Known limitations¶

This page is deliberately blunt. It is better to know these before you build something important than to discover them afterwards.

Beta¶

Seamless CAD is in beta. Behaviour can change between versions, and it can crash. Save often.

Windows only¶

The released product runs on Windows only, because the geometry kernel ships as a bundled executable built for Windows.

Builds for Linux (x86-64) and macOS (Apple Silicon) now exist and are being given to testers. They are not on sale and have no release date. There is no Intel Mac build. A few testers have now reported both builds running inside Blender, which is the first signal from real hardware — but how far they exercised them is not known, so it is a long way from a tested platform. See Testing builds for what has and has not been verified.

What still stands between those builds and a release is not the add-on's Python code:

macOS is not notarised. The kernel is ad-hoc signed only. Notarisation requires an Apple Developer Program membership, which is not currently funded. That is the honest reason, and it is the main obstacle to a macOS release
Almost nothing has been confirmed on real hardware. A few testers say the builds run; what works past that, including whether the viewport draws through Metal at all, is still unestablished — automated builds cannot settle it
On Linux, glibc 2.34 is the effective floor (Ubuntu 22.04, Debian 12, RHEL 9 and newer)

Blender versions¶

Blender 4.2 or newer. Development and testing happen on 5.1. Versions in between are expected to work but receive less testing.

The add-on ships as a classic add-on, not as a Blender Extension. The zip carries no blender_manifest.toml, so drag-and-drop installation and the Extensions repository do not apply — use Install from Disk…. See Installation.

The Feature Tree cannot be reordered¶

Order is creation order. Rows cannot be moved up or down, and a new operation cannot be inserted into the middle of an existing history — new entries are always appended to the end, including while a rollback pin is set.

This is a real constraint on how you work: order has to be decided as you build. The Feature Tree and parts covers what to do instead.

Exported files carry no colours¶

STEP export writes part names and assembly structure, and the geometry is exact B-Rep in AP214 IS. Colours are the one thing missing, and the reason is upstream of the exporter: there is nowhere in this addon to give a Part or a face a colour, so there is nothing for the file to carry.

If your recipient needs colour-coded assemblies, this export will not meet that need yet.

IGES export is a further step back: geometry only, with no names and no structure. That is deliberate — IGES readers disagree too much about names for them to be dependable. Use STEP unless the recipient cannot read it.

STEP export units¶

One Blender unit is written as 1 mm by default. The export dialog has a Scale (1 unit = N mm) field if you work at another scale: 1000 if a unit is a metre, 10 if it is a centimetre. It means the same thing as Import's Scale, so a file brought in at 10 goes back out unchanged at 10.

Leaving it at 1.0 keeps the behaviour of every earlier version.

Inset needs a flat face¶

Inset does nothing on a curved face — the side of a cylinder or a cone. It offsets the face's boundary inwards using an operation that assumes a plane, and on a curved surface that operation simply does not produce a result. Nothing happens and nothing is reported.

The flat ends of a cylinder or cone are fine, as is every face of a box.

A large inset on a filleted face can produce a wrong shape. Past a certain distance — the threshold depends on the model — the inward offset breaks down instead of failing cleanly. On Windows the result is geometry that is visibly wrong, and the fillet above it may disappear. On Linux and macOS the same operation used to kill the kernel outright; since 8.1.5.12 the fault is caught and a simpler method is used instead, so it no longer crashes, but the cause has not been removed.

If an inset comes out looking wrong, reduce the distance. This is a real defect, not a design limit, and a report with the model is welcome.

A fillet can refuse an edge that ends tangent to another surface¶

Some edges cannot be filleted, and the result is that nothing happens. The usual case is an edge that stops exactly where it meets a curved surface — for example a cut that runs up to the wall of a hole and ends on it. The blend has nowhere to terminate, and the geometry kernel returns a surface that runs off into space while reporting success.

The add-on checks the result and discards it when it is not plausible, so the previous shape is kept. A fillet that appears to do nothing on an edge like that has been refused, not ignored. Reducing the radius usually does not help, because the problem is the edge rather than the size.

What does help is not creating that edge in the first place — rounding the edge before the cut that makes it tangent. Today the Feature Tree cannot be reordered, so that means building in that order from the start.

Cleanup (Unify) is destructive to references¶

Merging coplanar faces destroys the face identities that Fillet, Chamfer, Offset, Shell and Draft depend on. It is not applied automatically for this reason, and applying it in the middle of a live history can break operations below it.

Treat it as a final step before export. See How it works.

Only one Blender at a time can compute geometry¶

Geometry is computed by a separate kernel process that Blender talks to over a fixed local port. The first Blender to start claims it. Open a second Blender with the add-on enabled and it will not start its own kernel — it connects to the one already running, which is holding another file's geometry. The result is that previews stop updating correctly in one or both windows.

This matters if you keep a second Blender open for reference, which is a normal way to work.

Until each Blender gets its own kernel, the ways round it are:

Bake to Mesh in the reference file, so it needs no kernel at all
Disable the add-on in the Blender you are only using to look at something
Close one Blender before starting work in the other

Nothing is corrupted by this — it is the live preview that goes wrong, not your saved data.

Baked meshes do not stay linked¶

Bake to Mesh produces a snapshot. It does not update when the Feature Tree changes; you have to bake again.

Editing early history is expensive¶

Changing an operation near the top of a long Feature Tree requires recomputing everything below it. This is inherent to history-based CAD rather than a defect, but it is a real limit on how large a single part can comfortably get.

Rollback points and splitting into multiple parts are the mitigations. See Quality and performance.

Blender mesh tools do not apply¶

CAD shapes are computed by the kernel, not by Blender's mesh system. Blender's modelling, sculpting and modifier tools cannot act on them directly. Bake to Mesh first.

Documentation coverage¶

English is complete and is the source of truth. Japanese mirrors it. Russian and Chinese are limited to the Quick Start page, and those two translations were produced by AI without review by a native speaker — they are marked as such at the top of each page.