Reference

Compatibility

Rhea runs on Blender 4.0 through 5.x, on every operating system Blender supports, with no dependencies to install. Here is what that means in practice and where the edges are.

Supported versions

Blender 4.0 – 4.1legacy zip: Install rhea-legacy-1.0.0.zip through Preferences → Add-ons. These versions predate Blender's extension system entirely, which is why a second file exists.
Blender 4.2 – 5.xextension zip: Install rhea-1.0.0.zip through Preferences → Get Extensions → Install from Disk. This is the file almost everyone wants.

Both are built from one source tree and contain the same features. The only difference is packaging metadata. See Installation.

Feature parity across versions

Every module, every operator, every preset works identically on every supported version. There is no reduced feature set on older Blender.

Achieving that took some work, because several relevant APIs changed across the range — custom split normals were replaced in 4.1, Geometry Node identifiers and socket interfaces drifted repeatedly, and NumPy's type promotion rules changed between the version shipped in 4.0 and the one shipped in 5.x. All of that is absorbed in a single compatibility module rather than being scattered through the codebase, and the full test suite runs against 4.0, 4.2, 4.5 LTS and current 5.x.

If you are choosing a version

Blender 4.5 LTS is the safest choice for production work — long-term support, and the version most third-party add-ons target. Rhea behaves identically on it and on 5.x.

Operating systems

Windows: 10, 11
macOS: Intel and Apple silicon
Linux: Any distribution Blender supports
Platform-specific builds: None

The same two files serve every platform. Rhea contains no compiled code, no wheels and no binaries, so there is nothing that can be built for the wrong architecture.

Dependencies

None beyond what Blender already ships. Specifically: numpy, mathutils, bmesh, bpy and gpu, all bundled with Blender.

There is no pip step, no Numba, no scipy. Anything scipy would have provided — KD-trees, sparse solves — is implemented against Blender's own mathutils.kdtree or hand-written in numpy. This is deliberate: an optional accelerator that has to be downloaded is an accelerator that fails behind corporate proxies, restricted user accounts and offline machines, and then the tool is slow for exactly the people who cannot fix it.

Python versions

Blender 4.0 ships Python 3.10, 4.1 through 4.5 ship 3.11, and 5.x ships 3.13. Rhea's code targets 3.10 syntax throughout so it runs on all three without conditional parsing.

File compatibility

Scenes are portable. A .blend saved with Rhea opens on any supported version.
Live results need Rhea installed. The controls live in a Geometry Nodes modifier plus add-on properties. Open the file without Rhea and the geometry still evaluates, but the panel controls are gone.
Applied results need nothing. Plain mesh data. Anyone can open it, with or without Rhea, forever.
Presets are JSON and portable between machines and versions.

Sending a file to someone without Rhea

Apply the stack on a duplicate and send that. It is plain geometry with no requirements attached.

Working with other tools

Native modifiers: Rhea's modifiers sit in the normal stack and interoperate normally. Fields written to vertex groups can drive any native modifier that accepts one.
Geometry Nodes: Rhea authors standard node groups prefixed RHEA_. You can open them, inspect them and modify them — though a rebuild will replace your changes, so copy the group first if you intend to keep them.
Sculpting and retopology: Apply first. Sculpt tools need real geometry to grab.
Export formats: Apply first, or use a format that evaluates modifiers on export. FBX, glTF, OBJ, USD and Alembic all behave normally on applied results.
Other add-ons: Rhea claims no namespaces beyond its own. Operators are rhea.*, node groups are RHEA_*, attributes are rhea_*, so there is nothing for another add-on to collide with.

Privacy and licensing

No network access. The extension manifest declares no network permission. Rhea cannot phone home because it has no way to.
No telemetry. Nothing is collected, counted or reported.
No licence check. No activation, no seat count, no online verification. It works offline forever.
Files written only where you ask. Presets go to the add-on directory; fabrication exports go where you point them. Nothing else is written anywhere.
Perpetual licence. One purchase. It does not expire.

Version support going forward

Rhea is tested against each new Blender release. Where an API change requires it, the fix goes into the compatibility layer and nothing else moves — that isolation is the reason support across five major versions is maintainable at all rather than becoming a slow accumulation of version checks scattered through the code.