Inspection Workbench¶

In one sentence: The Inspection workbench compares an actual object (a scan or manufactured part, represented as a mesh, point cloud, or B-rep) against one or more nominal objects (the design intent) and colours every point on the actual geometry by its signed deviation from the nominal.

What is the Inspection workbench for?¶

The Inspection workbench answers the question: "How closely does my manufactured part match the design?"

You supply:

Actual geometry — the scanned or measured object. Can be a mesh (e.g. imported from a 3-D scanner), a point cloud, or a Part solid.
Nominal geometry — the design intent. Can also be a mesh, point cloud, or Part solid.

FreeCAD computes the shortest distance from every point on the actual object to the nearest point on the nominal, stores those distances on an Inspection::Feature object, and displays a false-colour heat map directly in the 3-D view: green near zero deviation, red/blue for positive/negative deviations.

Common uses:

First-article inspection: checking that a machined part is within tolerance of the CAD model.
Reverse-engineering quality check: comparing a reconstructed surface to the original scan.
Comparing two design revisions to see what changed geometrically.
Detecting areas of a mesh that deviate from a reference shape.

Workflow overview¶

Import actual scan ──► Import nominal (CAD model)
         │                          │
         └──────────┬───────────────┘
                    ▼
         Visual Inspection dialog
         (select Actual + Nominal,
          set Search Radius)
                    │
                    ▼
         Inspection::Feature created
         (Distances list attached)
                    │
                    ▼
         Colour map displayed in 3-D view
                    │
                    ▼
         Inspect Element (pipette)
         — hover to read per-point deviation

Actual vs Nominal geometry¶

Role	Meaning	Supported types
Actual	The real, manufactured part	Mesh (MeshObject), Point cloud, Part solid
Nominal	The design intent	Mesh (MeshObject), Point cloud, Part solid

Any combination of types is supported. The most common pairing is: Actual = mesh from 3-D scanner, Nominal = Part solid from Part Design.

The distance sign convention¶

Distances are signed:

Positive — the actual point is on the outside of the nominal surface (material is proud of the design, e.g. a burr or over-material condition).
Negative — the actual point is on the inside of the nominal surface (material is missing, e.g. an undercut or under-material condition).
Zero — the actual coincides with the nominal surface.

Points farther than Search Radius from any nominal surface receive a special sentinel value (typically float::max) and are drawn in a distinct colour (usually grey) to flag them as out-of-range.

The colour bar¶

The Inspection result is visualised as a false-colour overlay:

Colour	Meaning
Green	Near-zero deviation
Red	Positive deviation (material proud)
Blue	Negative deviation (material missing)
Grey	Outside Search Radius — no valid measurement

The colour bar is visible in the 3-D view while an Inspection Feature is selected. Drag the colour bar ends to rescale the range.