The 3D Channel effects work on 2D layers—specifically,
2D layers with 3D information in auxiliary channels. The sources
of these 2D layers are image sequences that represent 3D scenes
that have been rendered out of a 3D application.
Use 3D Channel effects to integrate 3D scenes into 2D composites
and to modify those 3D scenes. You can import 3D image files saved
in RLA, RPF, Softimage PIC/ZPIC, and Electric Image EI/EIZ formats.
For PIC and EI files, the 3D channel information is in the ZPIC
and EIZ files, respectively. You don’t import ZPIC and EIZ files,
but as long as they’re in the same folder with the PIC and EI files,
you have access to their 3D channels using the 3D Channel effects.
The 3D Channel effects don’t affect other types of files.
3D Channel effects read and manipulate the additional channels
of information, including z-depth, surface normals, object ID, texture
coordinates, background color, unclamped RGB, and material ID. You
can layer 3D elements along the z axis, insert other elements in
a 3D scene, blur areas in a 3D scene, isolate 3D elements, apply
a foggy effect with depth, and extract 3D channel information for
use as parameters in other effects.
If you convert a layer with a 3D Channel effect to 3D and view
the layer from anywhere but the front and center, it doesn’t appear
as expected.
To display depth and other channel values for
a pixel in the Info panel, apply a 3D Channel effect, and then—with
the effect selected—click the pixel in the Composition panel or
Layer panel using the Selection tool.
Lutz Albrecht provides a two-part document on the Adobe website about integrating 3D
applications with After Effects. These articles cover the creation
of UV maps, mattes, and channels from various 3D applications, including
Maxon Cinema 4D, NewTek Lightwave, and Luxology modo. The articles
then show you how to use RE:Vision Effects RE:Map and fnord ProEXR
plug-ins to use that data in After Effects.
Dave Scotland provides a pair of tutorials on the CG Swot website
in which he demonstrates how to create RPF files in a 3D application
and how to use RPF files in After Effects. The first part explains the RPF format
and how to create RPF files in 3DS Max. The second part shows how to use the Object
ID and Z depth information in an RPF file within After Effects,
using the ID Matte, Depth of Field, Depth Matte, and Fog 3D effects.
Chris & Trish Meyer give tips on using the 3D Channel effects
in an article on the ProVideo Coalition website.
Using channels in OpenEXR files
3D Channel effects can make use of the channels in OpenEXR
files—such as a depth channel—if the channels have been tagged.
Unlike some other formats, like RPF, in which a specific set of
channels is defined to always represent specific properties of a
scene, the OpenEXR format is an arbitrary collection of channels with
no inherent meaning. The R, G, B, and A channels are reserved to
represent red, green, blue, and alpha values, but other channels
can be used for any other characteristics. To map channel names
to the values of a specific type for use by other effects, you can
use a file with the name OpenEXR_channel_map.txt. If this file is
in the same folder as the OpenEXR format plug-in, the OpenEXR plug-in
will use the information in this file to tag channels when it imports
an OpenEXR file.
An OpenEXR_channel_map.txt file is not included with After Effects,
but you can download one as part of the ProEXR package from the fnord
software website. The sample OpenEXR_channel_map.txt file
available from the fnord software website includes documentation
describing its use.
The ProEXR package from the fnord software website also includes
the ProEXR Comp Creator plug-in. This plug-in can create a layer
from each of the channels of an OpenEXR file. For example, the layers
can represent the output from a set of render passes from a 3D application.
