PartHistory Reference

PartHistory lives in src/PartHistory.js and is the core modeling history manager. It owns the feature list, the shared Three.js scene, the expression scratchpad, PMI views, metadata, and the assembly constraint history. It can rebuild geometry deterministically by replaying feature entries, serialize and restore part state, and maintain undo/redo via JSON snapshots.

Live Demos

• Examples hub: https://BREP.io/apiExamples/index.html
• Embeded CAD: https://BREP.io/apiExamples/Embeded_CAD.html
• Embeded CAD Integration Test: https://BREP.io/apiExamples/Embeded_CAD_Integration_Test.html

Responsibilities

• Manage the ordered list of modeling features (features).
• Own and mutate the shared Three.js scene.
• Evaluate parameter expressions via a user-defined expression script.
• Run the history to (re)build geometry from feature inputs.
• Persist and restore feature history, PMI views, metadata, and assembly constraints.
• Track and apply undo/redo snapshots.
• Sync and update assembly component data.

Constructor

new PartHistory()

Creates a new history manager and initializes:

• features: empty array
• scene: new THREE.Scene()
• featureRegistry: new FeatureRegistry()
• assemblyConstraintRegistry: new AssemblyConstraintRegistry()
• assemblyConstraintHistory: new AssemblyConstraintHistory(this, registry)
• pmiViewsManager: new PMIViewsManager(this)
• metadataManager: new MetadataManager()
• expressions: default example script string
• callbacks: empty bag for optional hooks
• Undo/redo state in _historyUndo

The constructor also soft-overrides scene.remove and scene.add to aid debugging and to block removal of objects with userData.preventRemove.

Data model

Feature entry shape

Each entry in features is a plain object with at least:

{
  type: string,                 // Feature type string (registry key)
  inputParams: Object,          // User inputs; includes an id
  persistentData: Object,       // Saved outputs from previous runs
  timestamp?: number,           // Last run time (ms epoch)
  dirty?: boolean,              // Marks entry for re-run
  lastRunInputParams?: string,  // JSON string for dirty detection
  lastRun?: {                   // Execution metadata
    ok: boolean,
    startedAt: number,
    endedAt: number,
    durationMs: number,
    error: { name, message, stack } | null
  },
  effects?: { added: [], removed: [] },
  previouseExpressions?: Object // Cached evaluated numeric inputs
}

IDs are normalized and kept in sync:

• feature.inputParams.id and feature.id are strings.
• A non-enumerable feature.inputParams.featureID property is defined as an alias of id for legacy compatibility.

Feature class contract

A feature class (from FeatureRegistry) is expected to provide:

• static inputParamsSchema describing inputs and defaults.
• run(partHistory) which returns { added, removed }.
• Optional longName, shortName, name for display.
• (Sketch only) hasSketchChanged(feature) for dirty detection.

Result artifacts

run() should return an object with:

• added: array of objects to add to the scene
• removed: array of objects to remove from the scene

Objects are expected to be compatible with Three.js scene nodes. If they implement free() and/or visualize(), those are called automatically.

Expressions

expressions is a user-editable script string. Numeric inputs can reference it.

• Static helper: PartHistory.evaluateExpression(expressionsSource, equation)
• Instance helper: partHistory.evaluateExpression(equation)

evaluateExpression uses Function() to execute the script and return an evaluated value. It returns null on error. Treat expression input as code (do not evaluate untrusted content).

Execution flow

runHistory()

Rebuilds the scene by replaying features in order.

High-level flow:

1. Clear the scene and dispose resources, preserving lights, cameras, and transform gizmos.
2. Iterate features in order:

- Normalize ID linkage for each feature. - Stop after currentHistoryStepId (if set) but keep later features in the list. - Resolve the feature class from the registry; if missing, mark lastRun with a MissingFeature error and continue. - Copy persistentData into the feature instance. - Remove any existing scene children with owningFeatureID === featureId (rerun case). - Compute dirty state based on: - changed input params - feature timestamps vs. upstream features - newer referenced objects - expression evaluation changes - Sketch change detection - If dirty: - call run() - record lastRun, timestamp, effects, lastRunInputParams - Apply effects via applyFeatureEffects().

3. Run assembly constraints.
4. Call optional callbacks.

Notes:

• currentHistoryStepId is not cleared inside runHistory().
• Any feature error stops the run and logs the error.
• runHistory() returns this.

Scene integration and selection

When adding objects:

• applyFeatureEffects() calls free() and visualize() if present.
• Each added object and its descendants get timestamp and owningFeatureID.
• Each object gets an onClick handler that uses SelectionFilter.toggleSelection.

Objects with userData.preventRemove are not removed when the scene is cleared.

Serialization

toJSON()

Returns a pretty-printed JSON string containing:

• features (type, inputParams, persistentData, timestamp)
• idCounter
• expressions
• pmiViews (via PMIViewsManager)
• metadata (from MetadataManager)
• assemblyConstraints and assemblyConstraintIdCounter

Before export, assembly component transforms are synced into feature input params.

fromJSON(jsonString, options)

Restores state from a JSON string. Behavior:

• Migrates legacy featureID fields to id.
• Rehydrates PMI views and metadata.
• Loads assembly constraints into AssemblyConstraintHistory.
• Resets undo/redo history unless options.skipUndoReset is true.

Undo / redo

PartHistory maintains a JSON snapshot stack:

• _historyUndo.undoStack and _historyUndo.redoStack
• Debounced snapshot capture (debounceMs, default 350ms)
• Max snapshot count (max, default 50)

Key methods:

• queueHistorySnapshot({ debounceMs, force })
• flushHistorySnapshot({ force })
• undoFeatureHistory()
• redoFeatureHistory()
• canUndoFeatureHistory()
• canRedoFeatureHistory()

Undo/redo restores by calling fromJSON() and re-running runHistory().

Assembly components and constraints

• assemblyConstraintHistory owns constraints and runs the solver.
• runAssemblyConstraints() delegates to AssemblyConstraintHistory.runAll().

Assembly component utilities:

• hasAssemblyComponents(): returns true if any feature is an assembly component.
• syncAssemblyComponentTransforms(): copies scene transforms into feature input params.
• getOutdatedAssemblyComponentCount(): counts components whose source data changed.
• updateAssemblyComponents({ rerun = true }): refreshes component data and optionally re-runs history.

Public properties

• features: Array<Object>
• scene: THREE.Scene
• idCounter: number
• featureRegistry: FeatureRegistry
• assemblyConstraintRegistry: AssemblyConstraintRegistry
• assemblyConstraintHistory: AssemblyConstraintHistory
• pmiViewsManager: PMIViewsManager
• metadataManager: MetadataManager
• expressions: string

- currentHistoryStepId: string | null

• callbacks: Object (optional hooks)
• _historyUndo: Object (internal state)

Callbacks

callbacks is a simple bag of optional functions:

• callbacks.run(featureId) - called before each feature runs (awaited).
• callbacks.reset() - called after reset() clears scene (awaited).
• callbacks.afterRunHistory() - called after runHistory() completes.
• callbacks.afterReset() - called after reset() finishes.

API reference

Static

#### PartHistory.evaluateExpression(expressionsSource, equation): any | null

Evaluates equation using expressionsSource as the preamble. Returns null on error.

Instance

#### evaluateExpression(equation): any | null

Same as static helper but uses this.expressions.

#### getObjectByName(name): Object3D | null

Delegates to scene.getObjectByName.

reset(): Promise<void>

Clears features, resets managers, clears the scene, and resets undo/redo. Calls callbacks.reset and callbacks.afterReset.

runHistory(): Promise<PartHistory>

Replays features, rebuilds the scene, runs constraints, and calls callbacks.afterRunHistory.

applyFeatureEffects(effects, featureId, feature): Promise<void>

Applies added/removed artifacts to the scene, sets timestamps/ownership, and attaches selection handlers.

toJSON(): Promise<string>

Serializes the full part history and related state.

fromJSON(jsonString, options?): Promise<void>

Restores from a serialized history string.

generateId(prefix): Promise<string>

Increments idCounter and returns ${prefix}${idCounter}.

sanitizeInputParams(schema, inputParams): Promise<Object>

Normalizes and evaluates input params based on schema types:

• number: evaluates expressions
• reference_selection: resolves object names to scene objects
• boolean_operation: normalizes op and target list, optional bias/offset
• transform: evaluates position/rotation/scale arrays
• vec3: evaluates 3-vector entries
• boolean: normalizes to boolean
• default: pass-through

newFeature(featureType): Promise<Object>

Creates a new feature entry, seeds defaults from schema, assigns an ID, and appends it to features.

removeFeature(featureId): Promise<void>

Removes any feature with matching ID.

resetHistoryUndo(): void

Clears undo/redo stacks and internal flags.

queueHistorySnapshot(options?): void

Debounced snapshot capture.

flushHistorySnapshot(options?): Promise<void>

Forces a snapshot immediately.

undoFeatureHistory(): Promise<boolean>

Restores the previous snapshot if available.

redoFeatureHistory(): Promise<boolean>

Reapplies the next snapshot if available.

runAssemblyConstraints(): Promise<Array>

Runs the assembly constraint solver.

hasAssemblyComponents(): boolean

Checks if any feature is an assembly component.

syncAssemblyComponentTransforms(): void

Writes current scene transforms into feature input params.

getOutdatedAssemblyComponentCount(): number

Returns number of outdated components.

updateAssemblyComponents(options?): Promise<{ updatedCount, reran }>

Refreshes assembly component data; optionally re-runs history.

Internal helpers

These methods are intended for internal use:

• _coerceRunEffects, _attachSelectionHandlers, _safeRemove
• _commitHistorySnapshot, _applyHistorySnapshot
• _sanitizePersistentDataForExport, _collectAssemblyComponentUpdates
• #runFeatureEntryMigrations, #linkFeatureParams, #prepareFeatureEntry, #prepareFeatureList
• #disposeSceneObjects, #disposeObjectResources, #disposeMaterialResources

Related helper

extractDefaultValues(schema)

Exported alongside PartHistory. Returns a deep-cloned object of default_value for each schema key.

Usage examples

Basic feature run

import { PartHistory } from './PartHistory.js';

const history = new PartHistory();
const feature = await history.newFeature('Sketch');
// set feature.inputParams as needed
await history.runHistory();

Expressions

history.expressions = "x = 10; y = x * 2;";
feature.inputParams.depth = "y + 5";
await history.runHistory();

Save / load

const json = await history.toJSON();

const restored = new PartHistory();
await restored.fromJSON(json);
await restored.runHistory();

Undo / redo

history.queueHistorySnapshot();
await history.undoFeatureHistory();
await history.redoFeatureHistory();