BestFitPlane Beta

What it does

Three points define a plane — but on a 3D scan every single point carries noise, so a three-point plane is as wrong as the three points you happened to hit. This one averages over everything you selected.

• Click the face, not the points: One click on a mesh grows a region from the clicked triangle outwards — and stops on its own where the surface turns away. Neighbouring walls and fillets stay out, so you select a face, not a blob of triangles
• Mix mesh and solid in one selection: Several clicks on one or more meshes, plus B-Rep faces of solids and surfaces — all points go into one pool and one common plane comes out
• Outliers get thrown out, not averaged in: RANSAC first, least squares after. The threshold defaults to 2.5 × robust sigma (MAD) of the residuals, so a few stray points do not tilt the result — or set a fixed distance yourself
• See the fit before you commit: Inliers green, outliers red, the plane as a blue square with its normal. The result box gives point count, inlier ratio, RMS and maximum deviation — so you know how well the plane sits before clicking OK
• A real parametric plane: Not a dead one-off. The plane lands in the timeline as a base feature and can carry sketches, joints and offsets like any other construction plane. Optionally with a sketch on it, already holding the bounding rectangle of the inliers

How to use it

1. Run Best-Fit Plane from Solid → Construct
2. Click the mesh where the plane belongs, and/or pick B-Rep faces
3. Mesh: radius (default 20 mm) limits how far a region may spread around the click
4. Mesh: normal tolerance (default 10°) decides when growing stops — lower it if fillets creep in, raise it for noisy scans
5. Check the numbers, then OK

The underlying math — welding, smoothed normals, region growing, RANSAC, least squares with a Jacobi eigensolver — is plain Python without numpy and is covered by its own test suite: synthetic scans with 20 % outliers, an adjoining 90° wall, a fillet, and 0.2 mm vertex spacing with 30 µm noise. The plane stays within 0.1° of truth and the region never eats into wall or fillet.

Installation

BestFitPlane is an add-in (not a plugin bundle) and goes into the AddIns folder:

macOS

1. Quit Fusion 360
2. Unzip and copy the BestFitPlane folder to
   ~/Library/Application Support/Autodesk/Autodesk Fusion 360/API/AddIns/
3. Start Fusion 360 — enable the add-in under Utilities → Add-Ins

Windows

1. Quit Fusion 360
2. Unzip and copy the BestFitPlane folder to
   %APPDATA%\Autodesk\Autodesk Fusion 360\API\AddIns\
3. Start Fusion 360 — enable the add-in under Utilities → Add-Ins