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APSF.h

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+///////////////////////////////////////////////////////////////////////////////////
+// File : APSF.h
+///////////////////////////////////////////////////////////////////////////////////
+//
+// LumosQuad - A Lightning Generator
+// Copyright 2007
+// The University of North Carolina at Chapel Hill
+// 
+///////////////////////////////////////////////////////////////////////////////////
+//
+//  This program is free software; you can redistribute it and/or modify
+//  it under the terms of the GNU General Public License as published by
+//  the Free Software Foundation; either version 2 of the License, or
+//  (at your option) any later version.
+//
+//  This program 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 General Public License for more details.
+// 
+//  You should have received a copy of the GNU General Public License
+//  along with this program; if not, write to the Free Software
+//  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+//
+//  The University of North Carolina at Chapel Hill makes no representations 
+//  about the suitability of this software for any purpose. It is provided 
+//  "as is" without express or implied warranty.
+//
+//  Permission to use, copy, modify and distribute this software and its
+//  documentation for educational, research and non-profit purposes, without
+//  fee, and without a written agreement is hereby granted, provided that the
+//  above copyright notice and the following three paragraphs appear in all
+//  copies.
+//
+//  THE UNIVERSITY OF NORTH CAROLINA SPECIFICALLY DISCLAIM ANY WARRANTIES,
+//  INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
+//  FITNESS FOR A PARTICULAR PURPOSE.  THE SOFTWARE PROVIDED HEREUNDER IS ON AN
+//  "AS IS" BASIS, AND THE UNIVERSITY OF NORTH CAROLINA HAS NO OBLIGATION TO
+//  PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
+//
+//  Please send questions and comments about LumosQuad to kim@cs.unc.edu.
+//
+///////////////////////////////////////////////////////////////////////////////////
+//
+//  This program uses OpenEXR, which has the following restrictions:
+// 
+//  Copyright (c) 2002, Industrial Light & Magic, a division of Lucas
+//  Digital Ltd. LLC
+// 
+//  All rights reserved.
+// 
+//  Redistribution and use in source and binary forms, with or without
+//  modification, are permitted provided that the following conditions are
+//  met:
+//  *       Redistributions of source code must retain the above copyright
+//  notice, this list of conditions and the following disclaimer.
+//  *       Redistributions in binary form must reproduce the above
+//  copyright notice, this list of conditions and the following disclaimer
+//  in the documentation and/or other materials provided with the
+//  distribution.
+//  *       Neither the name of Industrial Light & Magic nor the names of
+//  its contributors may be used to endorse or promote products derived
+//  from this software without specific prior written permission. 
+// 
+
+#ifndef APSF_H
+#define APSF_H
+
+#include <cmath>
+#include <GL/glut.h>
+#include <vector>
+#include "ppm/ppm.hpp"
+
+using namespace std;
+
+#ifndef M_PI
+#define M_PI 3.1415926535897931f
+#endif
+
+////////////////////////////////////////////////////////////////////
+/// \brief Generates the rendering filter
+////////////////////////////////////////////////////////////////////
+class APSF  
+{
+public:
+  //! constructor
+	APSF(int res = 512);
+  //! destructor
+	virtual ~APSF();
+
+  //! read in an APSF file
+  void read(const char* filename);
+  //! write out an APSF file
+  void write(const char* filename);
+  //! write out the current kernel to a PPM file
+  void writePPM(const char* filename);
+  
+  //! generate one line of the kernel and spin it radially
+  void generateKernelFast();
+
+  //! resolution of current kernel
+  int res() { return _res; };
+  
+  //! returns the float array for the kernel
+  float* kernel() { return _kernel; };
+  
+private:
+  //! kernel resolution
+  int     _res;
+  //! convolution kernel
+  float*  _kernel;
+
+  ////////////////////////////////////////////////////////////////////
+  // APSF components
+  ////////////////////////////////////////////////////////////////////
+
+  // scattering parameters
+  float _q;
+  float _T;
+  float _I0;
+  float _sigma;
+  float _R;
+  float _D;
+
+  float _retinaSize;
+  float _eyeSize;
+  
+  //! number of coefficients
+  int _maxTerms;
+  
+  //! function value at a point
+  float pointAPSF(float mu);
+  
+  ////////////////////////////////////////////////////////////////////
+  // auxiliary functions
+  ////////////////////////////////////////////////////////////////////
+  float legendreM(int m, float mu);
+  float gM(float I0, int m) {
+    return (m == 0) ? 0.0f : exp(-(betaM(m, _q) * _T + alphaM(m) * log(_T)));
+  };
+  float alphaM(float m) { 
+    return m + 1.0f;
+  };
+  float betaM(float m, float q) {
+    return ((2.0f * m + 1.0f) / m) * (1.0f - pow(q, (int)m - 1));
+  };
+  float factorial(float x) {
+    return (x <= 1.0f) ? 1.0f : x * factorial(x - 1.0f);
+  };
+  float choose(float x, float y) {
+    return factorial(x) / (factorial(y) * factorial(x - y));
+  };
+};
+
+#endif