ECollideFunc.java

/*
  JWildfire - an image and animation processor written in Java 
  Copyright (C) 1995-2011 Andreas Maschke

  This is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser 
  General Public License as published by the Free Software Foundation; either version 2.1 of the 
  License, or (at your option) any later version.
 
  This software is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without 
  even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 
  Lesser General Public License for more details.

  You should have received a copy of the GNU Lesser General Public License along with this software; 
  if not, write to the Free Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
  02110-1301 USA, or see the FSF site: http://www.fsf.org.
*/
package org.jwildfire.create.tina.variation;

import static org.jwildfire.base.mathlib.MathLib.M_1_PI;
import static org.jwildfire.base.mathlib.MathLib.M_PI;
import static org.jwildfire.base.mathlib.MathLib.acos;
import static org.jwildfire.base.mathlib.MathLib.cos;
import static org.jwildfire.base.mathlib.MathLib.fmod;
import static org.jwildfire.base.mathlib.MathLib.sin;
import static org.jwildfire.base.mathlib.MathLib.sqrt;

import org.jwildfire.base.Tools;
import org.jwildfire.create.tina.base.Layer;
import org.jwildfire.create.tina.base.XForm;
import org.jwildfire.create.tina.base.XYZPoint;

public class ECollideFunc extends VariationFunc {
  private static final long serialVersionUID = 1L;

  private static final String PARAM_NUM = "num";
  private static final String PARAM_A = "a";

  private static final String[] paramNames = { PARAM_NUM, PARAM_A };

  private int num = 1;
  private double a = 0.0;

  //Taking the square root of numbers close to zero is dangerous.  If x is negative
  //due to floating point errors we get NaN results.
  private double sqrt_safe(double x) {
    if (x <= 0.0)
      return 0.0;
    return sqrt(x);
  }

  @Override
  public void transform(FlameTransformationContext pContext, XForm pXForm, XYZPoint pAffineTP, XYZPoint pVarTP, double pAmount) {
    // eCollide by Michael Faber, http://michaelfaber.deviantart.com/art/eSeries-306044892
    double tmp = pAffineTP.y * pAffineTP.y + pAffineTP.x * pAffineTP.x + 1.0;
    double tmp2 = 2.0 * pAffineTP.x;
    double xmax = (sqrt_safe(tmp + tmp2) + sqrt_safe(tmp - tmp2)) * 0.5;
    double sinnu, cosnu;
    int alt;
    if (xmax < 1.0)
      xmax = 1.0;

    double t = pAffineTP.x / xmax;
    if (t > 1.0)
      t = 1.0;
    else if (t < -1.0)
      t = -1.0;
    double nu = acos(t); // -Pi < nu < Pi

    alt = (int) (nu * _eCn_pi);
    if (alt % 2 == 0)
      nu = alt * _pi_eCn + fmod(nu + _eCa_eCn, _pi_eCn);
    else
      nu = alt * _pi_eCn + fmod(nu - _eCa_eCn, _pi_eCn);
    if (pAffineTP.y <= 0.0)
      nu *= -1.0;
    sinnu = sin(nu);
    cosnu = cos(nu);
    pVarTP.x += pAmount * xmax * cosnu;
    pVarTP.y += pAmount * sqrt(xmax - 1.0) * sqrt(xmax + 1.0) * sinnu;
    if (pContext.isPreserveZCoordinate()) {
  pVarTP.z += pAmount * pAffineTP.z;
}
  }

  @Override
  public String[] getParameterNames() {
    return paramNames;
  }

  @Override
  public Object[] getParameterValues() {
    return new Object[] { num, a };
  }

  @Override
  public void setParameter(String pName, double pValue) {
    if (PARAM_NUM.equalsIgnoreCase(pName))
      num = limitIntVal(Tools.FTOI(pValue), 1, Integer.MAX_VALUE);
    else if (PARAM_A.equalsIgnoreCase(pName))
      a = limitVal(pValue, 0.0, 1.0);
    else
      throw new IllegalArgumentException(pName);
  }

  @Override
  public String getName() {
    return "eCollide";
  }

  private double _eCa, _eCn_pi, _eCa_eCn, _pi_eCn;

  @Override
  public void init(FlameTransformationContext pContext, Layer pLayer, XForm pXForm, double pAmount) {
    _eCn_pi = (double) num * M_1_PI;
    _pi_eCn = M_PI / (double) num;
    _eCa = M_PI * a;
    _eCa_eCn = _eCa / (double) num;
  }

}