/**
* Java Modular Image Synthesis Toolkit (JMIST)
* Copyright (C) 2008-2013 Bradley W. Kimmel
*
* Permission is hereby granted, free of charge, to any person
* obtaining a copy of this software and associated documentation
* files (the "Software"), to deal in the Software without
* restriction, including without limitation the rights to use,
* copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following
* conditions:
*
* The above copyright notice and this permission notice shall be
* included in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
* OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
* HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
* WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
* OTHER DEALINGS IN THE SOFTWARE.
*/
package ca.eandb.jmist.framework.scatter;
import ca.eandb.jmist.framework.Function1;
import ca.eandb.jmist.framework.Random;
import ca.eandb.jmist.framework.SurfacePointGeometry;
import ca.eandb.jmist.framework.function.ConstantFunction1;
import ca.eandb.jmist.framework.random.RandomUtil;
import ca.eandb.jmist.math.Optics;
import ca.eandb.jmist.math.Vector3;
/**
* A <code>SurfaceScatterer</code> representing the interface between two
* dielectric media.
* @author Brad Kimmel
*/
public final class FresnelSurfaceScatterer implements SurfaceScatterer {
/** Serialization version ID. */
private static final long serialVersionUID = 3330860331562235908L;
/** The refractive index of the medium above the interface. */
private final Function1 riBelow;
/** The refractive index of the medium below the interface. */
private final Function1 riAbove;
/**
* Creates a new <code>FresnelSurfaceScatterer</code>.
* @param riBelow The refractive index of the medium below the interface.
* @param riAbove The refractive index of the medium above the interface.
*/
public FresnelSurfaceScatterer(Function1 riBelow, Function1 riAbove) {
this.riBelow = riBelow;
this.riAbove = riAbove;
}
/**
* Creates a new <code>FresnelSurfaceScatterer</code>.
* @param riBelow The refractive index of the medium below the interface.
* @param riAbove The refractive index of the medium above the interface.
*/
public FresnelSurfaceScatterer(double riBelow, double riAbove) {
this(new ConstantFunction1(riBelow), new ConstantFunction1(riAbove));
}
/* (non-Javadoc)
* @see ca.eandb.jmist.framework.scatter.SurfaceScatterer#scatter(ca.eandb.jmist.framework.SurfacePointGeometry, ca.eandb.jmist.math.Vector3, boolean, ca.eandb.jmist.framework.color.WavelengthPacket, ca.eandb.jmist.framework.Random)
*/
public Vector3 scatter(SurfacePointGeometry x, Vector3 v, boolean adjoint,
double lambda, Random rnd) {
double n1 = riAbove.evaluate(lambda);
double n2 = riBelow.evaluate(lambda);
Vector3 N = x.getNormal();
double R = Optics.reflectance(v, n1, n2, N);
if (RandomUtil.bernoulli(R, rnd)) {
return Optics.reflect(v, N);
} else {
return Optics.refract(v, n1, n2, N);
}
}
}