Installing the plugin
First thing first, we need to install the plugin. I will briefly explain how to do it so there is no problem at all.
It's pretty simple, download the lastest version of CATs plugin using this link to Github.
Now it's time to open Blender.
Select the edit button at the top left of the screen and click on "Preferences"
Requirements and setting up the bones
Right now, you should have your avatar rigged and ready. Remember that eye tracking is completely optional and you should have prepared your avatar for it before hand.
You can get creative with the uses, but for me, I separated the pupils for the actual eyes of the character. It gives a really good overall result.
As I said, do you have you avatar completely rigged? No? Then check out this guide to make the process easier.
How to Rig you Avatar for the Metaverse using Maya LT 3D
If you have everything ready, let's create a new set of bones for the eyes.
Now that you have it set up, mirror the new bones so you have them for both eyes.
Remember to name the bones correctly. Call them Eye_L and Eye_R, so there is no problem when we get to blender and CATS plugin.
Once this is done, now you only need to skin the new bones into the pupil, so it moves along.
Now everyhting is correctly set up. Export the avatar into an fbx and open Blender!
Using the plugin
Now in Blender, import the model we just exported. BUT do not use Blender's own import tool, use instead CATS own import feature.
If you character looks like a complete mess when you imported it, hit the Fix Model button and it should hopefully fix it.
You can use the Testing tab to try out for yourself how it looking so far with the Eye tracking.
Now you can simply export the character.
Setting it up in Unity
This last step is making sure everything works inside Unity! As far as setting up the Avatar inside VRChat, it's the same as always so you can use our guide:
Create and Upload a VRChat Avatar with Blend Shapes Visemes
The only thing we have to keep in mind is to set up the new eyes. Using the Eye Look menu, we can see down below a big sub-menu where we can select both eyes bones.
Once the bones are selected, you can play with each of the 5 different options to make them match their descriptions. Remember that the value you set it up to is the maximum value. That means that the eyes wont move more than that.