DSO}" value "so" end registry

$lookup "{MAYABASE}"
$lookup "{SYSTEM}"
$lookup "{DSO}"

registry "{MRMAYA_START}"
link "{MAYABASE}/lib/base.{DSO}"
link "{MAYABASE}/lib/physics.{DSO}"
link "{MAYABASE}/lib/mayabase.{DSO}"
link "{MAYABASE}/lib/contour.{DSO}"
link "{USER}/lib/zDepthDOF.{DSO}"
mi "{MAYABASE}/include/mayabase.mi"
mi "{MAYABASE}/include/base.mi"
mi "{MAYABASE}/include/physics.mi"
mi "{MAYABASE}/include/contour.mi"
mi "{USER}/include/zDepthDOF.mi"
echo "mental ray for Maya - startup done"
end registry

$lookup "{MRMAYA_START}"
This registers the zDepthDOF shader with Mental Ray.
If your 'maya.rayrc' file looks different, especially if it has more 'link' and 'mi' entries, leave them as they are as these are for other shaders previously installed. Important is the addition of the three highlighted lines.

3.
Add this line to the file [user_folder]/Library/Preferences/Alias/maya/6.0/Maya.env (create the file if it isn't already present):
MI_CUSTOM_SHADER_PATH = [user_folder]/Library/Preferences/Alias/maya/6.0/mentalray/include
The text should be all on one line. This tells Mental Ray where to look for custom shaders.

4.
Copy 'zDepthDOF.mi' to [user_folder]/Library/Preferences/Alias/maya/6.0/mentalray/include/
This is the Mental Ray shader description file, containing info about the shader's user variables.

5.
Copy 'zDepthDOF.so' to [user_folder]/Library/Preferences/Alias/maya/6.0/mentalray/lib/
The actual shader DLL.

6.
Copy 'render_zDepthDOF.xpm' to [user_folder]/Library/Preferences/Alias/maya/6.0/prefs/icons/
This is the zDepthDOF icon. It will show up in Maya's Hypershade under 'Create mental ray Nodes' in the bottom section 'Miscellaneous'.

7.
Copy 'AEzDepthDOFTemplate.mel' to [user_folder]/Library/Preferences/Alias/maya/6.0/scripts/
This is the user interface MEL script for zDepthDOF's Attribute Editor settings.

8.
And finally make sure Mental Ray is up and running as zDepthDOF only works with Mental Ray. (It does not work with any other renderers like 'Maya Software' or 'Maya Hardware'.)
To do so, go to Maya's Windows menu -> Settings/Preferences -> Plug-in Manager and ensure 'Mayatomr.lib' is set to 'loaded' and 'auto load'.

Installation - Softimage XSI 4.2 Windows XP Professional

You will need admin access privileges to be able to install the shader. This is because XSI stores the path to a shader's DLL in the Window's Registry, which is only accessible with admin privileges.
If you know of a way to install shaders without the requirement of admin privileges, please drop me an email and tell me!

1.
In XSI go to menu 'File' -> 'Add-On' -> Plugins (SPDL)...

2.
In the new dialog box click the 'Install...' button.

3.
In the following dialog box click the '...' button in the upper right hand corner and navigate to the zDepthDOF folder.

4.
Select the one file available: 'zDepthDOF.spdl' and click 'OK'.
The info field in the dialog box will tell you whether the installation was successful and where the three zDepthDOF files were installed.
They were likely installed in these folders (but your installation may vary):
- zDepthDOF.spdl: [your local 'Softimage' folder]\XSI_4.2\Application\spdl\
- zDepthDOF.dll: [your local 'Softimage' folder]\XSI_4.2\Application\bin\nt-x86\
- zDepthDOF.Preset: [your local Softimage folder]\XSI_4.2\Data\DSPresets\Shaders\Material\
Make a note where the 'zDepthDOF.Preset' was installed as you will need to navigate to this folder when you want to select zDepthDOF as a material shader.

5.
It is a good idea to quit Softimage XSI after the installation and re-launch it before using the shader.
XSI seems to be more stable that way.

Usage & Settings

Maya's Hypershade


In Maya use Hypershade to create a new Surface Shader node.
Select 'Create mental ray Nodes' from the popup menu in the top left corner and open the 'Miscellaneous' section at the bottom. Click the 'zDepthDOF' icon.
In the Work Area middle-mouse-button-drag from the zDepthDOF node onto the Surface Shader node and pipe its outValue into the Surface Shader's outColor.


XSI's Render Tree


In Softimage XSI use Render Tree to add a material shader. One way is via the Render Tree's 'Nodes' menu -> Illumination -> More...
Navigate to the 'zDepthDOF.Preset' file as noted during installation and select it. (Softimage hides the '.Preset' extension 'zDepthDOF'.) As mentioned in the installation instructions it is likely found in [your local Softimage folder]\XSI_4.2\Data\DSPresets\Shaders\Material\.
Pipe it directly into the material's 'Surface' value.



zDepthDOF Settings


Maya 6.0
 Softimage XSI 4.2

Near Distance


Near Distance settings define where the full out-of-focus point for objects close to the camera lies.
In zDepth image terms everything from the camera up to this distance will be rendered fully white, or which ever color is set in the Near Distance 'Color' field.
Near Distance popup menu
- 'Camera Near Clip Plane': the current camera's near clipping plane setting is used as Near Distance.
- 'User-specified Distance': a user-specified value can be set as Near Distance.
Distance
Only available if 'User-specified Distance' is selected from the Near Distance popup menu.
Any number from 0 upwards. Make sure you don't set it to anything higher than the Focus Distance or unexpected results will happen.
If you ever want to set 'Distance' to a value less than 0 rather use the 'Color' field instead and set it to a color less bright than white.
Color
Specifies the color used in the zDepth image for the Near Distance point.
White by default, as needed by Apple's Shake.

Focus Distance


Focus Distance settings define the area where objects are in full focus.
In zDepth image terms everything will be rendered fully black, or which ever color is set in the Focus Distance 'Color' field.
Focus Distance
The distance at which objects are in full focus.
Any number from 0 upwards. But make sure you set it to a value between 'Near Distance' and 'Far Distance' or unexpected results will happen.
Focus Range
Specifies the width of the full focus area. The Focus Range value is added as well as subtracted from the Focus Distance to define an area in full focus.
Any number from 0 upwards.
Color
Specifies the color used in the zDepth image for objects in full focus.
zDepthDOF creates two color ramps blending from the Focus Distance color in the center to the Near Distance color, and the Far Distance color respectively. Black by default, as needed by Apple's Shake.

Far Distance


Far Distance settings define where the full out-of-focus point for objects furthest away from the camera lies.
In zDepth image terms everything from this distance and further away will be rendered fully white, or which ever color is set in the Far Distance 'Color' field.
Far Distance popup menu
- 'Camera Far Clip Plane': the current camera's far clipping plane setting is used as Far Distance.
- 'Same as Near Distance': sets the distance between Far Distance and Focus Distance to be equal to the distance between Near Distance and Focus Distance. In effect it mirrors the blend from in-focus to out-of-focus on either side of Focus Distance. Takes into account whether Near Distance is set to the camera's near clipping plane or whether it is a user-specified value.
- 'Multiple of Near Distance': sets the distance between Far Distance and Focus Distance to a user-specified multiple of the distance between Near Distance and Focus Distance. Allows to keep the Far Distance in relation to the Near Distance. Takes into account whether Near Distance is set to the camera's near clipping plane or whether it is a user-specified value.
- 'User-specified Distance': a user-specified value can be set as Far Distance.
Multiple
Only available if 'Multiple of Near Distance' is selected from the Far Distance popup menu.
If set to '1' provides the same result as 'Same as Near Distance'.
Any number from 0 upwards. I find a value of '2' works quite well.
Distance
Only available if 'User-specified Distance' is selected from the Far Distance popup menu.
Any number from 0 upwards. Make sure you don't set it to anything lower than the Focus Distance or unexpected results will happen.
Color
Specifies the color used in the zDepth image for the Far Distance point.
White by default, as needed by Apple's Shake.

Other Options


Invert zDepth Image
Provides a quick way to invert the rendered zDepth image.
zDepthDOF's default values are set to work with Apple's Shake, with white representing areas out-of-focus and black areas in focus. If your compositing software requires black and white to be swapped (i.e. black for areas out-of-focus and white for areas in focus) tick this check-box to get the required result.
If you use other colors than grayscale values, this option might not make much sense.

Tips & Tricks

This section explains techniques which might not be obvious right away.
How do I find out exact distances in my scene?
As zDepthDOF requires entry of an exact Focus Distance what is the easiest way to get to that number from within a given 3D szene?
I'm not aware of a similar technique in Softimage XSI, but Maya allows you to display an object's distance from the camera.
From the Display menu select Heads Up Display -> Object Details. This will display a couple of statistics about the selected object, including Distance From Camera.
I find it easiest to use this feature with a locator. Create a locator and in orthographic views position it exactly to where you want your Focus Distance to be, i.e. on top of the object you want in full focus. With the locator still selected switch back to your camera view and note down the exact distance from the camera. This is the value you should enter in zDepthDOF's Focus Distance field.
A locator will also help you determine the Focus Range value, in case you want a wider area to be in full focus - not just the Focus Distance plane. In your scene place the locator to the edge of where you want your full focus area to reach, switch back to your camera and read the Distance From Camera. Subtract this value from the Focus Distance value you noted down earlier and enter this as the Focus Range in zDepthDOF's Focus Range field. Should the number be negative, just omit the minus and use the absolute value.

How do I get everything in full focus from a certain distance onward?
Suppose you only want items in the forground to be blurry, but everything from a certain distance on in full focus all the way to the far back of your scene.
Of course you could set the Far Distance value to a ridiculously high value. But that's not ideal as zDepthDOF will still render a gradient towards that far distance.
It is much better if you set the Far Distance to 'Camera Far Clip Plane' and set the Far Distance Color to be exactly the same as the Focus Distance Color.
That way no matter what gradient zDepthDOF is calculating between your Focus Distance and the camera's far clipping plane, it will in effect end up to be all the same color.
And this means that in your compositing package if you set the Focus Distance Color to not apply any blur, your objects in Focus Distance will be fully sharp as will all other objects into the far distance.

How do I set up 4 different zDepth channels to render into one image?
As mentioned in the Key Features section above, zDepthDOF allows you to render up to 4 completely different zDepth channels into one image. These 4 channels can each be individually animated and set to different focus settings.
The idea is to give post-production the final decision on which object to have in foucs (from a choice of 4).
This is how the nodes can be set up in Maya's Hypershade:
Create one instance each of zDepthDOF for the Red, Green, Blue and Alpha channels.
In these four instances make sure you set the focus colors for the Red instance to be either black or fully red, for the Green instance either black or fully green, for the Blue instance either black or fully blue and for the Alpha instance either black or white.
zDepthDOF_Quad is a simple Maya Surface Shader node.
mib_color_mix is a Mental Ray Data Conversion node with the following settings:
specify one of the Red, Green or Blue instances' Out Color to be the 'Color_base' and the other two to be 'Color_0' and 'Color_1'. Add the three colors together by setting 'Num' to 2 and 'Mode_0' and 'Mode_1' to 2 as well, which is the color add mix.
Pipe the mib_color_mix's Out Color into the Surface Shaders's color node. In above picture you can see how to pipe the Alpha instance into the Surface Shader as well.
You can now animate and set depth values individually for each of the four instances of zDepthDOF, yet all four will render into a single image. In your compositing package simply select then which image channel you want to use for the depth of field blur.

How do I use transparency with zDepthDOF?
zDepthDOF verison 1.6 adds support for fully transparent elements. This is helpful when you want to use an image file as an alpha to create a 'paper cut-out' effect. For example when you're using sprites on particles.
A normal Mental Ray zDepth image will show just your image planes and disregard any alpha. zDepthDOF however can use transparency.
Mental Ray zDepth image
 zDepthDOF
There are two ways of setting up the Hypershade network in Maya: the nice and easy way, or the recommended way.
Let's start with the nice and easy one:
Use a simple lambert node and pipe the zDepthDOF node's 'outValue' into the lambert's 'color'.
Then pipe the 'outColor' of an image file, or as in this case a checkerboard pattern, into the 'transparency' node of the lambert.
Finally set the lambert's 'Ambient Color' to 1 and its 'Diffuse', 'Translucence', 'Translucence Depth' and 'Translucence Focus' all to 0.
Apart from easier setup, the advantage is that the rendered image will have a useful alpha channel as well.
[Thanks Vincent for the tip!]
However, the recommended node for a shader that doesn't use lights, like zDepthDOF which only uses depth information, is a surface shader node.
See which version works best for you. I merely want to present both so you can choose.
The recommended way:
On the left side is your image file with the alpha map, in my case 'file_Saturn'. On the right a surface shader node, I called mine 'zDetphDOF_Stencil'.
The image file provides the transparency so its 'outColor' value is piped into the 'outTransparency' value of the surface shader. If, as in my case, you want black to be fully transparent and white to be opaque you need to invert the image via a 'Reverse' node in-between.
zDepthDOF is introduced via a 'blendColors' node. Pipe the zDepthDOF node's 'outValue' into 'color1' of the blendColors node. In the attribute editor set 'Color 2' to black (not shown here).
And finally, to blend depending on the image file, pipe the file's 'outColorR' value into the 'blender' value of the 'blendColors' node. As the blender value is only a single value you cannot pipe in the image's full color. But any of the Red, Green or Blue components will do, provided your image is a grayscale image. I used the Red component.
The network is similar if you want to set up a checkerboard pattern with one of the squares being a 'transparent' color. Just use a checkerboard node instead of the image file:

How can I use zDepth images with Photoshop CS?
If you don't have access to a compositing package like Shake or if you mostly work with still images you can also use Photoshop to apply a depth of field blur from zDepth images.
Photoshop CS (Photoshop verson 8.0 or later) comes with a Lens Blur filter that provides the required functionality. With probably even more control than Shake's iBlur node.
1.
Copy the zDepth image renderd with zDepthDOF into a new channel of your image (not a new layer!).

2.
Select menu 'Filter' -> Blur -> Lens Blur.
In the 'Depth Map' section select the channel you just added from the popup menu.
Leave the 'Blur Focal Distance' at 0.

In the 'Iris' section select a 'Radius' and 'Shape' to apply the depth of field blur.

Creating a Depth of Field Effect in Shake

With a normal zDepth image you would likely use ZDefocus.
Yet with an image created by zDepthDOF you would simply use iBlur from the 'Filter' tab:
xPixels and yPixels specify the amount of blur applied to fully white pixels. 80, as in my example, is probably too high. This value was just used for demonstration purposes.
controlChannel specifies which channel of the zDepth image is used for the blur effect. As zDepthDOF renders a grayscale image by default (unless you specify otherwise) you can pick any of the Red, Green or Blue channels. I used the Red channel.

If you want a more realistic depth of field effect you should also reduce contrast and saturation for areas out of focus. You can use the zDepth image to do this as well:
A Reorder node is used to move either the Red, Green or Blue channel into the Alpha channel as both Saturation and ContrastLum are driven by the Alpha channel.

Latest Additions to zDepthDOF

Version 1.6 - Support for full transparency
6. April 2005
zDepthDOF now supports the use of an image file as an alpha to create 'cut out' stencil effects. Full transparency could also be applied to e.g. a checkerboard pattern where one square uses a 'transparent' color.
However, any transparency value other than 0% or 100% will give arbitrary results as blending color ramps and distances doesn't really match. It might still work for you in some cases, it might give you funky cool results - or it might just be plain useless. See how it works for you. If not stick to either full transparency or no transparency.
For information on how to set up a shading network in Maya's Hypershade that makes use of transparency click here. The setup is pretty similar for XSI.
Please note:
zDepthDOF does not support reflections at the moment. It's a similar issue as color values returned do not necessarily represent proper depth information. Only that the issue gets aggravated with recursive reflections.

Info for Windows Users - 'Mental Ray aborted...' Error
20. April 2006
There is one potential issue with the latest Windows Service Pack. To make a long story short zDepthDOF needs the 'msvcr70.dll' runtime library usually found in the 'C:\WINDOWS\system32' folder.
This library has been distributed by Microsoft in the past as a shared system component but the lastest Service Pack seems to delete it. You can read more about the technical details on the Microsoft website.
If you are experiencing an error message saying 'Mental Ray aborted...' when using zDepthDOF then you are possibly missing that library.
Check the 'C:\WINDOWS\system32' folder to see if a file 'msvcr70.dll' exists. If not reinstall it from your Windows Installation CD or download a copy from www.dll-files.com. Drop it into 'C:\WINDOWS\system32' and zDepthDOF will be working fine again.
Alternatively you should be able to put 'msvcr70.dll' in the same folder as the 'zDepthDOF.dll', e.g. 'C:\Program Files\Alias\Maya6.0\mentalray\lib\' for Maya 6.0.

System Requirements

zDepthDOF is available for and has been tested with:
Alias Maya
- RedHat Linux Enterprise Edition: Maya 6.0, 6.5
- Windows XP Professional 32bit SP2: Maya 6.0, 6.5, 7.0, 2008
- Mac OS X 10.4: Maya 5.0, 6.0, 6.5, 7.0

Softimage|XSI
- Windows XP Professional 32bit SP2: XSI 4.2

It is very likely though, that zDepthDOF will also work with other versions of Maya or XSI.

What about a 64bit version?
Let me assure you, I fully intend to offer a 64bit version of zDepthDOF. At least for Maya.
Please let me know if you are interested in a 64bit version for XSI as I am currently not sure it is worth offering one.
I own Mental Ray 3.6, the only puzzle piece missing is Maya itself! I develop mainly on Mac OS X and to this day (May 18th 2008) Autodesk still has not delivered a 64bit version of Maya for Macintosh - while a Windows and Linux version have been out for ages. Perhaps at SIGGRAPH 2008. Finger's crossed...
If you want a 64bit version of zDepthDOF please let Autodesk know that they should offer a 64bit version of Maya for Macintosh. Until that is happening I'm afraid there won't be a 64bit version of zDepthDOF. Blame Autodesk.

Download

Alias Maya
zDepthDOF has been tested to run on these versions of Maya:
- RedHat Linux Enterprise Edition: Maya 6.0, 6.5
- Windows XP Professional 32bit SP2: Maya 6.0, 6.5, 7.0, 2008
- Mac OS X 10.4: Maya 5.0, 6.0, 6.5, 7.0
It is very likely that it will work with other versions too. There is one potential issue with the latest Microsoft Service Pack, however. For more info see Latest Additions.

Softimage|XSI
- Windows XP Professional 32bit SP2: XSI 4.2

3ds max
- Windows XP Professional 32bit SP2: 3ds max 7
Robert Langnickel of Titanfilm thankfully adapted the .mi file so that zDepthDOF can be made to run with 3ds max.
Matt Dignam of Twitch Studios thankfully provided installation instructions for 3ds max 7. Check out the ReadMe.txt in the .zip archive.
If you have version 6 of 3ds max the shader might work for you too, but you will likely need to adapt the instructions to suit your version.
As I don't have access to 3ds max I am unfortunately unable to support this version.
The files are hosted as a service to the 3ds max community only.
If you know what to do and if it works for you, great! If not, I'm afraid I cannot help, sorry. The files are provided 'as is'.

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