Seam Blend — Blend away the neck line where head and body meshes meet [VRChat / Unity / lilToon] (Free trial available)

Common problems it solves

• After tying up the hair or changing to an outfit without a collar, a line shows across the middle or base of the neck.
• The neck line appears or disappears depending on the light direction.
• The head and body are separate meshes and the shading does not match at the joint.
• Fixing normals in Blender is a lot of work, and you want to keep the original avatar.
• You are not sure which meshes are joined to which.

What makes it different

• A Free trial: find the seams on your own avatar and preview the result before buying.
• Seams are found automatically; you do not need to pick the two meshes by hand.
• Before you press anything, the window shows how much the seam mismatch drops (in degrees) and which meshes and materials will change.
• Preview in the Scene and Game views, and switch between before and after.
• The files it makes are new copies in a new folder. "Restore" puts back only what this tool swapped.

About Seam Blend

Tested in VRChat.

Seam Blend is a Unity editor extension that blends away the line across the neck where the head and body meshes meet. It finds where two meshes are joined, makes the shading direction (normals) match at the seam and blends the band around it. When lilToon rim shade differs between head and body, it fades rim shade near the seam. The window can switch between English and Japanese.

No avatar models are included (tool only).

What it does

• Put the avatar into the window and press "Find seams". Seams around the neck are ticked from the start.
• Adjust "Band width" (2.5 cm by default) and "Strength" while watching the preview.
• Full version: "Save and use" makes copies of the changed meshes/materials and mask textures (new files) and swaps only those meshes and material slots. One Ctrl+Z undoes it (the created files stay).

Free vs Full

• Free trial: find seams and preview the result. It cannot save.
• Full: everything above plus "Save and use" (goes into your upload) and "Restore".

Tested

Seams were searched on 11 free avatars. A neck seam was found and ticked on 6 of them (Felis, Yumeka, RadDoll, Julius, Pochi, Lapine), and on all of them the seam mismatch after blending was under 1 degree. A blended and saved avatar was loaded and worn in VRChat, with hair and accessories intact. Bone weights, vertices, UVs, shape keys and the original files stay the same, and both one Ctrl+Z and "Restore" undo it. After the same processing as an upload (Modular Avatar and other build steps), the two sides of the seam still match.

Notes

On avatars whose head and body are one mesh, or that do not share vertices at the neck, no seam is found (Omaneko, Watacomeco, Inuinu). Seams that already match (Hayakawa Aoi, Haolan) and seams not around the neck are left unticked. Shadow settings (shadow strength, shadow color, etc.) are not changed; if they differ between head and body, a faint line may remain when light comes from the side (the window lists the differing settings). Colors are not blended, gaps are not closed and bone weights are not copied, so a color difference after putting another avatar's head on is not fixed. Normals are fixed for the shape with all shape keys at 0; moving a shape key that affects the neck may show a faint line. Rim shade fading works only on opaque lilToon materials (not Lite, Multi, Fur and similar variants). Materials that already have a rim shade mask, materials with scrolling UV settings, materials whose main texture does not repeat while the UVs go outside, and meshes where a single triangle spans more than one full UV tile are not changed either (the window tells you why). While the preview is shown, the NDMF preview in the scene (Modular Avatar etc.) is paused; it comes back when you turn the preview off or close the window. Meshes with Read/Write off and avatars with non-uniform scale cannot be searched (the window tells you why). Prefab Mode and Project prefabs are not supported. The created meshes and materials are copies of the original avatar's; follow the terms of the original avatar and clothes.

Requirements

Unity 2022.3 (tested on 2022.3.22f1). lilToon (tested on 2.3.4); non-lilToon materials get the normals fix only.

How to install

1. Drag SeamBlend*.unitypackage into the Unity Project window and press Import.
2. Menu: Tools > Seam Blend.
3. Put an avatar into the window and press "Find seams".

Importing the Full version over the Free trial replaces it.

Terms

Personal and commercial use are both OK. You may upload, stream and take photos with avatars that use meshes, materials and textures made with this tool. Follow the terms of the original avatar and clothes. Do not redistribute or resell the tool itself. Use at your own risk.

Questions or bug reports: please send a message through the shop.

Developed with AI assistance (coding and testing). The store cover frame was made with generative AI.