`TrailSplineSource`

← prev index next →

Draws the rolling trail left behind a moving node — the way to render a wake, comet tail, or motion streak that follows an object and fades out over the last N positions it visited.

Declarative element: <sk-trail-spline-source>

Global: available as sk.TrailSplineSource inside a scene <script>.

Remarks

This is the motion-driven member of the spline-source family: a spline-source supplies the curve geometry for a AbstractSpline, so it lives as the single geometry child of a sk-spline. Unlike the static sources, its curve is not authored — it is fed one new head position at a time. Each head position beyond a small distance threshold is prepended to a fixed-capacity ring buffer (oldest trimmed at the far end), and the buffer is re-evaluated as a Catmull-Rom curve, so the spline is a smooth polyline through the object's recent path. Every vertex has width 1.0; taper the trail with the host spline's width profile.

Key attributes. max-points is the trail length — the ring-buffer capacity (minimum 2); a larger value keeps a longer tail. head-pos is the current head position in world space and is what actually grows the trail: it is animatable, but the usual wiring is a child sk-follow-constraint mapping a moving node's pos onto this source's head-pos, so the trail tracks that node automatically. Like every spline-source it also carries the family's distribution / distribution-count controls: a spline-source is itself a points-source, so a sk-cloner given one places clones along the trail curve, and these controls choose how it is sampled into those positions.

Related. It is one input modality of the spline-source family alongside sk-svg-spline-source, sk-points-spline-source, sk-morph-spline-source, and the GPU sources sk-compute-buffer-spline-source / sk-custom-wgsl-spline-source. It is typically driven by a sk-follow-constraint; its host is a sk-spline, whose curve then draws with a stroke paint or carries an sk-align-to-spline-constraint.

Constructor

constructor(config?: { maxPoints: number })

Inherited from: SkenraAnimatable — see those pages for inherited members.

Properties

Config Properties

Property	Type	Default	Description	Declared by
`maxPoints`	`number`	—	Maximum number of control points in the trail (minimum 2).	`TrailSplineSource`

Other Properties

Property	Type	Default	Description	Declared by
`pointCount`read-only	`number`	—	Cloner-facing point count. Tracks `distribution`: equals	`TrailSplineSource`
`localMatrices`read-only	`Float32Array<ArrayBufferLike> \| null`	—	Per-vertex `[ T·width \| N·width \| B·width \| P ]` frame matrices, or `null` until data is available.	`TrailSplineSource`
`distribution`	`SplineDistributionMode`	—	How clone points are placed along the trail — at the control points, at	`TrailSplineSource`
`distributionCount`	`number`	—	The number of evenly spaced points to place when the distribution is	`TrailSplineSource`
`headPos`animatable	`Point3D`	`[0, 0, 0]`	The head position of the trail (world space).	`TrailSplineSource`
`controlPointCount`read-only	`number`	—	The number of control points currently in the buffer.	`TrailSplineSource`
`vertexCount`read-only	`number`	—	Number of vertices in the linearized polyline.	`TrailSplineSource`
`isValid`read-only	`boolean`	—	Whether the source initialized successfully and holds at least one vertex.	`TrailSplineSource`
`isClosed`read-only	`boolean`	`false`	Whether the spline forms a closed loop (last vertex joins the first).	`TrailSplineSource`
`polyline`read-only	`readonly Readonly<SplinePoint>[]`	`[]`	Read-only view of the internal 3D polyline points.	`TrailSplineSource`
`scene`read-only	`any`	—	Gets the Scene this animatable belongs to, if any.	`SkenraAnimatable`
`animations`read-only	`SkenraAnimation[]`	—	Public getter for the animations affecting this target.	`SkenraAnimatable`

Methods

Method	Description	Declared by
`pointAt(t: number): SplinePoint \| null`	Point on the trail at normalized arc-length position `t` in [0, 1], or `null` if empty.	`TrailSplineSource`
`getBoundsInSpace(fullTransform: Float32Array): PolylineBounds \| null`	Axis-aligned bounding box of the produced points, expressed in the given target space, or `null` if there is no data yet.	`TrailSplineSource`
`animate(firstArg: TypedKeyframe<this>[] \| TypedPropertyIndexedKeyframes<this> \| Record<string, any> \| globalThis.Keyframe[] \| globalThis.PropertyIndexedKeyframes \| null, secondArg?: number \| KeyframeAnimationOptions \| globalThis.KeyframeAnimationOptions): SkenraAnimation & Animation`	Creates a new SkenraAnimation for this target per Web Animations API.	`SkenraAnimatable`
`removeAnimation(animation: SkenraAnimation): boolean`	Removes a specific animation from this object.	`SkenraAnimatable`
`constrain(type: K, config: ConstraintConfigMap[K]): ConstraintReturnMap[K]`	Creates a constraint on this Animatable using a fluent API.	`SkenraAnimatable`

Example

const trailSource = new TrailSplineSource({ maxPoints: 64 });
const trailSpline = new Spline({ id: 'trail', source: trailSource });

// Link to a moving object
trailSource.constrain('follow', {
    source: sphere,
    mappings: [{ source: 'pos', target: 'headPos' }],
});

↑ Documentation home · ← All classes