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/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
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
* <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. */
private final double exponent;
/** Microsphere. */
private final InterpolatingMicrosphere microsphere;
/** Whether to share the sphere. */
private final boolean sharedSphere;
/** Tolerance value below which no interpolation is necessary. */
private final double noInterpolationTolerance;
/**
* 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.
*
* @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.
*/
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} */
public double value(double[] point) {
return m.value(point,
xval,
yval,
exponent,
noInterpolationTolerance);
}
};
}
}
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