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How to convert avatars for VRChat to VRM so they can be used with cluster

こはだ

Hello, this is Kohada.

Recently, I’ve been hearing a lot of talk about cluster users wanting to try out VRChat and VRChat users wanting to visit cluster.

One of the biggest hurdles is transferring their usual avatars between platforms. I’ve seen several acquaintances struggle with this, so I’ve decided to explain how to convert a VRChat avatar to the VRM format for use in cluster.

While this guide focuses on using the avatar in cluster, VRM format is widely adopted by various applications, so converting to VRM expands the versatility of your avatar.

Check Avatar Restrictions and Terms of Use

Some avatars have restrictions on modifications and usage. Additionally, follow any specific SDK or Unity version requirements for VRChat. Since we are modifying a VRChat avatar, avoid contacting the creator about unexpected uses like VRM conversion.

Using the "Lucifer" Avatar by Nafunado

For this guide, I'll use the "Lucifer" avatar by Nafunado, which utilizes the common "Marubody" base, making it easier to create new outfits and swap costumes in the future.

Overview of Steps

Avatars compatible with cluster are in VRM 0.x format. Since VRChat avatars are in .fbx format, the steps are as follows:

  • Convert the avatar to VRM format in Unity and input metadata.

  • Adjust jiggle physics.

  • Change shaders.

  • Set up expressions for emotes.

For detailed restrictions on avatars in cluster, refer to the following link.

Create a Unity Project

Start by creating a new Unity project using Unity Hub. Since there are no specific version requirements for the model, I used the recommended version for cluster. Name your project accordingly and choose "3D Core".

The following screenshots are based on Unity version 2021.3.4f1. Interfaces might differ slightly depending on your Unity version.

Install the VRM Conversion Tool

Once the project is created, install the tool for converting to VRM.

Download the "VRM Converter for VRChat" from the link above. This package includes the necessary UniVRM, so it's sufficient for our needs.

Extract the downloaded Zip file and drag the "VRM Converter for VRChat Installer.unitypackage" into the Unity Asset area.

Click the "Import" button in the dialog that appears.

Upon nearing completion of the import, click "Close".

and then click "Use recommended Linear" to change the project's Color Space. Cluster uses Linear Color Space.

If installed correctly, the Unity menu will have new "UniGLTF" and "VRM0" items.

Supplementary Note

Currently, "VRChat Creator Companion" (commonly known as VCC) is used for managing project files of VRChat avatars. If you're using VCC, adding the project as a community repository may simplify installation and make version management easier!

For more details, please refer to the application introduction page on Booth mentioned above.

Install the Original Shader

Next, install the shader recommended for the avatar to check its original colors before switching to MToon for VRM compatibility.

The shader used for this model is as follows.

Download and import the shader similarly as before.

Import Avatar Data

Now, import the avatar data you obtained earlier into Unity. Typically, avatars are provided in .unitypackage format. Import it as done previously.

Drag and drop the avatar data from the Prefab folder into the Hierarchy panel.
Successfully imported.

Remove VRChat Scripts

The avatar data includes VRChat-specific scripts. Remove these before converting to VRM. However, keep a copy of the original Prefab in the same scene for reference, especially for Phys Bone and Phys Bone Collider objects.

Remove these two components from the Inspector of the avatar Prefab.

Convert Avatar to VRM Format

Now, let's convert the avatar to VRM format. Instead of using "Export VRM file from VRChat avatar," directly execute "Export to VRM 0.x." This avoids issues with Spring Bone settings that sometimes occur.

This is because there have been numerous cases where the Spring Bone settings were completely messed up during the export process. Therefore, I will take a slightly more roundabout approach with more manual steps to ensure proper migration.

Drag and drop the avatar Prefab from the Hierarchy panel into the "ExportRoot" at the top left. This will bring up a dialog for metadata (data about the data), where three errors will be displayed.

Title, Version, and Author are required fields.

You can scroll down in this dialog. Enter the "Title" (avatar's name), "Version," and "Author" (creator) for the VRM data of this avatar. These three fields must be filled in; otherwise, the data cannot be exported. "Contact Information" and "Reference" (original work) can be left blank. Select the "Permission Scope for the Avatar's Personality" based on the avatar's terms of use.

Once you've finished entering the information, click "Export" at the bottom right. Set an appropriate location to save the file and click "Save." (I create a folder named "Model" under the Asset folder of the same Unity project, and within that, a folder named after the avatar, where I store the files.)

Load the VRM Avatar

Disable the original avatar Prefab by unchecking the box next to its name in the Inspector. Drag and drop the newly exported VRM avatar into the Hierarchy. Name it appropriately to distinguish it.

Since the shader has changed, the colors are slightly different from before.


Now, the real work begins. From here on, we will:

  • Adjust jiggle physics

  • Change shaders

  • Register expressions

Adjust Jiggle Physics

Now, this is where it gets tricky. VRChat avatars use "Dynamic Bone" and "Phys Bone" systems to make hair, skirts, etc., flutter, but these are not supported in the VRM format.

Therefore, we will use the "Spring Bone" component, which is compatible with the VRM format, to recreate this effect. This Spring Bone component is found within the "secondary" section of the VRM avatar object.

When it comes to jiggle physics in VRM, it's all about the "secondary"!

Click on the "secondary" object and, in the Inspector on the right, add the "VRM Spring Bone" component by clicking "Add Component."

Search for "VRM" or "Spring" and it should appear quickly.

Within this component, you will:

  • Specify the root of the bones to be affected (Root).

  • Set the strength of the spring (Stiffness Force), the strength of gravity (Gravity Power), the direction of gravity (Gravity Dir), and the resistance (Drag Force).

  • Set the colliders that the jiggle physics will interact with.

Note: You don't need to add a "VRM Spring Bone" component for each root bone. Group bones with the same body part, jiggle behavior, and colliders together under one component.

Finding the Root Bones

There are several methods to find the root bones:

1) In a project with the VRC SDK3 Avatar installed, open the Armature of the avatar and look for objects with Phys Bone attached. Note: Since the VRC SDK cannot be downloaded standalone anymore, you need to create a project and import the avatar using the "VRChat Creator Companion."

If the above method is cumbersome, try:

2) Look for bones in the Armature with names that are not defined in the Humanoid format (e.g., Hair, Skirt, Chain—names that suggest they might jiggle).

3) Look for objects typically set up for jiggle physics (e.g., Breast).

4) Look for objects named with xxxx_Root or similar.

These methods might not cover everything! You'll need to process and test the movements, and adjust as needed if something feels off. Alternatively, executing "Export VRM file from VRChat avatar" from the VRM0 menu can bring in all jiggle objects, which can also be used as a reference.

Expand the Armature and add all suspicious bones in groups to the Spring Bone component elements. For this guide, I added the following bones from the Lucifer model to the Root Bone elements of the Spring Bone:

Click the triangle next to "Root Bones" within the component to expand it, and click the "+" button at the bottom right to add as many input fields as needed.

  • Belt_01

  • Chain_01

  • Skirt_Root

  • Breast_L

  • Breast_R

  • Front_Hair*_01 (3 in total)

  • LeftSide_Hair*_01 (2 in total)

  • Ponytail_01

  • RightSide_Hair*_01 (2 in total)

  • Tie_01

For example, for hair, the component would look like this (we will adjust the jiggle parameters later!).

I group them into the same component if they have the same jiggle behavior.
After setting all the jiggle elements and turning on Gizmos, it looks like this.


Setting Up Colliders

Next, we will set up the colliders that the jiggle elements will collide with.

To find the colliders, expand the Armature and look for objects named something like "xxxxCollider" directly under the Humanoid bones. Additionally, inspect each object within the Armature of the pre-VRM conversion avatar to see if it has VRChat-specific scripts (like VRC Phys Bone Collider) attached. These will be the targets for collider settings.

For example, like this. It may not always be a collider, but you can identify it for sure if you have the VRC SDK installed!

Select the object to which you want to add a collider. In the Inspector, click "Add Component" and add "VRM Spring Bone Collider Group."

Colliders should be attached directly to the object, not to the secondary.

For the Lucifer model, I will set the colliders as follows:

  • Head_Collider: Prevents front hair from clipping into the head

  • PlaneCollider_Hair1: Prevents ponytail from clipping into the back

  • PlaneCollider_HairSide: Prevents side hair from clipping into the chest

  • PlaneCollider_Hair2: Prevents the end of the ponytail from clipping into the waist

  • Belt_Collider: Prevents the end of the belt from clipping into the waist

  • Hips: Prevents the skirt from clipping into the navel

  • Upper_Leg_L: Prevents the skirt from clipping into the left thigh

  • Upper_Leg_R: Prevents the skirt from clipping into the right thigh

One issue to note is that VRChat's Phys Bone Colliders offer three shapes: Sphere, Capsule, and Plane. In contrast, Spring Bone only supports spherical colliders.

Since you cannot create identical shapes, you will need to approximate by placing similar colliders.

It's recommended to add new colliders in addition to the original ones. If there are gaps between spherical colliders, clipping may occur, so add colliders as needed.

With Spring Bone, you can only approximate by connecting spheres.
Here's what the colliders look like when set up! (purple spheres)

Reopen "secondary" and set up the collider groups for each Spring Bone component.

  • Belt_01: Belt_Collider

  • Skirt_Root: Hips, Upper_Leg_L, Upper_Leg_R

  • Hair elements: PlaneCollider_Hair1, PlaneCollider_HairSide, PlaneCollider_Hair2

Specify these in the Collider Groups section.

Once this is done, press the play button in Unity to enter play mode. Switch to the "Scene" tab, and move or rotate the Armature objects in the Hierarchy to check for any "floating" or "clipping" issues, and make adjustments accordingly.

For example:

Side hair slightly floating above the chest.
The skirt clipping through the thigh at certain angles.

Addressing "Floating" Issues:

  • Make the collider smaller

  • Increase the distance between the collider and the jiggle object

  • Decrease the "Hit Radius" value in the Spring Bone component

Addressing "Clipping" Issues:

  • Make the collider larger

  • Increase the number of colliders to fill gaps

  • Reduce the distance between the collider and the jiggle object

  • Increase the "Hit Radius" value in the Spring Bone component

When making adjustments, it's best to change values in play mode to test them, and then transfer the optimal values.

By slightly enlarging the thigh root collider, the skirt no longer clips through!

Adjusting Jiggle Parameters

Based on the original avatar's jiggle behavior, I set the parameters for the jiggle elements as follows. The movements are slightly more rigid than the original to ensure the colliders function properly. The chest has a slightly soft jiggle to maintain a gentle effect. Parameters not listed use the default values when the component is added.

  • Hair

    • Stiffness Force: 2

    • Gravity Power: 0.04

    • Drag Force: 0.6

  • Skirt

    • Stiffness Force: 2

    • Gravity Power: 0.03

    • Drag Force: 0.6

    • Hit Radius: 0.02

  • Chest

    • Stiffness Force: 1

    • Gravity Power: 0

    • Drag Force: 0.14

Additional Note: Using Tools for Setup

For those who find it difficult to set up Spring Bones and colliders individually, there are tools available that can perform these conversions in bulk.

I will report more details after using the tool myself!

Changing Shaders and Adjusting Colors

With this, we've completed about half of the work. Let's keep going for the remaining half!
Next, we'll change the shaders. VRChat avatars often use the lilToon or poiyomi shader, but unfortunately, it is not supported in the VRM format.

Therefore, we need to change it to the MToon shader, which is compatible with VRM. Since the color rendering is different, we need to adjust the parameters to match the original as closely as possible.

First, change the shaders from the material components specified for objects other than the avatar's Armature.

In the Inspector, change the shader to VRM > MToon in the material component.

After making the changes, you'll notice that the colors are different from when using lilToon. The overall appearance is whiter and more pinkish.
This is due to the default settings of MToon, where the shadow color is light pink.
We will need to adjust these.

Match the colors using the left-side reference!

For the Lucifer model, I made the following adjustments:

  • Skin Shade Color: FFFFFF

  • Clothes Shade Color: DAE9FF

  • Hair Shade Color: 8FA2BE

  • Jacket Rim Color: R3:G6:B10

  • Clothes and Tights Rim Color: R0:G3:B14

As a result, it looks like this (the one on the far right shows the adjusted MToon shader colors).

While I got closer, it seems that the shadow color on the clothes tends to get washed out.

Setting Up Expressions

Yes, just a little more to go. Let's keep it up!
The avatar has been converted to VRM, but the expressions are not yet configured. Currently, pressing the emotes provided by cluster will result in a motionless expression.

So, let's set up the expressions.
In the VRM-converted avatar assets, there's a folder named "(Avatar Name).BlendShapes."

This is found in the Assets, not the Hierarchy.

By selecting "BlendShape" in that folder, you can configure the settings in the Inspector.

Cluster supports the following expressions:

  • Neutral

  • Joy

  • Angry

  • Sorrow

  • Fun

  • Surprised

The "Surprised" expression is missing from the initial settings, so we need to add it manually. Click "Create BlendShapeClip" at the top of the screen to create a new expression.

Save it as "Surprised.asset."

Then, assign expressions to all the displayed expressions in this screen. In addition to the above, there are also the following (details :Japaniese):

  • A, I, U, E, O: Correspond to the lip-syncing sounds of "a, i, u, e, o."

  • Blink: Blinking action.

  • Blink_L, Blink_R: Action of blinking one eye.

  • LookUp, LookDown, LookLeft, LookRight: Used for models with eye movement controlled by morphs.

Setting Up BlendShapes

Let's go through this step by step.
First, we'll set up A, I, U, E, O. This involves configuring the shape of the mouth.

In the Inspector, under the "BlendShape" tab, click the triangle next to "Body" to expand it. Look for the blendshape names related to the mouth, likely corresponding to the "A" sound. (The names may vary depending on the model.)

It appears to be mouth.a.

Move the slider of the relevant item all the way to the right (100%). There's a hidden preview section below, so drag the window divider up to enlarge it and verify the expression. Repeat this process for I, U, E, and O.

Next, let's set up Blink. Blink only involves the shape of the eyes.
In the "BlendShape" tab, click the triangle next to "Body" to expand it and find the blendshape names related to Blink. (The names may vary depending on the model.)

This seems to be it. You can see there are options for both eyes and each eye individually.

Just like before, move the slider of the relevant item to 100%. Do the same for Blink_L and Blink_R.

Next, we'll set up LookUp, LookDown, LookLeft, and LookRight, using the same method as before.

These are the relevant section.

Now, onto the expressions. Expressions are composed of multiple parts: eyes, mouth, eyebrows, and others. Some blendshape names clearly indicate their function, like eye_joy and mouth_joy, while others may not match the expression names exactly.

You can double-click the parameter file set in the Expression section of the avatar Prefab's Inspector to expand it, and then click each expression icon under the Facial category to confirm its function.
However, feel free to be creative and register any expressions you like!

Here's the entry point.
Expressions are setting like this. Clicking on the Icon lets you see the expression.

Example Expression Parameters

I set up the expressions based on the original model as follows.

Joy

・Joy
　- eye.smile … 100
　- mouth.smile4 … 100
　- brow.b_tare … 35

Sorrow

・Sorrow
　- eye.open … 100
　- eye.highlight_big … 100
　- eye.cry … 100
　- mouth.triangle … 100
　- brow.b_sad … 100
　- other.tears1 … 100

Fun

・Fun
　- eye.smile_right … 100
　- eye.open_left … 100
　- eye.shiitake … 100
　- mouth.smile3 … 100
　- mouth.upperteeth_up … 100
　- brow.fun … 100

Angry

・Angry
　- eye.angry … 100
　- eye.highlight_x1 … 100
　- eye.eye_small … 25
　- mouth.anger1 … 60
　- brow.b_anger … 100

Surprised

・Surprised (← Be sure to register the Blend Shape Name exactly as this spelling!)
　- eye.eyelashes_up … 100
　- eye.lowereyelashes_down … 100
　- eye.open … 100
　- eye.eyes_small … 40
　- mouth.surprise … 100
　- brow.trouble … 100
　- brow.b_tare … 100

For more details, please refer to this(Japanese) as well.

Optimizing Avatar File Size

VRChat avatars are designed with high-resolution textures for potential modifications. When I exported the current VRM data, it was 124MB.

Large data sizes can cause upload failures to cluster, so we need to reduce the file size as much as possible. Additionally, cluster automatically applies low-quality adjustments if the file size exceeds a certain limit.

Keep this in mind while adjusting.
Open the model's textures from the Assets.

The default settings are as follows.

Currently, there are seven textures. We will resize all of them to 512x512 pixels and apply compression.

Select all the textures, change their settings as shown above, and click the "Apply" button.

This reduces the size to 58MB. It's still not lightweight, so further optimization may be necessary, but that will be covered in another article.

Exporting and Testing the Avatar

Once you've completed the steps so far, upload the avatar to cluster, run it, and check the behavior of the jiggle physics, colors, and expressions to ensure everything is correctly set.

Export the VRM data using "Export to VRM 0.x."
Upload it to cluster.

When you actually use it, you'll notice various things. Adjusting the jiggle physics and colliders requires patience and repeated tweaking.

I noticed that sometimes the bare skin under the tights sticks out when running.

In the future, I plan to write another article on "Optimizing Avatar File Size" that will also cover fixing the issues mentioned above.

That's it for tips on converting a VRChat avatar to VRM and making it usable in cluster! Thank you for sticking with me through this long explanation.

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