One document, three workspaces (CAD / Modeling / Preview)

name: Hard-surface CAD toolkit overview: Pivot Novolis.Avalonia.Cad to one document with three workspaces (CAD / Modeling / Preview) on a shared scene hierarchy, staged evaluation caches, and layered generators vs mesh modifiers vs preview effects — without commercial B-rep or product-brand wording. todos:

• id: workspace-shell

content: CadWorkspace enum CAD|Modeling|Preview; replace Draft/Model dual with three modes; shared CadSceneTree + view-specific toolbars/properties/selection modes status: completed

• id: scene-graph

content: Typed SceneNode categories (Group, Geometry, Generator, MeshModifier, Material, Light, Camera, Transform); explicit operand roles; ParentId hierarchy walker status: completed

• id: staged-eval

content: CadEvaluator with cached stages (CAD solids → tessellate → mesh modifiers → transforms/instances → preview); MeshFromSolid linked|detached|baked status: completed

• id: cad-generators

content: Evaluate boolean; add Symmetry, Array/Cloner, Connect, Split Solid; wire existing instance/arrayInstance; schema + session actions status: completed

• id: mesh-modifiers

content: EditableMesh + modifier stack (Tessellate, Weld, Optimize, Bridge); Math.Geometry kernels; Modeling selection (face/edge/vertex) status: completed

• id: preview-layer

content: Preview workspace materials/lights/cameras/visibility on same tree; invalidate only appearance stage; session + property panels status: completed

• id: schema-verify

content: Extend cadjson for nodes/roles/meshFromSolid/modifiers; unit + DraftStudio smoke across three workspaces; GPR Math then Avalonia.Cad status: completed isProject: false

Pivot from prior plan

Previous plan treated hard-surface ops as a flat toolkit on entity CAD-light. New spine: one persistent model, one shared hierarchy, three workspace lenses. Ops still land in layers (CAD generators vs Modeling modifiers vs Preview effects), not one mega-geometry type.

Product wording: CAD / Modeling / Preview only — no Cinema 4D / Calypso branding in UI or docs for this feature.

Reality check (unchanged base)

Today:

• Flat `CadEntity` list; ParentId unused as a real tree
• UI is Draft | Model only (`CadEditorSurface`, `CadViewMode`)
• Schema stubs: boolean / weld / instance / arrayInstance — not evaluated; renderer skips them
• Tessellation: `CadPhysExporter`; mesh math: `TriangleMesh`
• Session mutations via `CadSessionService.Execute`
• Shapes/materials are thin (shapeId, string Material); document has a single orbit `CadCamera` — not a scene light/camera graph

Locked geometry policy: analytic CSG feature tree for CAD solids (no commercial B-rep NuGet). Tessellate explicitly via Mesh From Solid adapter. Mesh modifiers never silently destroy the CAD source.

flowchart LR
  subgraph doc [One CadDocument]
    Tree[Shared scene hierarchy]
  end
  subgraph views [Workspaces]
    Cad[CAD]
    Mod[Modeling]
    Prev[Preview]
  end
  Tree --> Cad
  Tree --> Mod
  Tree --> Prev
  Cad -->|"exact solids"| Eval1[CAD eval cache]
  Eval1 -->|"MeshFromSolid"| Eval2[Mesh + modifier cache]
  Eval2 --> Eval3[World scene cache]
  Eval3 --> Eval4[Preview image]

User-facing shell

Top-level workspaces (replace Draft/Model toggle):

[ CAD ] [ Modeling ] [ Preview ]

Shared left: scene tree (same nodes, view-filtered projection). Center: viewport. Right: properties for the active workspace. Toolbars and selection semantics swap with workspace.

Map existing Draft → CAD plan/sketch viewport; existing Model Raylib host → shared 3D host used by Modeling + Preview (different overlays/tools), or Preview starts as Model host + material/light chrome.

setviewmode expands to cad | modeling | preview (keep draft/model aliases briefly for session compat).

Shared hierarchy, different projections

One graph; each view projects different child meanings and property panels.

Door Assembly                    (Group)
├── Frame                        (Group)
│   ├── Rectangle Sketch         (CAD — CAD view)
│   ├── Extrude                  (Generator — CAD)
│   └── Bevel                    (Generator — CAD)
├── Door Leaf                    (Group)
│   ├── Mesh From Solid          (adapter — Modeling)
│   │   └── Door Body            (Geometry / CAD solid)
│   └── Weighted Normals         (MeshModifier stack)
│       └── Optimize
│           └── Weld
└── Hinge Array                  (Generator)
    └── Hinge                    (source)

CAD projection hides mesh-modifier stacks (or collapses to “has mesh”). Modeling shows CAD leaves as read-only sources under Mesh From Solid. Preview shows material/light/animation attachments on the same assemblies.

Node categories (explicit roles)

public abstract record SceneNode(Guid Id, string Name, Guid? ParentId);

public sealed record GroupNode(...) : SceneNode;
public sealed record GeometryNode(...) : SceneNode;       // solid or mesh result
public sealed record GeneratorNode(...) : SceneNode;      // boolean, array, symmetry, extrude…
public sealed record MeshFromSolidNode(...) : SceneNode;  // adapter
public sealed record MeshModifierNode(...) : SceneNode;   // weld, optimize, bridge…
public sealed record MaterialNode(...) : SceneNode;
public sealed record LightNode(...) : SceneNode;
public sealed record CameraNode(...) : SceneNode;
public sealed record TransformNode(...) : SceneNode;

Do not rely on child order alone. Structural generators use named roles (persist as fields or role-tagged links):

Boolean Difference
├── Target: Wall
└── Cutter: Door Opening

Internally keep object hierarchy and geometry processing stack distinct even if the tree UI unifies them visually.

Mesh From Solid (never silent destroy)

public sealed record MeshFromSolidNode(
    Guid SourceSolidId,
    TessellationOptions Tessellation,
    MeshLinkMode LinkMode);

public enum MeshLinkMode
{
    Linked,    // regenerates when CAD source changes
    Detached,  // independent polygon copy
    Baked      // frozen snapshot
}

Modeling ops attach above this adapter as a modifier stack, not by overwriting the CAD body.

Operation layers

CAD generators (exact)

Primitive, Sketch, Extrude, Revolve, Sweep, Boolean, Fillet, Chamfer, Array, Symmetry, Split Solid, Connect (group/compound/fuse), Instance.

v1 priority (reuse prior op order inside CAD): Boolean evaluate → Symmetry → Array/Cloner → Connect → Split by plane. Extrude/revolve/sweep/fillet/chamfer remain on the same generator API but ship in later PRs unless already trivial.

Modeling modifiers (topology)

Tessellate (via adapter), Bridge, Weld, Optimize, then Inset / Face Extrude / Loop Cut / Dissolve / Smooth / Subdivision / Normal / UV (after Bridge).

Weld/Optimize are stack modifiers on one mesh input — not multi-child assembly ops (unlike Boolean/Array).

Preview effects (appearance)

Material, Texture/Shader, Displacement (render-only vs baked-in-Modeling made explicit), Light, Camera, Fog, Visibility, Animation, Post, Render settings.

Staged evaluation + invalidation

CAD evaluation          → exact solids cache
Mesh generation         → polygons (MeshFromSolid)
Modeling modifiers      → renderable mesh cache
Transforms / instances  → world-space scene cache
Materials / lights / cam → Preview image

Invalidate narrowly:

Commands still mutate the document graph via CadCommandBus / session Execute; evaluators rebuild caches — UI never writes vertex buffers directly.

Package split

Cad already references Math.Geometry. No local feeds.

Persistence mapping

Keep one .cadjson (plus existing phys/shape sidecars). Evolve entities toward typed nodes:

Document camera may become the active Preview camera node while keeping a default for orbit bootstrap.

UI components to add (in Cad package)

1. `CadWorkspaceBar` — CAD | Modeling | Preview
2. `CadSceneTree` — shared tree, role icons, view filter, drag reparent (groups)
3. `CadToolStrip` — workspace-specific tools (CAD generators vs Modeling modifiers vs Preview place-light/camera)
4. `CadPropertyPanel` — selection + active workspace fields
5. `CadSelectionModeBar` — Object/Body/Sketch vs Object/Face/Edge/Vertex vs Object/Material/Light/Camera
6. Viewport hosts: plan sketch for CAD; Raylib for Modeling + Preview (Preview adds gizmo overlays for lights/cameras)

Wire all through session actionIds for LLM parity (setworkspace, setselectionmode, generator/modifier/preview actions).

Delivery slices (PRs)

1. Workspace shell + scene tree — CadWorkspace, tree from ParentId/groups, property stub, session setworkspace; Draft→CAD, Model→Preview interim; Modeling mode shell
2. Staged evaluator + MeshFromSolid — CAD tessellate cache, Linked/Detached/Baked, renderer consumes eval cache; stop skipping evaluated boolean once CSG works
3. CAD generators — Boolean roles, Symmetry, Array/Cloner instances, Connect, plane Split
4. Modeling modifiers — EditableMesh, Weld, Optimize, Bridge (equal loops); Modeling selection modes
5. Preview layer — material/light/camera nodes, appearance-only invalidation, Preview property panel
6. Schema/docs + verify — cadjson + cadjson.md; unit tests per stage; DraftStudio smoke across three workspaces; GPR Math then Avalonia.Cad

Explicit non-goals (near term)

• Commercial B-rep kernel
• Full sculpt / advanced subdiv / animation timeline in first Preview slice
• Merging SketchControl into CAD sketch (CAD sketch stays cadjson line/circle/rect/spline for now)
• Three separate apps or three file formats

Verification

• Unit: evaluator invalidation matrix; MeshFromSolid link modes; weld/optimize/bridge; boolean/symmetry/array
• Smoke: CAD build door-like assembly → Modeling Mesh From Solid + Weld → Preview material → change material without retessellating; edit CAD sketch with Linked mesh regenerates
• Policy scripts + ProjectRef; publish order Math → Avalonia.Cad