Spine-IO Open source Spine 4.3 JSON Exporter for Blender — OCA/OCO-friendly pipeline

Author: Simon Heggie Status: Experimental (Alpha) Blender: 4.2+ Spine Target: 4.3.39-beta License: GPL-3.0 license

CLICK THE VIDEO THUMBNAIL BELOW TO SEE A DEMONSTRATION:

What is Spine-IO?

Spine-IO is a set of tightly-integrated Blender extension modules that export Blender armatures, meshes, weights, UVs, and blend-modes into valid Spine 4.3 JSON — supporting complex deformation meshes, OCA/OCO workflows, and non-destructive material setups.

For now this is just an exporter, but I called this IO because Importing is planned.

Installation (Easy)

Go to your Extensions manager in Preferences, search for 'Spine-IO' and download.

Installation (Manual)

As a Blender 4.2+ Extension (recommended)

Go to Edit → Preferences → Extensions.

Install from ZIP (or symlink into the extensions directory).

Enable “Spine-IO (Spine 4.3 JSON Exporter)”.

As a legacy Add-on

Edit → Preferences → Add-ons → Install…

Choose the ZIP file.

Enable Spine-IO (Spine 4.3 JSON Exporter).

Where it appears in Blender

File → Export → Spine (.json) — opens export dialog

3D Viewport → Sidebar → Spine-IO tab — Quick Export + Blend-Mode Manager containing:

• Quick Exporter (including Texture export ON/OFF)

• Blender mode manager.

CURRENT WORKING FEATURES

✔ Full Mesh Pipeline

Tris, quads, ngons → correctly triangulated

Internal edges supported

Spine-compatible edge encoding

Automatic hull detection

Works for weighted and unweighted meshes*

✔ Bones & Armature

All bones exported with correct parent hierarchy

Bone lengths correctly computed

Accurate transforms using local rig-space frame

Auto-scaled export (or constant scale mode)

✔ Weights

Up to 4 influences per vertex (configurable)

Automatic fallback bones

Correct per-bone coordinates in Spine space

✔ Animations

FK only (for now)

Exports one Blender Action bound to the armature

Spine-compatible timelines

✔ Materials → Spine Blend Modes

A full procedural BLEND-MODE node is generated automatically for materials with the BLEND-MODE node applied. On the right side menu in the viewport in 'Spine-IO' under 'Spine Blend-Modes', you can add this effect to your materials from a blend mode drop down from a list of your selected objects.

Normal

Add (screen)

Luminosity (Spine “additive”)

Multiply

The exporter detects the active material blend output and writes:

"blend": "normal|additive|multiply|screen"

✔ UI Tools

Quick Export (no dialog, uses remembered path)

Safe file-path resolver

Real-time blend-mode syncing via background timer

Material browser inside the Spine-IO panel

✔ OCA/OCO-compatible Image Pathing

Automatically strips .OCA/ folder

Normalizes child texture directories

Subfolders preserved automatically

Works even with mixed or unusual folder structures

Blender → Spine image mapping is stable and predictable

✔ Automatic Parenting Fix

Weighted meshes get properly attached to the correct armature bones even if the mesh was left unparented in Blender.

KNOWN ISSUES / BUGS

⚠ ### 1. Occasional UI Slowdown

The background sync timer (_sync_material_blend_modes) can cause:

momentary pauses in the UI

rare dependency graph updates

Cause: Scanning all materials every 0.5 seconds Status: Needs throttling, caching, or a smarter event-based trigger.

⚠ ### 2. Root bone world-space rotation hack

Currently the exporter still relies on the 90° rotation patch in rig-space conversion.

Status: Export still works, but we want a clean rig-space transform. You require to manually use a root bone as the first and top most bone in the hiearchy that stays in the centre of the world, and you must keep it locked and zeroed.

In the future I will automate this for the user and adjust the world coordinate conversation process so that he 90 degree is no longer required.

⚠ ### 3. Only FK animation supported

This is a limitation, not a bug — but worth noting. The next thing to be supported for this is IK controls.

⚠ ### 4. Only weighted meshes are supported at the moment. *

If you attatch a non-weighted mesh it will be in the centre of the world.

ROADMAP — NEXT FEATURES TO ADD

🔥 High Priority (Character Animation Requirements)

Correct world → Spine transform (remove 90° hack)

Add support for controller bones (non-deforming bones)

Driver support

especially bone-driven alpha

later: shader-based effects or colour drivers

IK and Constraints

🔥 Medium Priority

Multiple Action export → multiple Spine animations

Skin swapping (Spine skins)

Slot colour and dark-color export

Two-colour tint support

Automatic PSD/Krita layer naming → slot names

🔥 Low Priority (but eventually needed)

Full Importer for Spine → Blender

UI merging for multi-rig scenes

Export presets (profiles for Godot/Armory/Unity)