Layer

Abstract base class for any layer that can be added to a viewport.

A layer owns a set of renderable objects and contributes them to the scene each frame. Subclasses such as ImageLayer, VolumeLayer, and LabelLayer implement update to build or refresh those objects for the current view. Custom layers register objects with addObject and report readiness through setState.

Layers carry shared presentation state in opacity, blendMode, and occludes, and expose a lifecycle LayerState that observers can subscribe to. A layer instance may be attached to only one viewport at a time.

class Particles extends Layer {
  public readonly type = "Particles";

  constructor(points: PointProps[]) {
    super();
    this.addObject(new PointsRenderable(points));
    this.setState("ready");
  }

  public update() {}
}

viewport.addLayer(new Particles(points));

Extended by

• AxesLayer
• ImageLayer
• VolumeLayer
• LabelLayer

Constructor

Creates a layer with the given presentation state.

new Layer(props?): Layer;

Parameter	Description
props: LayerProps	Initialization properties. Defaults to {}.

Types

ChannelProps

Appearance settings for a single image channel.

Property	Description
visible?: boolean	Whether the channel is drawn. Defaults to true.
color?: ColorLike	The channel's tint color. Defaults to white.
contrastLimits?: [number, number]	Intensity range shown. Defaults to the data range.
opacity?: number	Channel opacity in [0, 1]. Defaults to 1.

LayerState

The loading lifecycle state of a layer.

type LayerState = "initialized" | "loading" | "ready";

BlendMode

How a layer's output blends with previously drawn content.

type BlendMode = 
  | "none"
  | "normal"
  | "additive"
  | "subtractive"
  | "multiply"
  | "premultipliedOver";

StateChangeCallback

A callback invoked after a layer's state changes.

type StateChangeCallback = (newState, prevState?) => void;

LayerProps

Initialization properties for constructing a layer.

Property	Description
opacity?: number	Layer opacity in [0, 1]. Defaults to 1.
blendMode?: BlendMode	How the layer blends. Defaults to "none".
occludes?: boolean	Hides content behind. Inferred from blendMode.

SliceCoordinates

World-space coordinates selecting the data to display.

Property	Description
x?: number	Position on the x axis in world units.
y?: number	Position on the y axis in world units.
z?: number	Position on the z axis in world units.
c?: number[]	Channel indices to load. Defaults to all channels.
t?: number	The time point to display.

PointPickingResult

The result of picking a value from a layer with a click.

Property	Description
world: vec3	The picked position in world units.
value: number	The data value sampled at the position.

SliceOrientation

The plane a 2D slice lies on, named by its in-plane axes.

type SliceOrientation = "XY" | "XZ" | "YZ";

Properties

type

A string identifying the concrete layer type.

abstract readonly type: string;

blendMode

How the layer's output blends with previously drawn content. Also applies to blending between objects within the layer.

blendMode: BlendMode;

occludes

Whether the layer writes depth and hides content drawn behind it.

Occluding layers render a depth pass and always draw before non-occluding layers regardless of their order in the viewport. When not set explicitly this value is inferred from blendMode at construction only. Reassigning blendMode later does not update it.

occludes: boolean;

requiresSceneDepth_

Set to true by subclasses whose shaders read scene depth.

protected requiresSceneDepth_: boolean = false;

Accessors

requiresSceneDepth boolean

Whether the layer's shaders read scene depth. When true the renderer draws occluding layers to a depth texture the layer's shaders can sample. A layer cannot both occlude and read scene depth.

get requiresSceneDepth(): boolean;

opacity number

The layer's opacity in [0, 1]. Values outside are clamped.

get opacity(): number;

set opacity(value): void;

Parameter	Description
value: number	The new opacity in [0, 1].

coverageGroups ReadonlyMap<number | null, readonly RenderableObject[]>

The layer's renderable objects grouped by coverage group. Objects in a group draw each pixel at most once, letting chunks at multiple levels of detail overlap correctly.

get coverageGroups(): ReadonlyMap<number | null, readonly RenderableObject[]>;

state LayerState

The layer's current lifecycle state.

get state(): LayerState;

Methods

update() void

Builds or refreshes the layer's renderable objects for the current view. Called automatically once per frame for every layer in a viewport.

abstract update(viewport?): void;

Parameter	Description
viewport?: Viewport	The viewport being rendered.

onEvent() void

Handles a pointer or wheel event from the owning viewport. Called automatically for each event before the camera controls. The default implementation does nothing.

onEvent(_event): void;

Parameter	Description
_event: EventContext	The event with clip and world coordinates attached.

onAttached() void

Lifecycle hook that is called automatically when a layer is is attached to a viewport. A layer can only be attached to one viewport at a time.

onAttached(context): void;

Parameter	Description
context: IdetikContext	The shared runtime context.

onDetached() void

Lifecycle hook that is called automatically when a layer is detached from a viewport.

onDetached(context): void;

Parameter	Description
context: IdetikContext	The shared runtime context.

addStateChangeCallback() void

Registers a callback invoked after every state change.

addStateChangeCallback(callback): void;

Parameter	Description
callback: StateChangeCallback	Receives the new and previous states.

removeStateChangeCallback() void

Removes a previously registered state change callback.

removeStateChangeCallback(callback): void;

Parameter	Description
callback: StateChangeCallback	The callback to remove.

setState() void

Sets the lifecycle state and notifies state change callbacks.

protected setState(newState): void;

Parameter	Description
newState: LayerState	The state to enter.

addObject() void

Registers a renderable object for drawing. Objects in the same coverage group draw each pixel at most once.

protected addObject(object, coverageGroup?): void;

Parameter	Description
object: RenderableObject	The object to add.
coverageGroup: number | null	The group key. Defaults to null.

clearObjects() void

Removes all registered renderable objects.

protected clearObjects(): void;

getUniforms() Record<string, unknown>

Returns uniform name-value pairs applied to every object drawn by this layer. Override in subclasses that need custom shader uniforms.

getUniforms(): Record<string, unknown>;