Pascal Editor

A 3D building editor built with React Three Fiber and WebGPU.

https://github.com/user-attachments/assets/8b50e7cf-cebe-4579-9cf3-8786b35f7b6b

Run the Editor Locally

Node.js 22.13 or newer can create a persistent local Pascal installation without cloning this repository:

npx @pascal-app/cli editor

The CLI starts the editor and an authenticated MCP service in the background, selects collision-free loopback ports, and keeps projects in ~/.pascal/data/pascal.db. Configure an agent to launch pascal mcp connect. See Run Pascal locally for pnpm/Bun commands, project management, MCP setup, updates, storage paths, and troubleshooting.

Using Published Packages

The viewer runtime and built-in node definitions are separate packages. Install the full built-in viewer set, then load the built-in plugin once before mounting <Viewer>:

npm install @pascal-app/core @pascal-app/viewer @pascal-app/editor @pascal-app/nodes

import { loadPlugin } from '@pascal-app/core'
import { builtinPlugin } from '@pascal-app/nodes'

await loadPlugin(builtinPlugin)

See the @pascal-app/viewer quick start for a React example.

Repository Architecture

This is a Turborepo monorepo with the reusable editor packages, the standalone app, and the CLI that distributes it:

editor/
├── apps/
│   └── editor/          # Next.js application
├── packages/
│   ├── core/            # Schemas, scene state, and registry contracts
│   ├── viewer/          # 3D rendering runtime and shared systems
│   ├── editor/          # Editing tools and UI components
│   ├── nodes/           # Built-in node definitions, renderers, and systems
│   ├── cli/             # Persistent local editor installer and process manager
│   ├── mcp/             # Model Context Protocol server and scene storage
│   └── ui/              # Shared UI components

Separation of Concerns

| Package | Responsibility | |---------|---------------| | @pascal-app/core | Node schemas, scene state (Zustand), registry contracts, spatial queries, and event bus | | @pascal-app/viewer | 3D rendering via React Three Fiber, shared render systems, default camera/controls, and post-processing | | @pascal-app/editor | Editing tools, panels, selection, and direct-manipulation UI | | @pascal-app/nodes | Built-in registry plugin with node definitions, renderers, geometry, and systems | | @pascal-app/cli | Installs and manages a versioned standalone editor runtime and persistent local data | | @pascal-app/mcp | Exposes scene tools, resources, prompts, and local storage to MCP-compatible AI hosts | | apps/editor | Standalone Next.js host for the editor packages |

The viewer renders the scene with sensible defaults. The editor extends it with interactive tools, selection management, and editing capabilities.

Stores

Each package has its own Zustand store for managing state:

| Store | Package | Responsibility | |-------|---------|----------------| | useScene | @pascal-app/core | Scene data: nodes, root IDs, dirty nodes, CRUD operations. Persisted to IndexedDB with undo/redo via Zundo. | | useViewer | @pascal-app/viewer | Viewer state: current selection (building/level/zone IDs), level display mode (stacked/exploded/solo), camera mode. | | useEditor | apps/editor | Editor state: active tool, structure layer visibility, panel states, editor-specific preferences. |

Access patterns:

// Subscribe to state changes (React component)
const nodes = useScene((state) => state.nodes)
const levelId = useViewer((state) => state.selection.levelId)
const activeTool = useEditor((state) => state.tool)

// Access state outside React (callbacks, systems)
const node = useScene.getState().nodes[id]
useViewer.getState().setSelection({ levelId: 'level_123' })

---

Core Concepts

Nodes

Nodes are the data primitives that describe the 3D scene. All nodes extend BaseNode:

BaseNode {
  id: string              // Auto-generated with type prefix (e.g., "wall_abc123")
  type: string            // Discriminator for type-safe handling
  parentId: string | null // Parent node reference
  visible: boolean
  camera?: Camera         // Optional saved camera position
  metadata?: JSON         // Arbitrary metadata (e.g., { isTransient: true })
}

Node Hierarchy:

Site
└── Building
    └── Level
        ├── Wall → Item (doors, windows)
        ├── Slab
        ├── Ceiling → Item (lights)
        ├── Roof
        ├── Zone
        ├── Scan (3D reference)
        └── Guide (2D reference)

Nodes are stored in a flat dictionary (Record<id, Node>), not a nested tree. Parent-child relationships are defined via parentId and children arrays.

---

Scene State (Zustand Store)

The scene is managed by a Zustand store in @pascal-app/core:

useScene.getState() = {
  nodes: Record<id, AnyNode>,  // All nodes
  rootNodeIds: string[],       // Top-level nodes (sites)
  dirtyNodes: Set<string>,     // Nodes pending system updates

  createNode(node, parentId),
  updateNode(id, updates),
  deleteNode(id),
}

Middleware:

• Persist - Saves to IndexedDB (excludes transient nodes)
• Temporal (Zundo) - Undo/redo with 50-step history

---

Scene Registry

The registry maps node IDs to their Three.js objects for fast lookup:

sceneRegistry = {
  nodes: Map<id, Object3D>,    // ID → 3D object
  byType: {
    wall: Set<id>,
    item: Set<id>,
    zone: Set<id>,
    // ...
  }
}

Renderers register their refs using the useRegistry hook:

const ref = useRef<Mesh>(null!)
useRegistry(node.id, 'wall', ref)

This allows systems to access 3D objects directly without traversing the scene graph.

---

Node Renderers

Renderers are React components that create Three.js objects for each node type:

SceneRenderer
└── NodeRenderer (dispatches by type)
    ├── BuildingRenderer
    ├── LevelRenderer
    ├── WallRenderer
    ├── SlabRenderer
    ├── ZoneRenderer
    ├── ItemRenderer
    └── ...

Pattern:

1. Renderer creates a placeholder mesh/group
2. Registers it with useRegistry
3. Systems update geometry based on node data

Example (simplified):

const WallRenderer = ({ node }) => {
  const ref = useRef<Mesh>(null!)
  useRegistry(node.id, 'wall', ref)

  return (
    <mesh ref={ref}>
      <boxGeometry args={[0, 0, 0]} />  {/* Replaced by WallSystem */}
      <meshStandardMaterial />
      {node.children.map(id => <NodeRenderer key={id} nodeId={id} />)}
    </mesh>
  )
}

---

Systems

Systems are React components that run in the render loop (useFrame) to update geometry and transforms. They process dirty nodes marked by the store.

Core Systems (in @pascal-app/core):

| System | Responsibility | |--------|---------------| | WallSystem | Generates wall geometry with mitering and CSG cutouts for doors/windows | | SlabSystem | Generates floor geometry from polygons | | CeilingSystem | Generates ceiling geometry | | RoofSystem | Generates roof geometry | | ItemSystem | Positions items on walls, ceilings, or floors (slab elevation) |

Viewer Systems (in @pascal-app/viewer):

| System | Responsibility | |--------|---------------| | LevelSystem | Handles level visibility and vertical positioning (stacked/exploded/solo modes) | | ScanSystem | Controls 3D scan visibility | | GuideSystem | Controls guide image visibility |

Processing Pattern:

useFrame(() => {
  for (const id of dirtyNodes) {
    const obj = sceneRegistry.nodes.get(id)
    const node = useScene.getState().nodes[id]

    // Update geometry, transforms, etc.
    updateGeometry(obj, node)

    dirtyNodes.delete(id)
  }
})

---

Dirty Nodes

When a node changes, it's marked as dirty in useScene.getState().dirtyNodes. Systems check this set each frame and only recompute geometry for dirty nodes.

// Automatic: createNode, updateNode, deleteNode mark nodes dirty
useScene.getState().updateNode(wallId, { thickness: 0.2 })
// → wallId added to dirtyNodes
// → WallSystem regenerates geometry next frame
// → wallId removed from dirtyNodes

Manual marking:

useScene.getState().dirtyNodes.add(wallId)

---

Event Bus

Inter-component communication uses a typed event emitter (mitt):

// Node events
emitter.on('wall:click', (event) => { ... })
emitter.on('item:enter', (event) => { ... })
emitter.on('zone:context-menu', (event) => { ... })

// Grid events (background)
emitter.on('grid:click', (event) => { ... })

// Event payload
NodeEvent {
  node: AnyNode
  position: [x, y, z]
  localPosition: [x, y, z]
  normal?: [x, y, z]
  stopPropagation: () => void
}

---

Spatial Grid Manager

Handles collision detection and placement validation:

spatialGridManager.canPlaceOnFloor(levelId, position, dimensions, rotation)
spatialGridManager.canPlaceOnWall(wallId, t, height, dimensions)
spatialGridManager.getSlabElevationAt(levelId, x, z)

Used by item placement tools to validate positions and calculate slab elevations.

---

Editor Architecture

The editor extends the viewer with:

Tools

Tools are activated via the toolbar and handle user input for specific operations:

• SelectTool - Selection and manipulation
• WallTool - Draw walls
• ZoneTool - Create zones
• ItemTool - Place furniture/fixtures
• SlabTool - Create floor slabs

Selection Manager

The editor uses a custom selection manager with hierarchical navigation:

Site → Building → Level → Zone → Items

Each depth level has its own selection strategy for hover/click behavior.

Editor-Specific Systems

• ZoneSystem - Controls zone visibility based on level mode
• Custom camera controls with node focusing

---

Data Flow

User Action (click, drag)
       ↓
Tool Handler
       ↓
useScene.createNode() / updateNode()
       ↓
Node added/updated in store
Node marked dirty
       ↓
React re-renders NodeRenderer
useRegistry() registers 3D object
       ↓
System detects dirty node (useFrame)
Updates geometry via sceneRegistry
Clears dirty flag

---

Building a Plugin

The editor is extensible: a plugin ships node kinds (schema, 3D/2D rendering, placement tools, inspector parametrics) and left-rail panels through the same Plugin manifest the built-ins use — there is no separate internal API.

• Developer guide — Create a plugin: the Plugin shape, panel contributions, discovery, lifecycle, and what's in/out of v1.
• Worked example — pascalorg/plugin-trees: a standalone plugin with procedural trees, flowers, grass, and a presets panel. Clone it as a starting point.

---

Technology Stack

• React 19 + Next.js 16
• Three.js (WebGPU renderer)
• React Three Fiber + Drei
• Zustand (state management)
• Zod (schema validation)
• Zundo (undo/redo)
• **thre