final static String getXYZFromMatrix(Matrix4f mat, boolean allPositive) {
    String str = "";
    float[] row = new float[4];
    for (int i = 0; i < 3; i++) {
      mat.getRow(i, row);
      String term = "";
      if (row[0] != 0)
        term += (row[0] < 0 ? "-" : "+") + "x";
      if (row[1] != 0)
        term += (row[1] < 0 ? "-" : "+") + "y";
      if (row[2] != 0)
        term += (row[2] < 0 ? "-" : "+") + "z";
      term += xyzFraction(row[3], allPositive);
      if (term.length() > 0 && term.charAt(0) == '+')
        term = term.substring(1);
      str += "," + term;
    }
    return str.substring(1);
  }