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 * (the "License"); you may not use this file except in compliance with
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package org.apache.commons.math3.analysis.interpolation;

import org.apache.commons.math3.analysis.MultivariateFunction;
import org.apache.commons.math3.exception.DimensionMismatchException;
import org.apache.commons.math3.exception.NoDataException;
import org.apache.commons.math3.exception.NotPositiveException;
import org.apache.commons.math3.exception.NullArgumentException;
import org.apache.commons.math3.random.UnitSphereRandomVectorGenerator;

Interpolator that implements the algorithm described in
William Dudziak's
MS thesis.
Since:
3.6/**
 * Interpolator that implements the algorithm described in
 * <em>William Dudziak</em>'s
 * <a href="http://www.dudziak.com/microsphere.pdf">MS thesis</a>.
 *
 * @since 3.6
 */
public class MicrosphereProjectionInterpolator
    implements MultivariateInterpolator {
    
Brightness exponent. /** Brightness exponent. */
    private final double exponent;
    
Microsphere. /** Microsphere. */
    private final InterpolatingMicrosphere microsphere;
    
Whether to share the sphere. /** Whether to share the sphere. */
    private final boolean sharedSphere;
    
Tolerance value below which no interpolation is necessary. /** Tolerance value below which no interpolation is necessary. */
    private final double noInterpolationTolerance;

    
Create a microsphere interpolator.
Params:
dimension – Space dimension.
elements – Number of surface elements of the microsphere.
exponent – Exponent used in the power law that computes the
maxDarkFraction – Maximum fraction of the facets that can be dark. If the fraction of "non-illuminated" facets is larger, no estimation of the value will be performed, and the background value will be returned instead.
darkThreshold – Value of the illumination below which a facet is
considered dark.
background – Value returned when the maxDarkFraction threshold is exceeded.
sharedSphere – Whether the sphere can be shared among the interpolating function instances. If true, the instances will share the same data, and thus will not be thread-safe.
noInterpolationTolerance – When the distance between an
interpolated point and one of the sample points is less than this
value, no interpolation will be performed (the value of the sample
will be returned).
Throws:
NotStrictlyPositiveException –  if dimension <= 0 or elements <= 0.
NotPositiveException – if exponent < 0.
NotPositiveException – if darkThreshold < 0.
OutOfRangeException – if maxDarkFraction does not belong to the interval [0, 1]./**
     * Create a microsphere interpolator.
     *
     * @param dimension Space dimension.
     * @param elements Number of surface elements of the microsphere.
     * @param exponent Exponent used in the power law that computes the
     * @param maxDarkFraction Maximum fraction of the facets that can be dark.
     * If the fraction of "non-illuminated" facets is larger, no estimation
     * of the value will be performed, and the {@code background} value will
     * be returned instead.
     * @param darkThreshold Value of the illumination below which a facet is
     * considered dark.
     * @param background Value returned when the {@code maxDarkFraction}
     * threshold is exceeded.
     * @param sharedSphere Whether the sphere can be shared among the
     * interpolating function instances.  If {@code true}, the instances
     * will share the same data, and thus will <em>not</em> be thread-safe.
     * @param noInterpolationTolerance When the distance between an
     * interpolated point and one of the sample points is less than this
     * value, no interpolation will be performed (the value of the sample
     * will be returned).
     * @throws org.apache.commons.math3.exception.NotStrictlyPositiveException
     * if {@code dimension <= 0} or {@code elements <= 0}.
     * @throws NotPositiveException if {@code exponent < 0}.
     * @throws NotPositiveException if {@code darkThreshold < 0}.
     * @throws org.apache.commons.math3.exception.OutOfRangeException if
     * {@code maxDarkFraction} does not belong to the interval {@code [0, 1]}.
     */
    public MicrosphereProjectionInterpolator(int dimension,
                                             int elements,
                                             double maxDarkFraction,
                                             double darkThreshold,
                                             double background,
                                             double exponent,
                                             boolean sharedSphere,
                                             double noInterpolationTolerance) {
        this(new InterpolatingMicrosphere(dimension,
                                          elements,
                                          maxDarkFraction,
                                          darkThreshold,
                                          background,
                                          new UnitSphereRandomVectorGenerator(dimension)),
             exponent,
             sharedSphere,
             noInterpolationTolerance);
    }

    
Create a microsphere interpolator.
Params:
microsphere – Microsphere.
exponent – Exponent used in the power law that computes the
weights (distance dimming factor) of the sample data.
sharedSphere – Whether the sphere can be shared among the interpolating function instances. If true, the instances will share the same data, and thus will not be thread-safe.
noInterpolationTolerance – When the distance between an
interpolated point and one of the sample points is less than this
value, no interpolation will be performed (the value of the sample
will be returned).
Throws:
NotPositiveException – if exponent < 0./**
     * Create a microsphere interpolator.
     *
     * @param microsphere Microsphere.
     * @param exponent Exponent used in the power law that computes the
     * weights (distance dimming factor) of the sample data.
     * @param sharedSphere Whether the sphere can be shared among the
     * interpolating function instances.  If {@code true}, the instances
     * will share the same data, and thus will <em>not</em> be thread-safe.
     * @param noInterpolationTolerance When the distance between an
     * interpolated point and one of the sample points is less than this
     * value, no interpolation will be performed (the value of the sample
     * will be returned).
     * @throws NotPositiveException if {@code exponent < 0}.
     */
    public MicrosphereProjectionInterpolator(InterpolatingMicrosphere microsphere,
                                             double exponent,
                                             boolean sharedSphere,
                                             double noInterpolationTolerance)
        throws NotPositiveException {
        if (exponent < 0) {
            throw new NotPositiveException(exponent);
        }

        this.microsphere = microsphere;
        this.exponent = exponent;
        this.sharedSphere = sharedSphere;
        this.noInterpolationTolerance = noInterpolationTolerance;
    }

    
{@inheritDoc}
Throws:
DimensionMismatchException – if the space dimension of the
given samples does not match the space dimension of the microsphere./**
     * {@inheritDoc}
     *
     * @throws DimensionMismatchException if the space dimension of the
     * given samples does not match the space dimension of the microsphere.
     */
    public MultivariateFunction interpolate(final double[][] xval,
                                            final double[] yval)
        throws DimensionMismatchException,
               NoDataException,
               NullArgumentException {
        if (xval == null ||
            yval == null) {
            throw new NullArgumentException();
        }
        if (xval.length == 0) {
            throw new NoDataException();
        }
        if (xval.length != yval.length) {
            throw new DimensionMismatchException(xval.length, yval.length);
        }
        if (xval[0] == null) {
            throw new NullArgumentException();
        }
        final int dimension = microsphere.getDimension();
        if (dimension != xval[0].length) {
            throw new DimensionMismatchException(xval[0].length, dimension);
        }

        // Microsphere copy.
        final InterpolatingMicrosphere m = sharedSphere ? microsphere : microsphere.copy();

        return new MultivariateFunction() {
            
{inheritDoc} /** {inheritDoc} */
            public double value(double[] point) {
                return m.value(point,
                               xval,
                               yval,
                               exponent,
                               noInterpolationTolerance);
            }
        };
    }
}