VTK WebAssembly JavaScript

The vtkWebAssembly.mjs module provides JavaScript bindings to VTK WebAssembly using Emscripten. It includes two key classes:

• vtkStandaloneSession: For standalone VTK WebAssembly apps capable of creating and manipulating VTK objects.

• vtkRemoteSession: For remote VTK WebAssembly apps meant to sync with a VTK application on a remote server.

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Global Functions

Function	Description
getVTKVersion()	Returns the short VTK version string (e.g., "9.4.2" or "9.4.20250508).
getVTKVersionFull()	Returns the full VTK version string (e.g., "9.4.2-2017-gd453d24731").

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vtkStandaloneSession

Provides methods to directly create, manage, and manipulate VTK objects.

Constructor

new vtkStandaloneSession()

Methods

Signature	Description
create(className: string) => number	Creates a new VTK object.
destroy(objectId: number) => boolean	Destroys a previously created VTK object.
set(objectId: number, properties: object) => undefined	Apply properties from JSON object to the VTK object.
get(objectId: number) => object	Retrieves the state of the given object.
invoke(objectId: number, methodName: string, args: object) => object	Invokes a method on the object with JSON arguments.
observe(objectId: number, eventName: string, callback: Function) => number	Registers a JavaScript callback for a VTK event.
unObserve(objectId: number, tag: number) => boolean	Unregisters an observer using its tag.

vtkRemoteSession

Wraps around VTK session C API for client-server WebAssembly rendering. This is more suitable when the rendering state is controlled remotely.

Constructor

new vtkRemoteSession()

Methods

Signature	Description
registerState(state: object) => boolean	Registers a VTK object state.
unRegisterState(objectId: number) => boolean	Unregisters an object’s state.
getState(objectId: number) => object	[Deprecated] Retrieves the object’s current state.
set(objectId: number, properties: object) => undefined	Apply properties from JSON object to the VTK object.
get(objectId: number) => object	Retrieves the state of the given object.
skipProperty(className: string, propertyName: string) => void	Prevents a property from being (de)serialized.
unSkipProperty(className: string, propertyName: string) => void	Re-enables serialization for a property.
registerBlob(hash: string, jsArray: Uint8Array) => boolean	Registers a binary blob.
unRegisterBlob(hash: string) => boolean	Unregisters a blob using its hash.
getBlob(hash: string) => Uint8Array	Retrieves a registered blob.
invoke(objectId: number, methodName: string, args: object) => object	Calls a method on a VTK object.
getAllDependencies(objectId: number) => Uint32Array	Returns object dependency handles.
updateObjectFromState(state: object) => void	Applies a JSON state to an object.
updateStateFromObject(objectId: number) => void	Updates the state JSON from the object.
setSize(objectId: number, width: number, height: number) => boolean	Sets the size of a render window.
render(objectId: number) => boolean	Triggers a render operation.
resetCamera(objectId: number) => boolean	Resets the camera for the given scene.
startEventLoop(objectId: number) => boolean	Begins the VTK interactor event loop.
stopEventLoop(objectId: number) => boolean	Stops the VTK interactor event loop.
bindRenderWindow(objectId: number, canvasSelector: string) => boolean	Binds a VTK render window to an HTML canvas element.
observe(objectId: number, eventName: string, callback: Function) => number	Observes events on an object.
unObserve(objectId: number, tag: number) => boolean	Removes an observer by tag.
export(fileName: string) => void	Exports the state and blobs.
import(stateFile: string, blobFile: string) => void	Imports a scene and associated data.
updateObjectsFromStates() => void	Applies all registered states to their respective objects.
updateStatesFromObjects() => void	Refreshes all states based on their current object data.
pruneUnusedBlobs() => void	Deletes unused blobs.
pruneUnusedObjects() => void	Deletes unused objects.
pruneUnusedStates() => void	Deletes unused states.
clear() => void	Clears all objects, blobs, and state.
getTotalBlobMemoryUsage() => number	Returns memory usage of all blobs.
getTotalVTKDataObjectMemoryUsage() => number	Returns memory usage of all VTK data objects.
printSceneManagerInformation() => void	Prints internal scene manager details.
setDeserializerLogVerbosity(level: string) => void	Sets verbosity for deserialization.
setInvokerLogVerbosity(level: string) => void	Sets verbosity for method invocations.
setObjectManagerLogVerbosity(level: string) => void	Sets verbosity for the object manager.
setSerializerLogVerbosity(level: string) => void	Sets verbosity for serialization.

Notes

• All objectId are an unsigned integer.

• All states must be passed as JSON and will be returned as JSON. Do not pass stringified JSON.

• Blob support is useful for caching binary data such as images or meshes to ease network traffic in the remote session use case.