Spline Nodes

Spline nodes work with Unity Spline data. Some nodes sample a Spline into Point data (Spline Sampler), while others build a Spline from Point data (Create Spline from Points). All nodes in this category use the purple node color (#B34DB3).

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Spline Sampler

Category: Spline
Description: Samples points along or inside splines and outputs Point data with spline-derived attributes.

The node can operate in two dimensions:

• OnSpline — samples positions along the spline curve itself.
• OnInterior — fills the enclosed area of a closed spline with a regular grid of points (XZ-plane projected).

Ports

Direction	Name	Type
Input	Spline	Spline
Output	Out	Point

Settings

Dimension

Field	Type	Default	Description
dimension	SplineSamplerDimension	OnSpline	Whether to place points along the spline curve or fill the closed interior.

SplineSamplerDimension enum

Value	Description
OnSpline	Samples positions directly on the spline curve at regular count or distance intervals.
OnInterior	Grid-scans the XZ bounding box of a closed spline and keeps only points inside the polygon. Requires a closed spline.

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On Spline

Field	Type	Default	Description
mode	SampleMode	ByCount	How sample positions are determined. See SampleMode enum below.
sampleCount	int	20	Number of evenly-spaced samples. Used when mode = ByCount. Minimum is 2.
sampleDistance	float	1.0	World-space distance between samples. Used when mode = ByDistance. Minimum is 0.001.
includeEndPoints	bool	true	When mode = ByDistance, guarantees the spline end point (t = 1) is always included.

SampleMode enum

Value	Description
ByCount	Divides the normalised spline parameter [0, 1] into sampleCount - 1 equal steps.
ByDistance	Steps along the spline in world-space increments of sampleDistance.

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On Interior

Field	Type	Default	Description
interiorSpacing	float	1.0	XZ grid cell spacing in world units. Smaller values create denser point clouds. Minimum is 0.01.
densityFalloff	bool	false	When enabled, reduces point density near the spline boundary using a linear falloff.
falloffDistance	float	2.0	World-space distance from the boundary over which density falls to zero. Only effective when densityFalloff is enabled.

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Spline Filtering

Field	Type	Default	Description
useAllSplines	bool	true	Process all splines in the input SplineContainer. Disable to filter by index.
splineMask	int	~0	Bitmask controlling which spline indices are processed when useAllSplines is false. Each bit corresponds to one spline index (bit 0 = spline 0, etc.). Hidden in the inspector.

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Attributes

Field	Type	Default	Description
outputCurvature	bool	true	Compute and store spline curvature at each sample point as the SplineCurvature attribute.

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Provided Attributes

The following metadata attributes are always written to every output point:

Attribute Name	Type	Description
SplineAlpha	float	Normalised spline parameter t in the range [0, 1]. 0 = spline start, 1 = spline end.
SplineDistance	float	World-space arc-length distance from the spline start, in units. Computed as t × splineLength.
SplineCurvature	float	Curvature magnitude at the sample point. Only written when outputCurvature is enabled.
SplineBorderDistance	float	Minimum world-space distance from the point to the spline boundary polygon. OnInterior only.

All four are declared through IPPGAttributeProvider.

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Point Transform

Every sampled point receives:

• Position: The spline position converted from world space into the PPGComponent's local space.
• Rotation: A look-rotation built from the spline tangent and up vectors at the sample position. Interior points use the tangent/up of the nearest spline boundary point.
• Scale: (1, 1, 1) (unit scale).
• Density: 1.0 for OnSpline points. For OnInterior points, 1.0 unless densityFalloff is enabled, in which case the value linearly decays to 0 within falloffDistance of the boundary.

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Tips

• The interior polygon is approximated with 64 line segments; highly irregular splines may produce minor sampling artefacts near concave regions.
• Curvature is computed using finite differences (h = 0.001) on the spline parameter. Very short splines or near-zero tangents may produce 0.
• Each spline in the input container produces a separate PPGPointData output batch. Downstream filter nodes see each batch independently.
• OnInterior requires a closed spline. If the spline is open, a warning is logged and the spline is skipped.
• To sample only specific splines from a multi-spline SplineContainer, disable useAllSplines and set the splineMask bitmask via script or a custom editor.

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Create Spline from Points

Category: Spline Description: Constructs a world-space Spline from an ordered list of Point data. Bridges the Point world (samplers, procedural point sources, point-op nodes) back into the Spline world so the result can feed Spline Mesh Deformer, Spline Sampler, Filter By Spline, or any other Spline-consuming node.

The canonical use case is terrain conforming splines: sample an authored spline, project the sampled points onto a terrain via Project To Surface, then reconstruct a spline that follows the terrain surface.

Ports

Direction	Name	Type
Input	In	Point
Output	Out	Spline

Settings

Field	Type	Default	Description
tangentMode	SplineTangentMode	Auto	Tangent mode applied to all knots of the output spline.
closed	bool	false	Create a closed loop spline.
sortByAttribute	bool	false	Sort input points by a float attribute before using them as knots. Useful when upstream nodes (filters, sorters) have disturbed the original order.
sortAttributeName	string	"SplineAlpha"	Attribute name used for sorting when sortByAttribute is enabled. SplineAlpha is produced by Spline Sampler, so the default works for the common Sampler → ... → CreateSpline flow.
useKnotRotation	bool	true	Use each point's rotation as the knot rotation. Disable to fall back to quaternion.identity.

SplineTangentMode enum

Value	Description
Auto	Alias for AutoSmooth. Tangents are computed automatically for smooth curves through the knots.
Linear	Straight-line segments between knots. Each knot becomes a sharp corner.
AutoSmooth	Same as Auto; listed explicitly for clarity.

Behavior

1. Each input PPGPointData becomes one output PPGSplineData (1:1 per-group mapping, matching Spline Sampler's output pattern).
2. Input points must be in component-local space; the node converts each to world space via the component's transform (consistent with every other spline producer in the package).
3. Knot positions, tangents (left as zero — AutoSmooth / Linear compute them automatically), and rotations are written; the spline is then fed back through the graph as world-space data.
4. Groups with fewer than two usable knots are skipped with a warning. When sortByAttribute is on but the attribute is missing, the node falls back to array order with a single warning.

Example: Terrain-conforming Road

Get Binding (SplineContainer)
  └─▶ Spline Sampler (ByCount = 16)
        └─▶ Project To Surface (Terrain)
              └─▶ Create Spline from Points
                    └─▶ Spline Mesh Deformer

The road mesh from the Deformer follows the terrain surface because the driving spline's knots were projected onto it.

Tips

• Input point count is the output spline's knot count. For smooth curves, 12–32 knots are typically enough; more does not always help because AutoSmooth adds curvature between knots.
• If a filter or sort node reorders points between Spline Sampler and Create Spline from Points, enable sortByAttribute with SplineAlpha so the original spline traversal order is restored before knot construction.
• For procedural point sources (Poisson Disk, Grid, Manual Placement) that lack SplineAlpha, leave sortByAttribute disabled — the array order is used directly.