Direct vs. Parametric Modeling#

Vision#

We provide both modeling paradigms:

• Direct modeling (like SketchUp) — for architects, quick concept work
• Parametric modeling (like Fusion 360) — for mechanical engineers, precise constraint-driven design

Direct Modeling (v0.1–v0.2)#

Implemented features:

• Primitive creation (cube, sphere, cylinder, torus)
• Boolean operations (union, subtract, intersect)
• Gizmo-based translate transform (click-drag)
• Undo/redo with Automerge CRDT op log
• Scene save/load as JSON B-Rep
• Collaborative editing via Automerge + BroadcastChannel

Parametric Modeling (v0.3 — Current)#

Constraint Solver: ezpz#

We use KittyCAD/ezpz as the 2D geometric constraint solver.

• Language: Pure Rust, WASM-compatible
• What it does: Takes a set of geometric constraints and solves positions/dimensions
• Constraints implemented: fixed, horizontal, vertical, distance, H/V-distance, coincident, parallel, perpendicular, equal length, midpoint
• Solver: Newton-Raphson (Gauss-Newton with Tikhonov regularization)
• Local path: .src/ezpz/kcl-ezpz (Cargo path dependency)
• Integration: Wrapper types in sketch.rs bridge serde-serializable sketch types to ezpz’s non-serde internal types

Parametric Workflow#

Sketch Plane → Points + Edges → Constraints → Solver → Extrude → 3D B-Rep Solid

1. Sketch plane: User selects XY, XZ, or YZ plane
2. 2D profile: Add points with (x, y) coordinates, connect with edges
3. Constraints: Add geometric constraints (fixed, distance, horizontal, etc.)
4. Solver: ezpz solves the constraint system, returns solved positions
5. Closed loop: Edge graph is walked to find a polygon boundary
6. Extrude: truck’s tsweep sweeps the 2D face along the plane normal
7. Automerge: sketch_extrude op stores full sketch JSON for collaborative replay

Quick Rectangle#

One-click helper creates a fully constrained rectangle:

• 4 points at (0,0), (w,0), (w,h), (0,h)
• 4 edges forming a closed loop
• 7 constraints: fixed origin, 2 horizontal edges, 2 vertical edges, 2 distance constraints

Integration Points#

What’s Next#

• Arc/circle entities — curved sketch geometry
• Revolve — rsweep for rotational sweeps
• Face-based sketch planes — sketch on existing solid faces
• Feature tree UI — visual history with re-evaluation