Package org.tinfour.interpolation

Class TriangularFacetSpecialInterpolator

  • All Implemented Interfaces:
    IProcessUsingTin, IInterpolatorOverTin
    public class TriangularFacetSpecialInterpolator
extends Object
implements IInterpolatorOverTin
    Provides interpolation based on treating the surface as a collection of triangular facets with special handling for regions outside the domain of the Delaunay triangulation.

    • Constructor Detail

      • TriangularFacetSpecialInterpolator

        public TriangularFacetSpecialInterpolator​(IIncrementalTin tin)
        Construct an interpolator that operates on the specified TIN. Because the interpolator will access the TIN on a read-only basis, it is possible to construct multiple instances of this class and allow them to operate in parallel threads.

        This class uses logic similar to the TriangularFacetInterpolator, but clips input coordinates to the domain of the Delaunay triangulation.

        Important Synchronization Issue

        To improve performance, the classes in this package frequently maintain state-data about the TIN that can be reused for query to query. They also avoid run-time overhead by not implementing any kind of Java synchronization or or even the concurrent-modification testing provided by the Java collection classes. If an application modifies the TIN, instances of this class will not be aware of the change. In such cases, interpolation methods may fail by either throwing an exception or, worse, returning an incorrect value. The onus is on the calling application to manage the use of this class and to ensure that no modifications are made to the TIN between interpolation operations. If the TIN is modified, the internal state data for this class must be reset using a call to resetForChangeToTIN().

        Parameters:
        tin - a valid instance of an incremental TIN.

    • Method Detail

      • resetForChangeToTin

        public void resetForChangeToTin()
        Used by an application to reset the state data within the interpolator when the content of the TIN may have changed. Reseting the state data unnecessarily may result in a minor performance reduction when processing a large number of interpolations, but is otherwise harmless.
        Specified by:
        resetForChangeToTin in interface IProcessUsingTin

      • isSurfaceNormalSupported

        public boolean isSurfaceNormalSupported()
        Description copied from interface: IInterpolatorOverTin
        Indicates whether the interpolation class supports the computation of surface normals through the getUnitNormal() method.
        Specified by:
        isSurfaceNormalSupported in interface IInterpolatorOverTin
        Returns:
        true if the class implements the ability to compute surface normals; otherwise, false.

      • getSurfaceNormal

        public double[] getSurfaceNormal()
        Gets the unit normal to the surface at the position of the most recent interpolation. The unit normal is computed based on the partial derivatives of the surface polynomial evaluated at the coordinates of the query point. Note that this method assumes that the vertical and horizontal coordinates of the input sample points are isotropic.
        Specified by:
        getSurfaceNormal in interface IInterpolatorOverTin
        Returns:
        if defined, a valid array of dimension 3 giving the x, y, and z components of the normal, respectively; otherwise, a zero-sized array.

      • getMethod

        public String getMethod()
        Description copied from interface: IInterpolatorOverTin
        Gets a string describing the interpolation method that can be used for labeling graphs and printouts. Because this string may be used as a column header in a table, its length should be kept short.
        Specified by:
        getMethod in interface IInterpolatorOverTin
        Returns:
        A valid string

      • interpolate

        public double interpolate​(double x,
                          double y,
                          IVertexValuator valuator)
        Performs an interpolation with special handling to provide values for regions to the exterior of the Delaunay Triangulation. If the query point (x,y) lies inside the triangulation, the interpolation will is performed using the coordinates of the enclosing triangle. If the query point (x,y) lies to the exterior, it will be projected down to the nearest edge and a value will be interpolated between the values of the edge-defining vertices (v0, v1).

        When the query point is outside the TIN, the normal vector is computed based on the behavior of the plane generated by the z values in the region adjacent to the perimeter edge.

        This method does not perform an extrapolation. Instead, the computed value is assigned the value of the nearest point on the convex hull of the TIN. Consequently, the valid domain for input coordinates covers the full range of finite floating-point values.

        Note that this method can still return a NaN value if the TIN is not populated with at least one non-trivial triangle.

        Specified by:
        interpolate in interface IInterpolatorOverTin
        Parameters:
        x - the planar x coordinate of the interpolation point
        y - the planar y coordinate of the interpolation point
        valuator - a valid valuator for interpreting the z value of each vertex or a null value to use the default.
        Returns:
        if successful, a valid floating point value; otherwise, NaN.