# KB00006 - Introduction to Auxiliary Channels in eyeon Fusion
Instructor : Pradeep Mamgain
Today most of the 3d applications produce variety of channels along with traditional RGBA, that is Red, Green, Blue and Alpha channels for transparency. Several high end 3d programs are capable of embedding more channel information in an image that is used by compositors to get more control over the project. They can perform depth based composting using the tools that falls under Deep Pixel Category of tools. Auxiliary channels can store depth of the scene, uv coordinates information, normal orientation information and camera information.
# Auxiliary Channels that Fusion Supports
+ Z-Buffer : It contains a floating point value in each pixel that decides the relative depth of that pixel in the channel.
+ Z-Coverage : You can consider it as extended Z-Buffer. It is used find pixels in Z-Buffer channel that contains more than one object.
+ Background RGBA : This channel is used to find color values from the objects behind the pixel described in the Z-Coverage.
+ Object ID/Material ID: Few 3D applications are capable of storing object id and material id channels. Each pixel in that channel will be identified by that id. It make life easier as we can generate mask and matte based on that information.
+ UV Texture Channels : These are used when you want to wrap a texture around an object. This channel stores mapping coordinate information of each pixel.
+ XYZ Normal Channels: This channel contains about the orientation of each pixel in 3D space. X represents horizontal component of the pixel while X and Z represents vertical and perpendicular component.
We will cover these channels one at a time in near future.
# Fusion Depth Tools
Fusion has four tools that can perform depth based composting. Depth Blur tool is used to blur an image. This tool uses Z-Buffer depth information from the image. Fog Tool also uses Z-Buffer channel to simulate the fog effect. Texture tool is used to replace the texture of any specific objects. Some 3D applications store object ID and material ID info in channels. This tool can utilize that information.It uses the UVW coordinates and XYZ normal channels. You can change lighting in your scene without making any change in the lighting setup inside 3d application. It is true, shader does that inside Fusion. It uses UV coordinate channels and XYZ normal channel to change lighting of the scene. Sometime when you composite 3D elements with live footage, this tool is very handy in that situation to make life easier. These are the four tools that specifically use auxiliary channel data in Fusion.There are four other Fusion tools that are capable of performing operations on auxiliary channels.
Channel Boolean + Auto Gain + Shadow + Luma Keyer
#Image formats that supports Auxiliary Channels
+ Wavefront RLA [.rla]+ 3DS Max RLA [.rla]
+ 3DS Max RPF [.rpf]
+ Maya IFF [.iff]
+ Softimage PIC [.pic, .zpic, .z]
+ OpenEXR [.exr]
#Other Info
# eyeon Fusion KB # Adobe After Effects KB # Autodesk Maya KB # Channel Boolean Tool # Simulating Fog