If you model in Onshape or SolidWorks, Rig Cad feels familiar for about ten minutes and then differs in one specific way: there is no feature timeline. Every feature is a node in a live tree, every dimension can be an expression, and blends, lattices and textures come from a signed-distance field rather than a B-rep. This guide maps your features to their Rig Cad equivalents, names what has no equivalent, and explains the one mental shift that makes the rest click.

What maps directly

Table: Feature-based CAD operations and their Rig Cad counterparts.

Onshape / SolidWorks Rig Cad Read
Sketch with dimensions and constraints 2D primitives, a path with bound points, or a Sketch 2D node with a constraint solver Sketches to Solids
Extrude, Revolve Linear Extrude, Revolve (the result is Y-up; rotate X by 90) Same
Boolean, Combine, Split Union, Difference, Intersection, Symmetric Difference, Hull; all work in 2D as well CSG
Fillet, Chamfer Primitive cornerRadius, extrude edge profiles, SDF smooth blends, Minkowski, Surface Offset Fillets and Chamfers
Shell Shell post-processing step, or a 2D inward offset plus floor Shell and Hollowing
Linear and Circular Pattern Linear Repeat, Radial Repeat, Parametric Repeat, Path Repeat Repeats and Arrays
Mirror A two-copy Linear Repeat, or the Mirror step with its local-origin rule Same
Hole wizard, Thread A cylinder cutter with a derived through-depth; the Thread node in external or internal_cut mode Threads and Snap Fits
Variables, Equations, Global Variables Project variables: typed, ranged, validated, with expressions on any node parameter Expressions and Variables
Configurations Select and boolean variables gating options.enabled and driving expressions Beyond Sliders
Part Studio with several parts Several root nodes in one project; each root is a part Editor Guide
Assembly and mates Expressions that place parts relative to each other; Assembly and Assembly Instance for reusable sub-assemblies Transforms
Interference detection The Interference check: exact intersection volume and minimum separation Threads article, above
Section view The Cross Section node, parked disabled, always current Shell article, above
Mass properties Volume, area, centre of gravity and topology in Object Properties Same
Export STL, 3MF, STEP Export Geometry: STL, 3MF, OBJ, plus GLTF, PLY, USDZ, DXF, SVG Export for the Slicer

STEP is the notable absence: Rig Cad's tree is its own source format, and the outputs are meshes and curves.

What has no equivalent, and what replaces it

The timeline. There is no feature history to roll back through. The tree is the history: a Difference above a Union means the cut happens after the join, and reordering nodes reorders the operations. Undo and redo cover editing mistakes; labelled saves cover restore points.

Face and edge selection. You cannot click an edge and fillet it, because the mesh is a result, not a source. Rounding is declared on the node that owns the edge, which is why the fillet article lists five routes instead of one tool.

Drawings. There is no drawing environment. The Cross Section node and the DXF and SVG exports cover the section-and-outline cases; dimensions live in the variables.

Mates. Parts are placed by expressions, not by constraints between faces. Nut.transform.position.z = headHeight + threadLength - nutHeight is a mate that never breaks when the bolt changes, and an Interference check proves the fit instead of a mate warning.

Lofts and surfacing. Rig Cad does not loft between profiles. Transitions between shapes are SDF blends, which are smoother than most lofts and come with blend modes, but they are volumes, not surfaces. Signed Distance Fields is the article to read before you try to recreate a surfaced part.

The mental shift: features are nodes, dimensions are expressions

In feature-based CAD you sketch, constrain, extrude, then fillet, and the history records the order. In Rig Cad you build the same part as a tree whose shape you can read top-down.

Diagram: A typical part tree. A difference at the top subtracts a hole cutter from a smooth SDF union of a rounded plate and a boss.

flowchart TD
  P["Finished_Part (difference)"] --> B["Body (union, sdf, smooth)"]
  P --> H["Hole_Cutter (cylinder, height = thickness + 2 * margin)"]
  B --> Plate["Plate (box, cornerRadius)"]
  B --> Boss["Boss (cylinder)"]

Three habits carry over from the feature world and three do not.

Carry over: name every dimension; drive features from those names; keep construction geometry separate from finished geometry. Rig Cad's variables, expressions and hidden helpers are exactly the equation-driven modelling you already do, with a validator and a readout added.

Change: the group is a Union, so a sub-assembly is a union with its own transform and the leaves stay in local coordinates; placement is an expression relative to the host, never a typed coordinate; and sharp features live above the blend group, not inside it. The mounting tab in the CSG article is the smallest complete example: three primitives, two Booleans, and a cutter depth derived from the plate thickness so the hole is always through.

The constraint solver is still there when you need it. A Sketch 2D node holds parallels, coincidences and dimensions and reports its degrees of freedom, but it is the tool for outlines that carry rules, not the default for every profile.

Interactive Sandbox
View project
A flange, a revolved cup and an offset gasket built the Rig Cad way. Expand the tree on the right: the flange is a 2D Difference of a rounded rectangle, a bore and a radial repeat of one hole, extruded once with a chamfered edge.
Sketches to solids demoInteractive Rig Cad editor

Where the browser wins

Four things are easier here than in a B-rep modeller. Smooth blends between arbitrary solids, with a choice of blend profile, are a checkbox on a Union. Lattices, foams and textures are one Pattern 3D node or an Infill step rather than a plug-in. A finished model becomes a customer-facing configurator by enabling embedding and sharing a link. And there is nothing to install, so the same project opens on any machine with a browser and, for the field evaluation, a GPU.

The cost is that mesh resolution is a setting you own. Why Is My Model Slow? is the article a feature-based CAD user should read first, because precision is the knob that has no analogue in a B-rep kernel.

Where to start

Read the Editor Guide for the five panels, then Constructive Solid Geometry in Rig Cad and Transforms and Reference Frames for the tree and its coordinate conventions. The Fusion 360 guide covers the same ground from a timeline-based tool and overlaps with this one on purpose; the OpenSCAD guide is the one to read if you already think in code.