/**
* 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.Basis3;
import ca.eandb.jmist.math.Optics;
import ca.eandb.jmist.math.SphericalCoordinates;
import ca.eandb.jmist.math.Vector3;
/**
* @author bwkimmel
*
*/
public final class TrowbridgeReitzSurfaceScatterer implements SurfaceScatterer {
private final double oblateness;
private final Function1 riBelow;
private final Function1 riAbove;
/**
* @param riBelow
* @param riAbove
*/
public TrowbridgeReitzSurfaceScatterer(double oblateness, Function1 riBelow, Function1 riAbove) {
this.oblateness = oblateness;
this.riBelow = riBelow;
this.riAbove = riAbove;
}
public TrowbridgeReitzSurfaceScatterer(double oblateness, double riBelow, double riAbove) {
this(oblateness, 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, double, 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)) {
Basis3 basis = x.getBasis();
double sigma2 = oblateness * oblateness;
double sigma4 = sigma2 * sigma2;
Vector3 out;
double theta = Math.acos(Math.sqrt(((sigma2 / Math.sqrt(sigma4 + (1.0 - sigma4) * rnd.next())) - 1.0) / (sigma2 - 1.0)));
double phi = 2.0 * Math.PI * rnd.next();
SphericalCoordinates sc = new SphericalCoordinates(theta, phi);
Vector3 microN = sc.toCartesian(basis);
out = Optics.reflect(v, microN);
if (out.dot(N) <= 0.0) {
return null;
}
return out;
} else {
return Optics.refract(v, n1, n2, N);
}
}
}