ERotateFunc.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_2PI;
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.create.tina.base.XForm;
import org.jwildfire.create.tina.base.XYZPoint;

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

  private static final String PARAM_ROTATE = "rotate";

  private static final String[] paramNames = { PARAM_ROTATE };

  private double rotate = 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) {
    // eRotate 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;
    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
    if (pAffineTP.y < 0)
      nu *= -1.0;

    nu = fmod(nu + rotate + M_PI, M_2PI) - M_PI;

    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[] { rotate };
  }

  @Override
  public void setParameter(String pName, double pValue) {
    if (PARAM_ROTATE.equalsIgnoreCase(pName))
      rotate = pValue;
    else
      throw new IllegalArgumentException(pName);
  }

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

}