vcglib/vcg/space/index/grid_util.h

/****************************************************************************
* VCGLib                                                            o o     *
* Visual and Computer Graphics Library                            o     o   *
*                                                                _   O  _   *
* Copyright(C) 2005                                                \/)\/    *
* Visual Computing Lab                                            /\/|      *
* ISTI - Italian National Research Council                           |      *
*                                                                    \      *
* All rights reserved.                                                      *
*                                                                           *
* 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 (http://www.gnu.org/licenses/gpl.txt)          *
* for more details.                                                         *
*                                                                           *
****************************************************************************/
/****************************************************************************
History

$Log: not supported by cvs2svn $
Revision 1.4  2005/08/02 11:01:05  pietroni
added IPToP and IBoxToBox functions, modified BoxToIBox function in order to use PToIP function

Revision 1.3  2005/07/28 06:11:12  cignoni
corrected error in GridP (did not compile)

Revision 1.2  2005/07/01 11:33:36  cignoni
Added a class BasicGrid with some utility function that are scattered among similar classes

Revision 1.1  2005/03/15 11:43:18  cignoni
Removed BestDim function from the grid_static_ptr class and moved to a indipendent file (grid_util.h) for sake of generality.


****************************************************************************/
#ifndef __VCGLIB_GRID_UTIL
#define __VCGLIB_GRID_UTIL


namespace vcg {

	// classe di base per tutte le strutture dati di indexing spaziale basate su griglia.
	// contiene tutte le funzioni solite per le conversioni tra point3f e point3i


	template <class ScalarType>
	class BasicGrid {

		typedef Box3<ScalarType> Box3x;

	public:
		Box3x bbox;
		/// Dimensione spaziale (lunghezza lati) del bbox
		Point3<ScalarType> dim;
		/// Dimensioni griglia in celle
		Point3i siz;
		/// Dimensioni di una cella
		Point3<ScalarType> voxel;



		// Dato un punto ritorna le coordinate della cella
		inline Point3i GridP( const Point3<ScalarType> & p ) const 
		{
			Point3i pi; 
			PToIP(p,pi);
			return pi;
		}


		/// Dato un punto 3d ritorna l'indice del box corrispondente
		inline void PToIP(const Point3<ScalarType> & p, Point3i &pi ) const
		{
			Point3<ScalarType> t = p - bbox.min;
			pi[0] = int( t[0]/voxel[0] );
			pi[1] = int( t[1]/voxel[1] );
			pi[2] = int( t[2]/voxel[2] );
		}

		/// Given a voxel index return the lower corner of the voxel
		inline void IPToP(const Point3i & pi, Point3<ScalarType> &p ) const
		{
			p[0] = ((ScalarType)pi[0])*voxel[0];
			p[1] = ((ScalarType)pi[1])*voxel[1];
			p[2] = ((ScalarType)pi[2])*voxel[2];
			p +=bbox.min;
		}

		/// Dato un box reale ritorna gli indici dei voxel compresi dentro un ibox
		void BoxToIBox( const Box3x & b, Box3i & ib ) const
		{
			PToIP(b.min,ib.min);
			PToIP(b.max,ib.max);
			assert(ib.max[0]>=0 && ib.max[1]>=0 && ib.max[2]>=0);	
		}

		/// Dato un box in voxel ritorna gli estremi del box reale
		void IBoxToBox( const Box3i & ib, Box3x & b ) const
		{
			IPtoP(ib.min,b.min);
			IPtoP(ib.max,b.max);
		}

	};

	/** Calcolo dimensioni griglia.
	Calcola la dimensione della griglia in funzione
	della ratio del bounding box e del numero di elementi
	*/
	template<class scalar_type>
		void BestDim( const int elems, const Point3<scalar_type> & size, Point3i & dim )
	{
		const int mincells   = 1;		// Numero minimo di celle
		const double GFactor = 1.0;	// GridEntry = NumElem*GFactor
		double diag = size.Norm();	// Diagonale del box
		double eps  = diag*1e-4;		// Fattore di tolleranza

		assert(elems>0);
		assert(size[0]>=0.0);
		assert(size[1]>=0.0);
		assert(size[2]>=0.0);


		int ncell = int(elems*GFactor);	// Calcolo numero di voxel
		if(ncell<mincells)
			ncell = mincells;

		dim[0] = 1;
		dim[1] = 1;
		dim[2] = 1;

		if(size[0]>eps)
		{
			if(size[1]>eps)
			{
				if(size[2]>eps)
				{
					double k = pow((double)(ncell/(size[0]*size[1]*size[2])),double(1.0/3.f));
					dim[0] = int(size[0] * k);
					dim[1] = int(size[1] * k);
					dim[2] = int(size[2] * k);
				} 
				else 
				{
					dim[0] = int(::sqrt(ncell*size[0]/size[1]));
					dim[1] = int(::sqrt(ncell*size[1]/size[0]));
				}
			}
			else
			{
				if(size[2]>eps)
				{
					dim[0] = int(::sqrt(ncell*size[0]/size[2]));
					dim[2] = int(::sqrt(ncell*size[2]/size[0]));
				}
				else
					dim[0] = int(ncell);
			}
		}
		else
		{
			if(size[1]>eps)
			{
				if(size[2]>eps)
				{
					dim[1] = int(::sqrt(ncell*size[1]/size[2]));
					dim[2] = int(::sqrt(ncell*size[2]/size[1]));
				}
				else
					dim[1] = int(ncell);
			}
			else if(size[2]>eps)
				dim[2] = int(ncell);
		}
		dim[0] = math::Max(dim[0],1);
		dim[1] = math::Max(dim[1],1);
		dim[2] = math::Max(dim[2],1);
	}
}
#endif