Troubleshooting¶

Nothing computes at all¶

Open Edit > Preferences > Add-ons and expand Seamless CAD. The panel reports CAD Engine: Running or Not running, based on the real state of the kernel process rather than a fixed assumption.

If it says Not running, the kernel process failed to start or has exited. Restart Blender. If it happens repeatedly, enable Enable ERROR Logs (it is on by default) and check Blender's console output.

The Seamless tab is empty below the workspace panel¶

No valid part collection is selected. The panels below Active CAD Workspace only appear when there is one.

Pick a part from the dropdown, or press Add New CAD Part.

Panels disappeared and I see "Sketch Mode"¶

You are in sketch mode. The normal panels are hidden while it is active. Press Apply or Cancel at the bottom of the sketch panel to leave.

A shape looks wrong while dragging, correct when released¶

That is the fast preview doing its job. Fast Modifier Preview and Live Boolean Preview show an approximation during the drag; the released result is computed exactly.

Turn them off in Quality & Export if you would rather always see the exact shape. See Quality and performance.

I have two Blenders open and one of them will not preview¶

Expected, for now. The kernel that computes geometry runs on a fixed local port, and the first Blender to start claims it. The second one connects to that same kernel instead of starting its own, so it is asking a process that holds someone else's model to draw yours.

Bake to Mesh in the file you are only using for reference, or disable the add-on there, or close one before working in the other. See Known limitations.

Nothing updates after an edit¶

Press the refresh icon in Modify & Pattern > Topology to force a full recompute.

If that fixes it consistently, the logs are worth capturing — enable Enable WARN Logs in preferences and report what you see.

Hide Occluded Edges is greyed out¶

Intentional, not a bug. Faces only write depth when Use WGPU Overlay is off and Opacity is fully opaque. In any other combination the setting has nothing to work with.

Turn off the WGPU overlay and set opacity to fully opaque, and it becomes available.

Edit Sketch is greyed out¶

The panel will say "Hidden by rollback point". The entry sits below an active rollback pin, so it is not currently being evaluated.

Click the pin icon in the Feature Tree to unpin, then edit.

A fillet or offset broke after I changed something earlier¶

Fillets, chamfers, offsets, shells and drafts refer to specific face and edge identities in the kernel's topology. Most edits preserve those identities, which is why the operations survive dimension changes. Some do not.

The usual culprit is Cleanup (Unify) somewhere above the operation in the tree — merging coplanar faces destroys the identities of the faces it merges. This is why Cleanup is manual and best kept as a final step before export. See How it works.

Reselect the targets for the affected operation to repair it.

The Distance constraint button vanished in sketch mode¶

It is only shown when the current selection can take a distance constraint and does not already have one. If it is missing, the constraint already exists.

Look at Selection Info — the existing constraint's value is editable there. For arcs it appears as Radius rather than Length.

The sketch will not move the way I want¶

Usually over-constrained. Turn on Constraints / Parameters in the sketch panel for a full list of constraints with the IDs they act on, and delete the one that is holding it. See Sketching.

Everything is slow, not just one operation¶

If the whole add-on feels slow regardless of what you do — including on hardware that should have no trouble — work through these in order:

Check for a leftover kernel process. Task Manager (Ctrl+Shift+Esc) → Details → look for cad_server.exe. If there is more than one, or one is left over from a session that crashed, close them all and restart Blender. A stale kernel keeps answering while holding the wrong state.
Turn off Use WGPU Overlay and set Opacity fully opaque. These two interact, so testing them one at a time can miss the effect. The overlay is experimental and the add-on is expected to run faster with it off.
Check whether security software is inspecting local connections. Blender and the kernel talk over a local TCP port. Software that hooks that traffic can slow every operation noticeably.
Capture a profile. Enable Perf Logging in preferences, perform the slow action once, then look at seamless_cad_profile.log in your OS temp directory. It shows where the time actually goes, which beats guessing.

When reporting it, say which of drag, release, or startup is the slow part — they are different parts of the pipeline and the answer narrows things down a lot.

Editing an early operation is slow¶

Expected. Everything below the edited operation must be recomputed, so an edit near the top of a long history costs more than one near the bottom. This is inherent to history-based CAD.

Set a rollback point just below the operation you are working on. Everything under the pin stops being evaluated until you unpin.

Dimensions came out 1000× wrong in another CAD program¶

On STEP export, 1 Blender unit is written as 1 mm. A 10-unit box arrives as 10 mm. If your scene was built assuming 1 unit = 1 m, everything will be a thousand times too small.

There is no export scale option, so the fix is to build at the right scale, or to rescale in the receiving application.

The exported STEP has no colours¶

Correct, and expected. There is nowhere in the addon to set a colour, so there is nothing for the file to carry.

Names and assembly structure are written, though. If your file arrives unnamed, check that you are exporting STEP and not IGES — IGES carries geometry only. The product name comes from the Part's collection name, so renaming the collection renames the part in the file. See Import and export.

Reporting a problem¶

Useful things to include:

Blender version, and whether the add-on was installed as a legacy add-on or as a Blender 4.2+ Extension
What CAD Engine reports in preferences
The console output with Enable WARN Logs turned on
If it is a performance problem, enable Perf Logging and attach seamless_cad_profile.log from your OS temp directory