Using agent metadatas as xgen custom shader attributes

From Atoms Crowd 3.0, you can control custom xgen shading attributes with agent metadatas.

Create an xgen description
Inside the preview/option tab, go under the "custom shader parameters" area and add an "hair_color" color attribute.
Create a new arnold shader and attach to the color attribute an "aiUsetColorAttribute" node
Set "hair_color" as attribute name on the "aiUsetColorAttribute" node.
Now attach the shader to your xgen description

Create a new atoms scene
Add an "addMetadata" module, then set the metadata name to "xgen_hair_color" and vector as type. Finally assign some random color to the vector value attribute.
If you want to see inside the viewport the color add a "copyMetadata" module and set "xgen_hair_color" as source and "color" as destination, turn on copy and initFrame options. Finally under the settings tab of the agent group turn on the "Use color metadata" option.

Export an atoms cache and a groom cache from your sim.
Create a new atoms proxy node and set up the variation table, the atoms cache and the groom cache
Render your scene with arnold.