3D Channel effects

Third-party effects in this category included with After Effects:

• EXtractoR effect

• IDentifier effect

• ID Matte

See Third-party plug-ins included with After Effects.

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.

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.

Using channels in OpenEXR files

3D Channel effects can use 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.

ProEXR plug-ins, IDentifier, and EXtractoR

The EXtractoR and IDentifier plug-ins from fnord software are included with After Effects to provide access to multiple layers and channels of OpenEXR files.

Documentation for fnord ProEXR plug-ins is available in a PDF document on the fnord software website, which includes links to a sample multi-channel EXR file and an After Effects project that uses it. The instructions in the fnord document regarding the removal of the OpenEXR plug-ins don’t apply to After Effects CS5.

3D Channel Extract effect

The 3D Channel Extract effect makes auxiliary channels visible as either grayscale or multichannel color images. You can then use the resulting layer as a control layer for other effects. For example, extract the depth information in a 3D channel image file and then use it as an influence map in the Particle Playground effect, or extract values from the unclamped RGB channel to produce a matte that generates glowing highlights.

This effect works with 8-bpc and 32-bpc color.

The value that is mapped to white or black.

The channel to extract from the 3D image:

Represents the distance of a given shaded pixel from the camera. White represents the greatest distance; black pixels are closest to the camera. Effects such as the Lens Blur effect can use this information to generate depth-of-field effects. When you apply the channel directly as a luma matte, you get fog.

Work with the anti-alias parameter

The Anti-alias parameter allows you to choose whether the output of the effect is anti-aliased or not. Anti-aliased depth passes are useful to smooth the edges of mattes used for depth compositing or color correction.

Disable this option when you use Depth of Field or other effects where it is important that objects and their edges are considered to be at the same distance. Anti-aliased edges affect the gray values of the edge pixels, which can affect the apparent depth of the edge and cause artifacts in the effect using the matte.

Clamp Output Available in 32-bpc color mode only, clamps the grayscale output of the effect to values between 0 and 1.0. On by default.

Invert Depth Map inverts the grayscale output of the effect.

Each object can be assigned a separate ID value in the 3D application. You can use a map generated using this channel to selectively apply effects to certain objects in a 3D scene—for example, to apply selective color adjustments. This channel is not anti-aliased.

This channel contains the mapping coordinates of the textures of your object, mapped to the red and green channels. This channel is not anti-aliased.

This channel can be used to check your UV maps or as input for the Displacement Map effect.

This channel maps the direction vector of each point on the surface of an object to the RGB channels. The vectors are relative to the camera. Third-party plug-ins can use this channel as the basis for dynamic relighting and relief rendering. This channel is anti-aliased.

The behavior for this channel varies for various 3D applications. It is used to mark areas near the edges and contours of objects to provide information about their anti-aliasing and overlap behavior.

This channel contains all RGB pixel values of the background without any foreground objects. It is mostly used to store dynamic environmental effects unique to 3D programs such as skies or backgrounds generated from procedural textures. This channel is anti-aliased.

This channel contains the colors from the 3D application as they were presented to the 3D application’s renderer before it applied exposure and gamma adjustments. This channel is anti-aliased.

Each material can be assigned a separate ID value in the 3D application. You can use a map generated using this channel to selectively apply effects to certain materials in a 3D scene. This channel is not anti-aliased.

Depth Matte effect

The Depth Matte effect reads the depth information in a 3D image and slices the image anywhere along the z-axis. For example, you can remove a background in a 3D scene, or you can insert objects into a 3D scene.  

This effect works with 8-bpc, 16-bpc, and 32-bpc color.

The z-axis value at which to slice the image. Everything with a depth value less than this Depth value is matted out.

The amount of feather along the edges of the matte.

Select to matte out everything with a depth greater than the Depth value. Deselect to matte out everything with a depth less than the Depth value.

Depth Of Field effect

The Depth Of Field effect simulates a camera that’s focusing at one depth (focal plane) in a 3D scene, blurring objects at other depths. This effect uses the depth information from the auxiliary channel of an imported file representing a 3D scene. To use the depth information that After Effects calculates for a camera layer, see Create a camera layer and change camera settings.

This effect works with 8-bpc, 16-bpc, and 32-bpc color.

The distance along the z-axis of the focal plane from the camera.

How much blur is applied to objects outside the focal plane.

Determines what depths are in focus on either side of the focal plane.

The higher the value, the more quickly elements drop out of focus with increasing distance from the focal plane.

Dave Scotland provides a video tutorial on the CG Swot website in which he shows how to use the Depth Of Field effect, even with a 3D file that has been rendered without optimal depth settings.

Fog 3D effect

The Fog 3D effect simulates fog by behaving as though a scattering medium is in the air that makes objects look more diffuse as they get more distant along the z-axis.

This effect works with 8-bpc, 16-bpc, and 32-bpc color.

Where along the z-axis the diffuse scattering begins.

Where along the z-axis the diffusion reaches its maximum.

Determines how quickly the scattering occurs. The higher the value, the more dense the fog appears from its starting point.

Creates a foggy background (default). Deselect to create transparency at the back of the 3D scene for compositing on top of another layer.

(Optional) A grayscale layer to use as a control layer, the luminance values of which apply to fog density. For example, use the Turbulent Noise effect to create a swirling control layer for atmospheric fog. Make sure that the dimensions of the gradient layer are at least as great as the dimensions of the 3D scene layer.

How much the gradient layer affects the fog density.

Depth passes for 3D compositions

A depth pass is black and white information that correlates to distance. For example, if you have a scene that is filled with black fog and white objects, the objects that are farther away from the camera have a darker tone than the ones that are closer.

You can extract Z-depth by the 3D channel effects from a nested composition that contains 3D layers. You can use this to apply 3D depth effects to the composition layer, such as a depth of field blur, or to generate a matte for depth compositing or color correction.

Depth passes work with either the Classic 3D or CINEMA 4D composition renderers.

The following 3D channel effects can extract Z-depth from a nested 3D composition:

• 3D Channel Extract
• Depth Matte
• Depth of Field
• Fog 3D

Extract a depth pass

To extract a depth pass, from the Effects panel, apply the 3D Channel Extract effect to a nested composition layer.

Note the following:

• The 3D Channel parameter is disabled when 3D Channel Extract is applied to a nested composition layer.
• Use the Black Point and White Point properties to set the start and end of the depth range. The start and end is measured in pixels from the camera position.
• The default Black Point and White Point values are 5000.0 and 0.0, respectively. If your 3D scene extends farther than 5000 pixels away from the camera you need to increase the Black Point value.
• When the project is set to 32-bpc, the depth output is clamped to 0-1 for the same range that is clamped for 8- or 16-bpc.

Use the EXtractoR effect to extract a depth pass

You can use the EXtractoR effect to extract a depth pass from a nested composition, but anti-aliased edges against a transparent background can render with a fringe.

To view the edges, use the following steps:

ID Matte effect

Many 3D programs tag each element in a scene with a unique Object ID. The ID Matte effect uses this information to create a matte that excludes everything in the scene except the element you want.

This effect works with 8-bpc, 16-bpc, and 32-bpc color.

Isolate elements based on Object ID or Material ID.

The ID value for an object.

The amount of feather along the edges of the matte.

Inverts the selection. Select to matte out the object specified by ID Selection. Deselect to matte out everything but the object (default).

Creates a cleaner matte by removing the colors stored behind the object from the pixels along the edge of the matte. This option works only if the 3D image contains a coverage channel that stores information about the colors behind objects.