Update: v1.0/2.0 trial is no longer available.

Universal Belly Bump and Mesh Deformation Tool for Unity

Walkthru video available on my twitter and youtube.

Shape* ANY avatar without leaving Unity! AND I MEAN ANY

The back and forth between Blender and Unity is no fun (especially if you don't know blender). If you want to add a belly bump or other mesh deformation and have it triggered by other vrchat avatar systems without the hassle, this is the tool for you. Auto Belly Bulge v3 provides an easy-to-use, non-destructive mesh deformation workflow for modifying avatars in unity.

* in a somewhat specific way lol

The uses are endless †

Make it look like your avi just had a big meal. A whole deer maybe?! (Don't do that, they're too cute). Stung by a bee? A third thing perhaps?

† unfortunately SPS socket technology bottoms out at 3

DID I SAY UPDATE!

If the initial release was just a pig (a handsome pig) but a pig nonetheless, and Version 2.0 was some slapdash lipstick on that pig... v3 is a fully tarted up hog 🐷💅

UX CHANGES

• Separate Standard Mode and Engineer mode
• Standard is a straight-to-the-point 😉 no-frills workflow that gets you from boring avatar base to bulging menace in 4 steps.
• Engineer is for people who want to tweak literally everything. If you've been more than 6 menus deep in your bios after clicking "I accept the risk" you'll enjoy it here.
• Different steps of the process are clearly delineated
• A backup system built around rolling back and tracking multiple versions

UI CHANGES

• I'm all about tabs now babyyy
• I stole the design language from poiyomi (and THEN THEY CHANGED IT... but their new version is better, so I will be stealing that as well lol)
• Ability to toggle off verbose help text in Engineer Mode
• The main theme of this update was fixing the user experience for folks who only need the basic bulge (with lovely default settings selected by myself I might add)
• A (still improving) interface for the backup system
• Targeting gizmo control is more natural and intuitive
• LOTS OF HELP TEXT...MAYBE TOO MUCH

SPS UPDATES

• (Re)Creates existing SPS SFX on new socket (requeries Wholesome 2)
• Automatically snap entrance of drawn bulge path to existing socket
• SPS2 made everything better

MESH TARGETING

• It's visual now!!!!!!!!!!!!!!!11!1one!
• The primary method of selecting where to deform your avatar is a pen tool with which you trace out where you'd like the bulge to appear on your avatar, in unity. (See the third image).
  

EVERYTHING HAS AS TOOLTIP. I mean it. And it comes with a comprehensive guide just a tab away. It's a bit much honestly, but it is there. Also there is the ability to disable SOME of the guidance cluttering up the UI.

Key Features

• *Non-destructive workflow*: works on mesh clone and saves separate asset.
• *Intuitive shaping tools*: move/rotate each stop of the deformation path by hand or let AB3 provide sane defaults with which you can fool around
• *Vertical profile control*: vertical gradient slider allows you to choose where the weight sits on the body. Create anything from a low "fupa" look to a "top-heavy" full belly.
• *Directional bias*: pushes forward instead of outwards avoiding the "balloon" look relative to the hips.
• *Predictive Visualization*: get a live preview off what the results will be before baking. Intuitive controls + preview make things easy. All changes are shown in real time.
• *Integrated smoothing*: relaxing the mesh edges reduces spikes or sharp ridges at top or bottom of the deformation.
• *CTRL+Z and Undo History*: not what you expected? Undo to the rescue!
• Automatic SPS Setup: start from scratch or base your bulge on an existing socket and port existing SFX controllers
• 1-step or 3-step blendshapes: AB3 bakes 3 separate blendshapes for the deformation path along with a single blendshape comprising of all 3.

Technical stuff

• Save Location: Assets > AB3
• The edit mode live preview is naturally at little resource hungry.
• Compatibility: any Skinned Mesh Renderer (body, face, etc.)
• That includes attached clothing with a BETA clothing layer deformation offset
• New Versions INCOMPATIBLE with old versions, meaning, if you want to upgrade for new features you will need to go back to an unaltered version of your model (so just your original fbx/asset)
• The backup feature is for your peace of mind (and for advanced users to test with other mesh-modifying tools). The process is non-destructive to your original model.

IMPORTANT NOTES

AI Policy: I code in a modern development environment/cloud infrastructure and use automated systems for debugging, testing, and security checks (primarily within github). Guide and tooltip text grammar/spelling checks provided by grammarly and Word. Unit testing is mostly automated.

Trial Version: You can preview the deformation if you want to guarantee it functions as you expect (or if you have a crazy modified avatar there could be issues). PREVIEW IS OF VERSION 1 FOR THE MOMENT SORRY

Activation: the first unity project you import this into will have you enter the jinxxy serial provided on the download page. 3 active seats with a button to move the seat with a click.

If this seems over-engineered, that is correct. And if you read this far hiiiiii you're the first to know that the the bulge mechanic has/is being ported to veins, toe beans, and MORE! Coming soon to a theatre near you 😉 I'm thinking of a new name for the whole suite tho... Bulge-O-Matic 3000? When it comes out i'll put a super discount code [HERE] for a bit *shh*

How to Use

1. Tool menu under Tools > TimmyTimYAY
2. Select Avatar
3. Draw bulge path
4. Adjust until satisfied in preview mode
5. Bake
6. SPS Attach
7. Enjoy

Hit me up on Discord: timmytimyay if u have issues -- i am anxiety so pls be patient lol

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Version 2.0 Information:

Known Good (tested)

• Viwi
• Nardodragon
• Mayu
• Winterpaw Canine
• Winterpaw Feline
• Spiravali
• LiliumPanthera
• Deuzear
• Meowper
• Kita'vali LWD MOD ONLY*
• Malibu from Sturmwolf

Reported Good (user report, send me your!)

• Fennix
• SabreanV2

Fixes/Mitigations/Patches

• Novabeast and edits (avatar is weird, misaligned and with inverted axis, use the "Invert_mod" version of the tool - sorry no trial version yet as it needs more testing) Seems to be consistently misaligned along Y-axis. See novabeast screenshot for reference (note the gizmo is also has a negative rotation).
• Specific settings for the novabeast are now included on the downloads page.
• Specific settings for the Kita Lwd Mod are now included on the downloads page.*

Known Potential Issues (Please get trial first)*********

• Khnfu Cat (incorrect offsets)
• Kita'vali NORMAL (both original 4.8 version as well as the '2025 Modern' version).
• Mallkin-2000 Avatar Studio Builderis not supported at this time (updated 8/27/26)
• Mayu Adult patch by solocat does not work due to the many patched-in folds
• I imagine ANY use of shell texturing for faux-fur will make it look pretty funky lol

It's possible to move the deformation gizmo around to hunt for the mesh points and eyeball it but this is not consistent behavior.

If the mesh is misaligned, it is likely to be very spikey with default settings, get extreme with your bias dial and smoothing amount.

Avatars with possible issues I don't own so can't test:

• Deira Base
• Sabreans
• Bennett

I only have experience with furry avatars, so e-boys/girls/enbys are in uncharted waters.

Previous Versions

2.0

• Automatic SPS setup and integration with visual guide
• Split into Single-Blendshape (Classic) and Multi-Stage-Modes
• Configurable axis-offset mitigations
• Simple GUI for customizing bulge logic
• A VERY USEFUL STEP BY STEP GUIDE TAB IN-UNITY
• Advanced mode customizations including per-blendshape-weight and depth-triggered blendshape overlap)
• Sane defaults for most avatars
• License updated to relax terms allowing for use in commissions

Version 1.3.22 (InvertMod):

• Fixed issue with steps not being added to undo buffer
• Axis-invert options presented for broken models

TOS

1. Personal & Commercial License

• Personal Use: You may use this tool to modify your own personal avatars for platforms such as VRChat, ChilloutVR, or Resonite.
• Public Avatar Uploads: You are permitted to upload avatars using generated meshes as "Public" on social VR platforms, provided the upload complies with that platform's specific Terms of Service.
• No Mesh Distribution: You may not distribute, sell, or share the generated meshes as standalone files or as part of an avatar package (Unity Package, Prefab, etc.) to any third party, except as explicitly permitted under the Limited Commercial Use section below.
• Limited Commercial Use (Commissions): You may use this tool for one-off, single-avatar commissions for individual clients, provided you meet the following two requirements:
  - Both Parties Must Own a Copy: Both the artist (commissioner) and the client must legitimately own a copy of the BellyBulge tool
  - Mandatory In-Game Credit: You must include visible credit on the avatar's expression menu. This must be placed specifically under the SPS menu as a non-functional item reading BellyBulge by\ntimmytimyay, or by utilizing the provided menu icon for the SPS toggle.

2. Restrictions

• No Redistribution: You may not resell, share, or redistribute the source code, script, or editor window of this Software, in whole or in part, to any third party.
• Full vs. Trial Version: * The Full Version is licensed to a single user.
• The Trial Version is provided for evaluation purposes only. You agree not to attempt to circumvent, defeat, or modify the trial limitations
• No Obfuscation Removal: You may not decompile or reverse-engineer the software for the purpose of removing licensing checks or trial restrictions.

3. Ownership & Copyright

• TimmyTimYAY retains all ownership and copyright of the Software source code.
• The user retains ownership of any BlendShapes or Meshes generated by the tool, provided they have the legal right to modify the original base mesh.

4. Liability & Warranty

• "As-Is" Basis: The Software is provided "as-is" without warranty of any kind.
• Mesh Backups: While the tool is designed to be non-destructive, the Software is not responsible for any data loss, mesh corruption, or scene breakage. Always back up your project before performing mesh deformations.
• Third-Party Compatibility: Compatibility with future Unity versions or VRChat SDK updates is not guaranteed, though efforts will be made to maintain the tool.

5. Refund Policy

• Due to the digital nature of this product, all sales are final. No refunds will be issued once the product has been downloaded. Please use the Trial Version to ensure compatibility with your workflow before purchasing.