Class AcGeNurbsCurve

A NURBS curve implementation that can be used by other curve classes

Constructors

constructor

Methods

clone controlPoints degree evaluate getOffsetSamplePath2d getParameterRange getPoints isClosed knots length nearestPoint point signedPlanarCurvatureAt weights byKnotsControlPointsWeights byPoints createClosedCurve createFitPointsForClosedCurve

Constructors

constructor

  • new AcGeNurbsCurve(
        degree: number,
        knots: number[],
        controlPoints: AcGeVector3dLike[],
        weights?: number[],
    ): AcGeNurbsCurve

  • Creates a NURBS curve from degree, knots, control points, and optional weights.

    When weights is omitted, all control points receive a weight of 1.0 (non-rational B-spline).

    Parameters

    • degree: number

      Polynomial degree p of the basis functions

    • knots: number[]

      Non-decreasing knot vector of length n + p + 1

    • controlPoints: AcGeVector3dLike[]

      Control points in curve order

    • Optionalweights: number[]

      Optional rational weights aligned with control points

    Returns AcGeNurbsCurve

Methods

clone

  • clone(): AcGeNurbsCurve

  • Return a deep-cloned copy of this NURBS curve.

    Returns AcGeNurbsCurve

controlPoints

degree

  • degree(): number

  • Get the degree of the NURBS curve

    Returns number

evaluate

  • evaluate(u: number): AcGeNurbsEvaluation

  • Evaluates position and parametric derivatives at parameter u.

    Returns the rational NURBS point together with first- and second-order parametric derivatives computed analytically from the basis functions.

    Parameters

    • u: number

      Curve parameter in the valid knot span

    Returns AcGeNurbsEvaluation

    Position point, first derivative deriv1, and second derivative deriv2

getOffsetSamplePath2d

  • getOffsetSamplePath2d(
        offsetDist: number,
        maxSamples?: number,
    ): { points: AcGePoint2d[]; tangents: AcGePoint2d[] }

  • Samples a 2D path with analytic tangents for planar offset.

    Builds an initial uniform parameter list scaled by curve length and offset distance, then refines intervals where |offsetDist| * |curvature| exceeds 0.85 (potential cusp region). Each final sample includes a unit tangent derived from the analytic first derivative.

    Parameters

    • offsetDist: number

      Signed offset distance used to choose sample density

    • OptionalmaxSamples: number

      Upper bound on the number of returned samples (default 512)

    Returns { points: AcGePoint2d[]; tangents: AcGePoint2d[] }

    XY samples and matching unit tangents in parameter order

getParameterRange

  • getParameterRange(): { end: number; start: number }

  • Get the valid parameter range for this curve

    Returns { end: number; start: number }

getPoints

  • getPoints(divisions: number): number[][]

  • Get points along the curve

    Parameters

    • divisions: number

      Number of divisions to create

    Returns number[][]

    Array of points along the curve

isClosed

  • isClosed(tolerance?: number): boolean

  • Check if the curve is closed by comparing start and end points

    Parameters

    • Optionaltolerance: number

    Returns boolean

knots

  • knots(): number[]

  • Get the knot vector

    Returns number[]

length

  • length(): number

  • Calculate curve length using numerical integration

    Returns number

nearestPoint

  • nearestPoint(point: AcGeVector3dLike, samples?: number): AcGeVector3dLike

  • Returns the nearest point on this NURBS curve to the given point.

    Evaluates the curve at uniform steps in parameter space over the valid knot span.

    Parameters

    • point: AcGeVector3dLike

      Query point.

    • Optionalsamples: number

      Number of interior samples (default 64).

    Returns AcGeVector3dLike

point

  • point(u: number): number[]

  • Calculates a point on the curve at parameter u.

    Delegates to evaluate and returns only the position component.

    Parameters

    • u: number

      Curve parameter in the valid knot span

    Returns number[]

    Evaluated point as [x, y, z]

signedPlanarCurvatureAt

  • signedPlanarCurvatureAt(u: number): number

  • Signed curvature in the XY plane at parameter u.

    Uses the standard planar formula (x'y'' - y'x'') / (x'^2 + y'^2)^(3/2) applied to the parametric derivatives from evaluate.

    Parameters

    • u: number

      Curve parameter in the valid knot span

    Returns number

    Signed curvature; positive indicates counterclockwise bending

weights

  • weights(): number[]

  • Get the weights

    Returns number[]

StaticbyKnotsControlPointsWeights

  • byKnotsControlPointsWeights(
        degree: number,
        knots: number[],
        controlPoints: AcGeVector3dLike[],
        weights?: number[],
    ): AcGeNurbsCurve

  • Create a NURBS curve from control points and knots

    Parameters

    • degree: number
    • knots: number[]
    • controlPoints: AcGeVector3dLike[]
    • Optionalweights: number[]

    Returns AcGeNurbsCurve

StaticbyPoints

  • byPoints(
        points: number[][],
        degree: number,
        parameterization?: AcGeKnotParameterizationType,
        startTangent?: number[],
        endTangent?: number[],
    ): AcGeNurbsCurve

  • Create a NURBS curve from fit points using interpolation

    Parameters

    • points: number[][]
    • degree: number
    • Optionalparameterization: AcGeKnotParameterizationType
    • OptionalstartTangent: number[]
    • OptionalendTangent: number[]

    Returns AcGeNurbsCurve

StaticcreateClosedCurve

StaticcreateFitPointsForClosedCurve

  • createFitPointsForClosedCurve(points: AcGeVector3dLike[]): AcGePoint3d[]

  • Create fit points for a closed NURBS curve using Catmull-Rom interpolation

    Parameters

    Returns AcGePoint3d[]

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