vcglib/wrap/gl/glu_tesselator.h

/****************************************************************************
* VCGLib                                                            o o     *
* Visual and Computer Graphics Library                            o     o   *
*                                                                _   O  _   *
* Copyright(C) 2004                                                \/)\/    *
* 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.                                                         *
*                                                                           *
****************************************************************************/
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#ifndef __VCGLIB_GLU_TESSELATOR_H
#define __VCGLIB_GLU_TESSELATOR_H

#include <vector>
#include <GL/glu.h>

namespace vcg
{

class glu_tesselator
{
	public:

		typedef glu_tesselator this_type;

		/*
			Works with Point2 and Point3;

			sample usage:

			// tesselation input: each outline represents a polygon contour
			std::vector< std::vector<point_type> > outlines = ...;

			// tesselation output (triangles indices)
			std::vector<int> indices;

			// compute triangles indices
			glu_tesselator::tesselate(outlines, indices);

			// unroll input contours points
			std::vector<point_type> points;

			for (size_t i=0; i<outlines.size(); ++i)
			{
				for (size_t j=0; j<outlines[i].size(); ++j)
				{
					points.push_back(outlines[i][j]);
				}
			}
			// or simply call glu_tesselator::unroll(outlines, points);

			// create triangles
			for (size_t i=0; i<indices.size(); i+=3)
			{
				create_triangle(
					points[ indices[i+0] ],
					points[ indices[i+1] ],
					points[ indices[i+2] ]);
			}
		*/

		template <class point_type>
		static inline void unroll(const std::vector< std::vector<point_type> > & outlines, std::vector<point_type> & points)
		{
			for (size_t i=0; i<outlines.size(); ++i)
			{
				for (size_t j=0; j<outlines[i].size(); ++j)
				{
					points.push_back(outlines[i][j]);
				}
			}
		}

		template <class point_type>
		static inline void tesselate(const std::vector< std::vector<point_type> > & outlines, std::vector<int> & indices)
		{
			tess_prim_data_vec t_data;

			this_type::do_tesselation(outlines, t_data);

			int k = 0;
			for (size_t i=0; i<t_data.size(); ++i)
			{
				const size_t st = t_data[i].indices.size();
				if (st < 3) continue;

				switch (t_data[i].type)
				{
					case GL_TRIANGLES:
						for (size_t j=0; j<st; ++j)
						{
							indices.push_back(t_data[i].indices[j]);
						}
						break;

					case GL_TRIANGLE_STRIP:
						{
						int i0 = t_data[i].indices[0];
						int i1 = t_data[i].indices[1];

						bool ccw = true;

						for (size_t j=2; j<st; ++j)
						{
							const int i2 = t_data[i].indices[j];

							indices.push_back(i0);
							indices.push_back(i1);
							indices.push_back(i2);

							if (ccw) i0 = i2;
							else     i1 = i2;

							ccw = !ccw;
						}																	}
						break;

					case GL_TRIANGLE_FAN:
						{
						const int first = t_data[i].indices[0];
						int prev = t_data[i].indices[1];

						for (size_t j=2; j<st; ++j)
						{
							const int curr = t_data[i].indices[j];

							indices.push_back(first);
							indices.push_back(prev);
							indices.push_back(curr);

							prev = curr;
						}
						}
						break;

					default:
						break;
				}
			}
		}

	protected:

		class tess_prim_data
		{
			public:

				typedef tess_prim_data this_type;

				GLenum type;
				std::vector<int> indices;

				tess_prim_data(void) { }
				tess_prim_data(GLenum t) : type(t) { }
		};

		typedef std::vector<tess_prim_data> tess_prim_data_vec;

		static void CALLBACK begin_cb(GLenum type, void * polygon_data)
		{
			tess_prim_data_vec * t_data = (tess_prim_data_vec *)polygon_data;
			t_data->push_back(tess_prim_data(type));
		}

		static void CALLBACK end_cb(void * polygon_data)
		{
			(void)polygon_data;
		}

		static void CALLBACK vertex_cb(void * vertex_data, void * polygon_data)
		{
			tess_prim_data_vec * t_data = (tess_prim_data_vec *)polygon_data;
			t_data->back().indices.push_back((int)vertex_data);
		}

		template <class point_type>
		static void do_tesselation(const std::vector< std::vector<point_type> > & outlines, tess_prim_data_vec & t_data)
		{
			GLUtesselator * tess = gluNewTess();

			gluTessCallback(tess, GLU_TESS_BEGIN_DATA,  (void (CALLBACK *)(void))(this_type::begin_cb));
			gluTessCallback(tess, GLU_TESS_END_DATA,    (void (CALLBACK *)(void))(this_type::end_cb));
			gluTessCallback(tess, GLU_TESS_VERTEX_DATA, (void (CALLBACK *)(void))(this_type::vertex_cb));

			void * polygon_data = (void *)(&t_data);

			GLdouble vertex[3];

			int k = 0;
			gluTessBeginPolygon(tess, polygon_data);
			for (size_t i=0; i<outlines.size(); ++i)
			{
				gluTessBeginContour(tess);
				for (size_t j=0; j<outlines[i].size(); ++j)
				{
					this_type::get_position(outlines[i][j], vertex);
					gluTessVertex(tess, vertex, (void *)k);
					++k;
				}
				gluTessEndContour(tess);
			}
			gluTessEndPolygon(tess);

			gluDeleteTess(tess);
		}

		template <class scalar_type>
		static inline void get_position(const vcg::Point2<scalar_type> & p, GLdouble * d)
		{
			d[0] = (GLdouble)(p[0]);
			d[1] = (GLdouble)(p[1]);
			d[2] = (GLdouble)(0);
		}

		template <class scalar_type>
		static inline void get_position(const vcg::Point3<scalar_type> & p, GLdouble * d)
		{
			d[0] = (GLdouble)(p[0]);
			d[1] = (GLdouble)(p[1]);
			d[2] = (GLdouble)(p[2]);
		}
};

} // end namespace vcg

#endif // __VCGLIB_GLU_TESSELATOR_H