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Glossary

Terms as this add-on uses them. Where a word means something different in Blender than it does in CAD, that difference is called out — those are the ones that cause confusion.

Core concepts

B-Rep (Boundary Representation)
How the kernel describes a solid: exact surfaces, edges and vertices with mathematical definitions, not triangles. A cylinder is a cylinder, at any zoom level. STEP export writes B-Rep; Bake to Mesh throws it away.
Kernel
The geometry engine — OpenCASCADE (OCCT) — running as a separate process alongside Blender. Everything you see in the viewport is a picture of what it computed. See How it works.
Proxy
The lightweight Blender object that stands in for a Feature Tree entry. It carries position, rotation and scale, and it is what you select and move with G / R / S. It is not the geometry.
Non-destructive
A shape stays editable after you make it. A box created twenty operations ago is still a box with a width you can retype. The opposite of Blender's mesh modelling, where the box stops being a box the moment you edit it.
Tessellation
Converting an exact surface into triangles so it can be drawn. Controlled by Linear and Curvature. It affects display and baking only, never STEP export. See Quality and performance.

The tree

Feature Tree
The ordered list of operations that produces the model. Evaluated top to bottom. It is the model; the viewport is its result. See The Feature Tree and parts.
Entry / Feature / Primitive
One row of the Feature Tree. All three words appear in the interface and mean the same thing. "Primitive" is the internal name and shows up in a few button tooltips even for things that are not primitive shapes, like Fillet.
Operation
How an entry combines with everything above it: Base, Add (Fuse), Subtract (Cut) or Intersect (Common).
Rollback point
The pin. Evaluation stops at that row; everything below is ignored.
Part
One independent Feature Tree, one Blender collection. Only the active part is evaluated. Not to be confused with a "part" in the manufacturing sense, though they usually coincide.
Group
A Group ( / Group ) pair. Entries between them combine with the rest of the model as a single unit rather than one at a time.
Target
What an entry acts on. Patterns and sweeps target another entry, by UUID. Modifiers target specific faces or edges, picked in Selection Mode.
Face and edge identity
The kernel's internal reference to a specific face or edge. Fillet stores an identity, not coordinates, which is why it survives when you change a dimension earlier in the tree — and why Cleanup (Unify) can break it.

Operations

Fillet / Chamfer
Rounding an edge / cutting it flat. Both exist twice: in 3D under Modify & Pattern, and in 2D on sketch corners. They are different operations with the same names.
Draft
Tapering a face by an angle, as needed for moulding. Requires two selections: the Neutral Plane that does not move, and the Faces to Taper that tilt.
Shell
Hollowing a solid to a wall thickness. Faces to Remove become the openings.
Inset / Offset
Insetting takes a face inwards within its own boundary; offsetting moves a face along its normal.
Loft
Blending between two or more profiles. Face Loft does the same between selected faces of existing solids.
Sweep
Running a profile along a path.
Revolve
Rotating a profile around an axis.
Cleanup (Unify)
Merging coplanar faces to simplify topology. Deliberately manual, because merging destroys face identities. A final step before export, not a mid-history one.
Instance / Link
A copy that shares the source body rather than duplicating it.
Independent
A toggle on patterns. It decides whether the pattern's own transform stacks on top of the source shape's transform or replaces it.

Sketching

Constraint
A rule the solver must satisfy — distance, parallel, tangent, and so on. You draw roughly, then constrain.
GCS (Geometric Constraint Solver)
The component that finds positions satisfying all the constraints at once.
Construction geometry
Lines kept for reference — to constrain against, to mirror about — that are not built into the resulting shape.
Over-constrained
More constraints than the geometry has freedom for, so the sketch stops moving the way you expect. The constraint list is where you find the culprit.
Inference
The temporary dotted guide shown when your cursor lines up with an existing point.
Island
One closed region of a sketch. A sketch with three separate closed loops produces three Feature Tree entries.

Output

Bake
Converting the CAD result to an ordinary Blender mesh. A snapshot — it does not stay linked.
STEP
The neutral CAD exchange format. Export is AP214 IS, and carries part names and assembly structure. Colours are not written.
AP214
The STEP application protocol used for export. Recipients occasionally ask which one; this is the answer.

See also