Draft Studio — command-driven CAD-light

name: Draft Studio CAD overview: Ship Draft Studio (LibreCAD/AutoCAD-light) with a shared command pipeline, interchange-ready .cadjson (incl. NURBS splines) and .cadphys.json mesh/collider extension. Concept Studio unchanged; no CadKit. todos:

• id: cadjson-schemas

content: Author novolis.cad + novolis.cad.phys schemas (incl. NURBS spline, interchange fields) + examples + cadjson.md status: completed

• id: cmd-expressions

content: Add Novolis.Commands.Expressions (function-call parser + tests) in novolis-commands; map regen; publish GPR status: completed

• id: studio-command-bar

content: Add StudioCommandBar to Novolis.Avalonia.Studio; publish GPR status: completed

• id: draft-scaffold

content: Scaffold DraftStudio WinExe (csproj, DI, StudioChrome, settings/workspace paths, slnx) status: completed

• id: draft-doc-commands

content: DraftDocument load/save .cadjson + IDraftCommand bus (Line/Circle/Rect/Spline/Box/Move/Delete/Undo/Redo) from DSL + tools status: completed

• id: draft-viewport

content: 2D DraftViewport (pan/zoom/grid/snap/select) + ToolController (incl. spline fit points) emitting same commands status: completed

• id: draft-3d

content: "Model view via Avalonia.Raylib: solids + sketch on ground plane; Fit/orbit" status: completed

• id: cadphys-export

content: Optional v1 export of .cadphys.json (tessellate primitives → meshes + matching colliders) status: completed

• id: draft-release

content: Installer/CI catalog + docs; nuget-only / project-ref verification status: completed isProject: false

Decisions (locked)

Product shape (v1)

In scope

• 2D drafting as primary mode (plan/XZ plane, Vector3 with Y = 0 per library-boundaries)
• Sketch entities including spline (NURBS curve on disk; tool may collect fit points and bake control/knot data on commit)
• Light 3D model mode: solids (Box, Cylinder, Sphere) + sketch entities drawn on the ground plane
• Command bar: type Line(0,0,1,0), Circle(0,0,5), Spline(...), Box(1,1,1), Undo, Delete, …
• Interactive tools: Line / Circle / Rect / Spline (or type verb with no args) → prompt for points; finished gesture builds the same command as the typed form
• Grid + snap, pan/zoom, entity selection, undo/redo stack
• Persist as `.cadjson` under %LocalAppData%\Novolis\Draft Studio\ — format kept interchange-ready (not a minimal toy dump)
• Export (or sidecar write) `.cadphys.json` for mesh + collider consumers
• StudioChrome shell, Inno/CI catalog entry like other apps

Out of scope (v1)

• Constraint solver, parametric history, CSG, NURBS surfaces / solids (curves yes; BREP/STEP writer no)
• Shipping DXF/DWG/glTF/STEP exporters in v1 (format must still carry enough data that a later converter is not guesswork)
• Serializing CompiledScene / BVH / GPU buffers
• Sharing code with Concept Studio via ProjectReference
• Replacing Concept Studio
• Migrating Concept Studio off concept.json (optional later; formats designed so it can)

flowchart LR
  subgraph ui [DraftStudio Avalonia]
    Bar[StudioCommandBar]
    Tools[Mouse tools]
    View2D[Draft viewport 2D]
    View3D[Raylib model view]
  end
  subgraph pipe [Command pipeline]
    Dsl[FunctionCallParser]
    Cmd[DraftCommand]
    Doc[CadDocument]
  end
  subgraph formats [On disk]
    Cad[".cadjson novolis.cad"]
    Phys[".cadphys.json novolis.cad.phys"]
  end
  Bar --> Dsl
  Tools --> Cmd
  Dsl --> Cmd
  Cmd --> Doc
  Doc --> View2D
  Doc --> View3D
  Doc --> Cad
  Doc --> Phys

Document standards

Authoritative schemas live in `novolis-governance/schemas/cad/` (cross-repo contract; same role as registry schemas). Draft Studio implements load/save against them. No CadKit NuGet — optional thin C# DTOs stay app-local until a second consumer needs a shared package.

Shared conventions (both formats)

Do not put in either file: CompiledScene, BVH, material runtime graphs, workspace manifests (workspace.json stays separate).

Interchange readiness (anti–data-poor)

v1 does not ship DXF/glTF/STEP writers, but the on-disk model must not force converters to invent geometry or frame conventions. Design bar:

Rule: Sketch/solids stay analytic in .cadjson. Tessellation is derived into .cadphys.json (or at draw time). Fit-point editing UI may exist, but commit to disk must store evaluable NURBS (or both fitPoints + derived NURBS), not only opaque polylines.

1. `novolis.cad` — file extension `.cadjson`

Purpose: Authoring description of 2D sketch + 3D solid objects (parametric / constructive), layers, styles, optional view state — rich enough for later interchange.

Top-level

{
  "format": "novolis.cad",
  "schemaVersion": 1,
  "name": "Untitled",
  "generator": { "name": "DraftStudio", "version": "2026.1.0" },
  "createdAt": "2026-07-28T20:00:00Z",
  "modifiedAt": "2026-07-28T20:00:00Z",
  "unitScaleMeters": 1,
  "linearUnit": "meter",
  "angleUnit": "radian",
  "coordinateSystem": {
    "handedness": "right",
    "upAxis": "y",
    "forwardAxis": "z"
  },
  "layers": [
    { "id": "…", "name": "0", "visible": true, "locked": false, "color": [0.8, 0.8, 0.8] }
  ],
  "linetypes": [
    { "name": "Continuous" },
    { "name": "Dashed", "pattern": [6, -3] }
  ],
  "entities": [],
  "camera": {
    "yaw": 0.9,
    "pitch": 0.35,
    "distance": 40,
    "target": [0, 1, 0]
  },
  "properties": {}
}

Entity common fields: id, name?, layerId?, parentId?, kind, optional style, optional properties.

`style` (CAD stroke metadata):

Entity kinds

Optional visual on solids: material (preset string), color: number[3].

`spline` entity (NURBS curve)

Aligns with DXF SPLINE / STEP curve data so exporters do not approximate from polylines.

UI may collect fit points (Spline tool), then on commit compute degree/controlPoints/knots/weights (or store both). Display may tessellate; file of record remains NURBS.

Example sketch + spline + solid

{
  "format": "novolis.cad",
  "schemaVersion": 1,
  "name": "Hull blockout",
  "generator": { "name": "DraftStudio", "version": "2026.1.0" },
  "linearUnit": "meter",
  "angleUnit": "radian",
  "unitScaleMeters": 1,
  "coordinateSystem": { "handedness": "right", "upAxis": "y", "forwardAxis": "z" },
  "layers": [{ "id": "a0000000-0000-4000-8000-000000000001", "name": "0", "visible": true, "locked": false }],
  "linetypes": [{ "name": "Continuous" }],
  "entities": [
    {
      "id": "a0000000-0000-4000-8000-000000000010",
      "kind": "line",
      "layerId": "a0000000-0000-4000-8000-000000000001",
      "name": "keel",
      "style": { "linetype": "Continuous", "lineWeightMm": 0.25 },
      "a": [0, 0, 0],
      "b": [0, 0, 12]
    },
    {
      "id": "a0000000-0000-4000-8000-000000000012",
      "kind": "spline",
      "name": "sheer",
      "degree": 3,
      "closed": false,
      "controlPoints": [[0, 0, 0], [2, 0, 3], [2, 0, 9], [0, 0, 12]],
      "knots": [0, 0, 0, 0, 1, 1, 1, 1],
      "weights": [1, 1, 1, 1],
      "fitPoints": [[0, 0, 0], [2, 0, 6], [0, 0, 12]]
    },
    {
      "id": "a0000000-0000-4000-8000-000000000011",
      "kind": "box",
      "name": "hull",
      "center": [0, 1, 6],
      "halfExtents": [2, 1, 6],
      "material": "hull",
      "color": [0.72, 0.35, 0.28]
    }
  ]
}

Maps to: Draft Studio document; Concept Studio ConceptDocument is a subset of solids/groups (migration path later). Tessellation stays at compile time for rendering / phys export.

Schema file: `novolis-governance/schemas/cad/novolis.cad.schema.json`

2. `novolis.cad.phys` — file extension `.cadphys.json`

Purpose: Extension of novolis.cad that adds explicit triangle meshes and colliders for rendering/physics consumers. Same entity tree may be inlined (superset document) or referenced.

Extension rules

1. Every .cadphys.json is a valid novolis.cad document plus required extension fields below (same entities / layers / header conventions).
2. format must be "novolis.cad.phys" (not "novolis.cad").
3. schemaVersion is independent per format (both start at 1).
4. Optional baseDocument: relative path to a .cadjson when the phys file is a sidecar that only carries meshes/colliders + entity id bindings (entities may be omitted if baseDocument is set; loaders merge).

Additional top-level

{
  "format": "novolis.cad.phys",
  "schemaVersion": 1,
  "name": "Hull blockout",
  "unitScaleMeters": 1,
  "upAxis": "y",
  "baseDocument": "hull.cadjson",
  "meshes": [],
  "colliders": [],
  "entities": []
}

`meshes[]` — maps 1:1 toward `TriangleMesh` / StaticTriangleMesh (and later glTF primitives)

`colliders[]` — shapes separate from visual mesh (may share mesh id)

Example (sidecar style)

{
  "format": "novolis.cad.phys",
  "schemaVersion": 1,
  "name": "Hull blockout",
  "unitScaleMeters": 1,
  "upAxis": "y",
  "baseDocument": "hull.cadjson",
  "meshes": [
    {
      "id": "b0000000-0000-4000-8000-000000000001",
      "entityId": "a0000000-0000-4000-8000-000000000011",
      "name": "hull-mesh",
      "space": "local",
      "winding": "ccw",
      "vertices": [[-2, -1, -6], [2, -1, -6], [2, 1, -6], [-2, 1, -6]],
      "indices": [0, 1, 2, 0, 2, 3]
    }
  ],
  "colliders": [
    {
      "id": "c0000000-0000-4000-8000-000000000001",
      "entityId": "a0000000-0000-4000-8000-000000000011",
      "kind": "box",
      "center": [0, 1, 6],
      "halfExtents": [2, 1, 6],
      "body": { "mass": 1, "inertiaDiagonal": [1, 1, 1], "kinematic": false }
    }
  ]
}

Pipeline: .cadjson → (tessellate / export) → .cadphys.json → Math TriangleMesh + Physics colliders. Never write CompiledScene.

Schema file: `novolis-governance/schemas/cad/novolis.cad.phys.schema.json`

Also add short doc: `novolis-governance/docs/cadjson.md` linking both schemas + examples under schemas/cad/examples/.

flowchart TB
  Cad[".cadjson novolis.cad"]
  Phys[".cadphys.json novolis.cad.phys"]
  TM[TriangleMesh]
  Col[Colliders]
  Scene[SceneBuilder then CompiledScene]
  Cad -->|"extends / tessellate"| Phys
  Phys --> TM
  Phys --> Col
  Cad -->|"parametric tessellate in app"| Scene
  TM -->|"optional MeshInstance"| Scene

Where fundamentals go

App architecture

Scaffold mirrors Concept Studio bootstrap under src/DraftStudio/:

• Models/ — DTOs matching novolis.cad / optional phys export DTOs
• Commands/ — IDraftCommand + bus; factories from DSL and tools
• Services/DraftSession.cs — load/save .cadjson
• Services/CadPhysExporter.cs — tessellate solids → meshes + default matching colliders
• Services/DraftSceneBridge.cs — document → Raylib / 2D paint
• Ui/DraftViewport.cs, Ui/ToolController.cs, MainWindow.cs

Command surface (v1)

Ambiguous Line / Spline with no args → enter tool. Parser errors → StudioFeedback.

Packaging and publish order

1. Land schemas + cadjson.md in novolis-governance (no NuGet required for contracts)
2. Novolis.Commands.Expressions → map regen → GPR
3. StudioCommandBar → GPR
4. DraftStudio app + installer/CI/docs (PackageReference only)
5. Policy checks: verify-nuget-only.ps1 + verify-project-ref-mode.ps1

Explicit non-goals for this plan

• Editing Concept Studio’s REPL or forcing migration off concept.json in v1
• Shipping DXF/DWG/glTF/STEP exporters in v1 (schemas stay converter-ready)
• NURBS surfaces / BREP / boolean solids
• In-repo shared library between DraftStudio and ConceptStudio
• Formal C# shared DTO package until a second product needs it
• Storing sketch geometry as tessellated polylines only (forbidden — use analytic + NURBS)