Note: All information on this page is based on the 2012 Extension 1 release.
The ZDepth render pass have for goal to provide for each pixels the relative distance of each objects in the scene to the camera that was used to perform the rendering. This information is stored in the render pass as a luminance value creating a grey scale representation of the scene. ZDepth range can be exposed in different ways in terms of color value range and file format bit depth, but floating point file format(16bit or 32bit) offer much more precision. The most common format are usually refered as White is Near and White is Far.
White is Near
This ZDepth render format essentially means that white colour is used to represent object right at the camera level and further away they get, darker colour up to black is used to represent them. Usually this format is normalized and the camera position will be represented by a white value of 1.0(for 16 or 32 bit file format) and black of 0 would be the further away object could be based on the camera Near and Far value.
White is Far
This ZDepth render format is more common and used for example by Maya Mental Ray or Flame/Smoke Action render engine. In this case Black colour value represent object right at the camera level and further away they get, lighter colour is used to represent them. Two format here are quite common here: Normalized and Absolute. Absolute is normally what you will get from renderer like Mental Ray when using OpenEXR as rendering file format. What this means is that white value aren't cliped at 1.0 and colour value are actually representing real scene scale metrics resulting in huge luminance colour range. Normalized is what is used by the Action render engine. In this case the camera Near and Far value are map to 0 and 1 colour value where and black at 0 represent the Near clipping plane and a white at 1.0 represent the Far clipping plane.
How do I know what ZDepth format I'm dealing with?
Where do I get ZDepth render pass?
What can I do with a Zdepth render pass?
Depth Of Field:
This module and Batch node allow to create depth of field effect based on the ZDepth input information. Due to the algorithm use you are required to use ZDepth information contains in between 0 and 1.0. You can use the Depth O Gram Offset and Scale parameters to bring into this range the required depth information to perform the desired effect.
This Matchbox preset allows to create volumetric rays in your scene base on the ZDepth input information.
This Matchbox preset allows to create glowing effect in your scene base on the ZDepth input information.
This Matchbox preset allows to integrate fog type of effect in your scene base on the ZDepth input information.
This Matchbox preset allows to integrate a video input using it's matte into a scene base on it's ZDepth information. This could be use for example to integrate a text element or a logo anywhere into a rendered scene. This preset also allow to create a new ZDepth pass base on the integration, so it could be further used for other ZDepth effect type.
This Matchbox preset allows to extract a matte from a ZDepth input information. This could be used for example separate object from a rendered scene for further processing.
The 3D Blur Batch node allows to create depth of field effect based on ZDepth input information.
What problems can I encounter with ZDepth render pass?