Table of Contents
- Troubleshooting
- Quick Troubleshooting
- Installation Issues
- Extension Doesn't Appear After Installation
- Installation Gives Errors
- Cats Tab Not Visible in Sidebar
- Import/Export Issues
- Model Display Issues
- Feature-Specific Issues
- Material Combiner Issues
- Performance Issues
- Error Messages
- "No Armature Selected"
- "No Mesh Found"
- "Shape Keys Not Found"
- "Bone Not Found"
- Policy Violation Warnings (Blender 5.0)
- Getting Additional Help
- Common Workflow Issues
Troubleshooting
Common issues and solutions for Cats Blender Plugin.
Quick Troubleshooting
💡 First Steps: Before diving into specific issues:
- Make sure you're using Blender 5.0 or above
- Verify you have the latest version of Cats
- Restart Blender after installing/updating Cats
- Check that Cats is enabled in Extensions preferences
Installation Issues
Extension Doesn't Appear After Installation
Symptoms:
- Installed Cats but can't find it
- No Cats tab in sidebar
- Extension not in list
Solutions:
-
Check if Enabled:
- Edit > Preferences > Extensions
- Search for "Cats"
- Ensure checkbox is checked
-
Restart Blender:
- Close Blender completely
- Reopen Blender
- Check again
-
Verify Installation:
- Make sure you installed the ZIP file (don't extract it)
- Verify you used "Install from Disk"
- Check you downloaded the Blender 5.0 version
-
Check Blender Version:
- Help > About Blender
- Must be 5.0 or above
- Download correct Cats version for your Blender
5: Ensure the sidebar is open by pressing N
Installation Gives Errors
Possible Causes:
- Wrong Cats version for your Blender
- Corrupted download
- Permission issues
- Conflicting extensions
Solutions:
-
Verify Version Match:
- Blender 5.0 needs Cats 5.0.x.x
- Use version selector
-
Re-download:
- Delete partial download
- Download fresh copy
- Verify file isn't corrupted
-
Check Permissions:
- Ensure Blender can write to extensions folder
- Run Blender as administrator (Windows)
- Check folder permissions
-
Remove Conflicting Extensions:
- Old Cats versions
- Incompatible add-ons (Like MMD Tools, cats comes with the latest MMD Tools, there will conflict with each other)
- Restart after removal
Cats Tab Not Visible in Sidebar
Solutions:
-
Press N:
- In 3D Viewport, press N key
- Toggles sidebar visibility
-
Look for Cats Tab:
- Check all tabs in sidebar
- Should see "Cats" tab
- Click to open
-
Verify Extension is Enabled:
- Edit > Preferences > Extensions
- Find Cats
- Check enabled checkbox
Import/Export Issues
Model Won't Import
Symptoms:
- Import button does nothing
- Error messages during import
- Blender crashes
Solutions:
-
Check File Format:
- Verify supported format (.pmx, .pmd, .fbx, .vrm, etc.)
- File isn't corrupted
- File size is reasonable
-
Check File Path:
- No special characters in path
- Path isn't too long
- File isn't in use by another program
-
Try Blender's Native Importer:
- File > Import
- If that fails, file may be corrupted
-
Check Console for Errors:
- Window > Toggle System Console
- Look for error messages
- Report specific errors
Model Display Issues
Model Appears Black or No Textures
Symptoms:
- Model is all black
- Textures don't show
- Materials look wrong
Solutions:
-
Switch Viewport Shading:
- Press Z key
- Select "Material Preview" or "Rendered"
- "Solid" mode may not show textures
-
Check Material Properties:
- Select mesh
- Open Material Properties panel
- Verify materials exist
- Check if textures are loaded
-
Texture Paths:
- Materials may reference missing textures
- Relink textures if needed
- Use "Find Missing Files" in Blender
-
After Material Combiner:
- This is sometimes expected in Blender
- Set up materials properly in Unity
- Check Material Combiner troubleshooting
Model is Inverted/Inside Out
Symptoms:
- Mesh appears inside-out
- Backfaces showing
- Shading looks wrong
Solutions:
-
Recalculate Normals:
- Other Options panel
- Click "Recalculate Normals"
-
Check in Edit Mode:
- Tab to Edit Mode
- Enable Face Orientation (overlay)
- Blue = correct, Red = inverted
-
Flip Normals if Necessary:
- Select all faces
- Use "Flip Normals" in Other Options
- Only if entire mesh is inverted
Wrong Scale in VRChat/Unity
Symptoms:
- Avatar too big or too small
- Not at expected height
- Proportions wrong
Solutions:
-
Check Scale in Blender:
- Use Scaling panel
- Measure actual height
- Scale to correct size (160-180cm recommended)
-
Apply Transformations:
- Other Options
- "Apply Transformations"
- Before export
-
Unity Import Scale:
- Should be 1.0 for FBX
- Check import settings in Unity
- Don't scale in Unity, scale in Blender
Feature-Specific Issues
Eye Tracking Not Working
Symptoms:
- Eyes don't move
- Blinking doesn't work
- Setup seems broken
Solutions:
-
Verify Bone Selection:
- Eye Tracking panel
- Check head, left eye, right eye bones selected
- Use correct bones
-
Check Weight Painting:
- Eyes must be weighted to eye bones
- 100% weight recommended
- No weight bleeding
-
Test in Blender:
- Use test controls in Eye Tracking panel
- Verify eyes move
- Check blinking shape keys
-
Material Combiner Order:
- Did you run Material Combiner after eye tracking?
- Set up eye tracking after material combining
- May need to redo setup
Visemes Don't Work
Symptoms:
- Mouth doesn't move for lip sync
- Shape keys not assigned
- Preview doesn't show movement
Solutions:
-
Check Shape Key Assignment:
- Visemes panel
- Verify Mouth A, O, CH assigned
- Use correct shape keys
-
Verify Shape Keys Exist:
- Select mesh
- Open Shape Keys panel
- Confirm mouth shape keys present
-
Test with Preview:
- Use preview in Visemes panel
- Check each viseme individually
- Adjust intensity if needed
-
Translation Issues:
- Translate shape keys before viseme setup
- Don't translate after setup
- May break references
Bone Merging Causes Issues
Symptoms:
- Model breaks after bone merging
- Weights look wrong
- Animations broken
Solutions:
-
Check Merge Settings:
- Optimization panel
- Start with lower merge ratio (0.5)
- Enable "Keep Merged Bones" for safety
-
Test Before Cleanup:
- Merge bones first
- Test thoroughly
- Clean up only if merge is good
-
Verify Armature After:
- Check bone hierarchy
- Test animations
- Verify weights look correct
-
Undo if Necessary:
- Ctrl+Z to undo
- Try different settings
- Or work from backup
Material Combiner Issues
Materials Turn Black/White
Symptoms:
- After Material Combiner, materials are black or white
- Textures missing
Possible Causes:
- Materials don't have assigned textures
- Shader incompatibility
- VRM addon version issues
Solutions:
-
Check Textures:
- Verify materials have textures assigned
- Relink missing textures
-
Note:
- Material Combiner is a 3rd party plugin
- Not part of Cats
- Our fork is for Blender 5.0+ only. For Blender 4.x or older, use the original Material Combiner repo
- Check the appropriate Material Combiner repo for help
Atlas Missing Textures
Symptoms:
- Not all textures appear in atlas
- Materials merged but atlas incomplete
Possible Causes:
- Textures are packed in .blend file
- Non-English Blender version
- Unsupported shader
- Materials already share textures
Solutions:
-
Unpack Textures:
- File > External Data > Unpack Resources
- Unpack All Into Files
- Save to location of your choice
-
Check Blender Language:
- Must be set to English
- Node names are language-specific
- Switch to English and regenerate nodes
-
Verify Shader Support:
- Check Material Combiner documentation
- Some shaders aren't supported
- May need to change shader type
-
Already Optimized:
- If materials already share texture, won't be re-atlased
- This is normal behavior
Pillow Installation Keeps Repeating
Symptoms:
- Pillow installation prompt every time
- Installation fails
- Can't use Material Combiner
Possible Causes:
- VPN interference
- Windows Store Blender
- Permission issues
Solutions:
-
Disable VPN:
- Turn off VPN temporarily
- Try installation again
-
Manual Installation (Windows):
1. Navigate to Blender folder\5.0\python\bin 2. Copy this path 3. Press Win+R, type cmd.exe 4. In console: set PythonPath="Your\Copied\Path" %PythonPath%\python.exe -m pip install Pillow --user --upgrade -
Manual Installation (macOS):
/Applications/Blender.app/Contents/MacOS/Blender -b --python-expr "__import__('ensurepip')._bootstrap()" /Applications/Blender.app/Contents/MacOS/Blender -b --python-expr "__import__('pip._internal')._internal.main(['install', '-U', 'pip', 'setuptools', 'wheel'])" /Applications/Blender.app/Contents/MacOS/Blender -b --python-expr "__import__('pip._internal')._internal.main(['install', 'Pillow'])" -
Avoid Windows Store, Snap, Flatpack and package managers Blender:
- Download from blender.org instead or ust the steam version.
- Windows Store version has permission issues and Linux Package manager build there own version with a different python version. This can cause issues.
Performance Issues
Cats Operations Very Slow
Symptoms:
- Tools take minutes to complete
- Hang or freeze during operations
Possible Causes:
- Very complex model
- Many objects/meshes
- Slow computer
Solutions:
-
Be Patient:
- Complex operations take time
- Cats is working
- Check console for progress
-
Simplify First:
- Remove unnecessary objects
- Join meshes before operations
- Clean up model first
-
Close Other Programs:
- Free up RAM
- Close browser, etc.
- Give Blender resources
Error Messages
"No Armature Selected"
Solution:
- Select your armature object
- Must select armature, not mesh
- In Object Mode
"No Mesh Found"
Solution:
- Ensure meshes are present
- Meshes must be parented to armature
- Check object visibility
"Shape Keys Not Found"
Solution:
- Verify mesh has shape keys
- Check correct mesh is selected
- Shape keys must exist for viseme/eye tracking
"Bone Not Found"
Solution:
- Verify bone names
- Refresh bone list
- Check bone exists in armature
Policy Violation Warnings (Blender 5.0)
Symptoms:
- Warnings about extension policies
- Alerts about legacy methods
This is Expected:
- Cats uses legacy methods for third-party addons
- Warnings are safe to ignore
- Everything still works correctly
- No action needed
Getting Additional Help
Before Asking for Help
- Check This Page: Many issues covered here
- Read Relevant Wiki Pages: Feature-specific guides
- Try Search: Discord/GitHub for similar issues
- Verify Version: Using supported Blender 5.0+
When Asking for Help
Include:
- Blender version (exact)
- Cats version
- What you're trying to do
- What happens instead
- Error messages (exact text)
- Screenshots if relevant
- Console output if available
Where to Get Help
- Discord: Community chat and support
- GitHub Issues: Bug reports and feature requests
- This Wiki: Documentation and guides
What NOT to Report
- Issues with unsupported Blender versions or blender versions which are not the blender.org or steam version (anything before 5.0 is not supported)
- Third-party extension problems (Material Combiner, etc.)
- General Blender questions (use Blender forums)
- Feature requests without discussion first
Common Workflow Issues
Order of Operations Wrong
Many issues stem from wrong order:
Correct Order:
- Import model
- Fix MMD (if MMD model, fresh only)
- Translate names
- Apply transformations if needed
- Combine materials/Create atlas
- Set up eye tracking
- Set up visemes
- Final optimization
- Export
Key Point: Material Combiner BEFORE eye tracking and visemes!
Backup Management
Always Keep Backups:
- Before major operations
- After completing stages
- Save incremental versions
- Use version control if possible
Good Backup Practice:
my_model_01_import.blend
my_model_02_fixed.blend
my_model_03_optimized.blend
my_model_04_rigged.blend
my_model_05_final.blend
Related Pages:
- FAQ - Frequently asked questions
- Installation - Setup help
- Version Support - Compatibility info
- All feature pages for specific tools
Please do not report any issues for Blender version below 5.0