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MMD Options

The MMD Options panel provides tools specifically designed for preparing MMD (MikuMikuDance) and VRM models for VRChat.

⚠️ WARNING: FIX MMD MODEL SHOULD ONLY BE USED FOR FRESH MMD/VRM MODELS THAT HAVE NOT BEEN SET UP FOR UNITY.

DO NOT USE THIS IF:

• Your model was purchased from Gumroad, Booth, or similar stores
• Your model has already been set up for Unity
• You are creating your own custom model from scratch
• The model has already been processed for VRChat
• This also applies for Offical Cats, Fix Model was never a Fix everyone solution but a converter for certain formats.

When to Use MMD Options

Use these tools ONLY when you have:

• A fresh .pmx or .pmd file from MMD
• A .vrm file directly exported from VRoid or another VRM creator
• Cerain other model types maybe supported

Features

Fix MMD Model

This is the main tool for converting MMD/ VRM models to be Unity/VRChat-ready.

What It Does:

1. Reparents Bones

   • Reorganizes bone hierarchy for Unity
   • Fixes parent-child relationships
   • Establishes proper bone structure

2. Removes Unnecessary Bones

   • Deletes bones not needed for VRChat
   • Removes MMD-specific bones
   • Cleans up the armature

3. Renames and Translates Objects/Bones

   • Converts Japanese names to English
   • Standardizes bone naming
   • Makes bones VRChat-compatible

4. Mixes Weight Paints

   • Redistributes vertex weights
   • Fixes weight painting issues
   • Ensures smooth deformations

5. Rotates Hips

   • Adjusts hip bone rotation for Unity
   • Fixes T-pose issues
   • Aligns model correctly

6. Removes Constraints

   • Deletes MMD-specific constraints
   • Removes incompatible IK setups
   • Cleans constraint system

7. Deletes Unused Vertex Groups

   • Removes empty weight groups
   • Cleans up vertex data
   • Reduces file size

How to Use:

1. Import your fresh MMD or VRM model using Quick Access importer
2. Select the armature
3. Click Fix MMD Model
4. Wait for the process to complete (may take a minute for complex models)
5. Review the result

Fixed Materials (Deprecated)

📝 Note: This feature has been removed as of version 4.2.

Why it was removed:

• Materials should be set up directly in Unity, not embedded in FBX
• Embedded materials increase file size unnecessarily
• Increases memory usage in both Unity and VRChat
• Not recommended for performance optimization
• Previous material fixes were for older VRChat requirements (no longer necessary)

What to do instead:

• Export your model with textures
• Set up materials in Unity using the VRChat shader
• This gives you more control and better performance

Combine Materials

Merges multiple materials into fewer materials:

• Reduces draw calls
• Improves performance
• Simplifies material management
• Maintains texture assignments

How to use:

1. Select your model
2. Click Combine Materials
3. Materials with similar properties will be merged

💡 Tip: Do this after fixing the MMD model and before creating texture atlases.

Remove Rigid Bodies and Joints

Removes physics components from MMD models:

• Deletes rigid body data
• Removes joint constraints
• Cleans up physics setup
• These aren't used in VRChat

How to use:

1. Select your model
2. Click Remove Rigid Bodies and Joints
3. Physics components will be removed

ℹ️ Note: VRChat uses Unity's physics system, so MMD physics aren't compatible.

Typical MMD to VRChat Workflow

Follow these steps for best results:

1. Import the Model

• Use Cats' Quick Access importer
• Select your .pmx, .pmd, or .vrm file
• Wait for import to complete

2. Fix MMD Model

• Click Fix MMD Model in MMD Options
• This handles all the major conversions
• Be patient - complex models take time

3. Remove Physics (If applicable)

• Click Remove Rigid Bodies and Joints
• Cleans up unused physics data

4. Combine Materials (Optional)

• Click Combine Materials if you have many materials
• Helps with performance

5. Optimize

• Use Optimization tools
• Create texture atlas
• Merge bones if needed
• Remove doubles

6. Set Up Features

• Configure Eye Tracking
• Set up Visemes for lip sync
• Add any custom shape keys

7. Export

• Use Quick Access export
• Export as FBX for Unity
• Import into Unity and set up materials there

Common Issues

Model Looks Broken After Fix MMD Model

Possible causes:

• Model was already Unity-ready (don't use Fix MMD Model on these!)
• Model has custom bone structure
• Import failed partially

Solutions:

• Undo (Ctrl+Z) and don't use Fix MMD Model
• Re-import the original model
• Check if model came from a store (if yes, don't fix it)

Bones Have Weird Names

This is normal! After Fix MMD Model:

• Japanese names are translated
• Bones are renamed to English
• Names are standardized for VRChat

Some Materials Are Black

Possible causes:

• Textures didn't import correctly
• Material needs to be set up in Unity
• Shader incompatibility in Blender

Solutions:

• Check texture paths in material settings
• This is often fine - set up materials properly in Unity
• Use Convert All to PNG in Optimization panel

Model Is Rotated Wrong

This is usually fine:

• Blender and Unity use different coordinate systems
• Export handles rotation automatically
• Model will be correct in Unity

VRM-Specific Notes

VRM models often need the same treatment as MMD models:

• Use Fix MMD Model on fresh VRM files
• VRM files exported from VRoid need fixing
• Already-processed VRM models should not be fixed

VRM Add-on Integration

Cats works alongside the VRM Add-on for Blender:

• Use VRM Add-on to import .vrm files
• Use Cats to process and optimize
• Both can be installed together

Best Practices

DO:

• ✅ Use Fix MMD Model on fresh MMD/VRM imports
• ✅ Remove rigid bodies and joints
• ✅ Combine materials after fixing
• ✅ Optimize after all MMD-specific fixes
• ✅ Set up materials in Unity, not Blender

DON'T:

• ❌ Use Fix MMD Model on store bought models
• ❌ Use Fix MMD Model on already processed models
• ❌ Use Fix MMD Model on custom made models
• ❌ Skip optimization after fixing
• ❌ Embed complex materials in FBX (use Unity for materials)

Understanding the Process

Why Bones Need Fixing

MMD uses a different bone structure than Unity/VRChat:

• Different naming conventions (Japanese vs English)
• Different bone hierarchies
• Different bone rotations
• MMD-specific helper bones

Why Physics Doesn't Transfer

MMD physics uses Bullet physics:

• Unity uses PhysX
• Systems are incompatible
• VRChat doesn't support MMD physics
• Must be rebuilt in Unity if needed

Why Materials Are Handled in Unity

Blender materials don't directly translate to Unity:

• Different shader systems
• VRChat uses specific shaders
• Better control in Unity
• Smaller file sizes

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Related Pages:

• Quick Access - Import/Export tools
• Optimization - Post-processing optimization
• Visemes - Setting up lip sync
• Eye Tracking - Setting up eye movement