GridBoundaryCondition Structure

public readonly struct GridBoundaryCondition

Public Structure GridBoundaryCondition

public value class GridBoundaryCondition

[<SealedAttribute>]
type GridBoundaryCondition = 
    struct
        inherit ValueType
    end

Inheritance

Object  →  ValueType  →  GridBoundaryCondition

Boundary conditions control how tensor-product grid surfaces access grid values when building local interpolation stencils that extend beyond the grid extent. For example, a 4-point cubic kernel near the grid edge may require samples at indices i=-1 or i=N (outside the valid range [0, N-1]). The boundary condition determines how these out-of-range indices are mapped to valid values.

Distinction from ExtrapolationMode:

• GridBoundaryCondition (this type): Applies during construction/evaluation when the interpolation kernel needs to access grid values outside the nominal index range [0, N-1]. It affects how the stencil is assembled.
• ExtrapolationMode: Applies during query evaluation when a query coordinate falls outside the grid domain. It controls whether to throw an exception, return a fill value, clamp to boundaries, or use periodic/reflective coordinate mapping.

Usage: Boundary conditions are primarily used by tensor-product spline interpolation (via CreateCubicTensorSpline(IReadOnlyList<IReadOnlyList<Double>>, IReadOnlyList<Double>, GridBoundaryCondition, ExtrapolationMode) and CreateTensorSpline(IReadOnlyList<IReadOnlyList<Double>>, IReadOnlyList<Double>, ISplineKernel1D, GridBoundaryCondition, ExtrapolationMode)). The specialized 2D/3D cubic surfaces (created with [!:GridSurface.CreateCubic(Vector<double>, Vector<double>, Matrix<double>)]) do not use GridBoundaryCondition; their boundary behavior is determined by the CubicSplineKind used internally (always Natural in current implementation).

Available boundary conditions:

• Clamp (default): Clamp out-of-range indices to the nearest edge (repeat edge values).
• Periodic: Wrap indices periodically using modulo arithmetic (for periodic data such as angles).
• Reflect: Mirror indices at boundaries for symmetric extension (useful for even functions).
• Fill(Double): Use a constant fill value for out-of-range samples (isolates edges).

Reference