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#include<fstream>#include<vector>#include<string>#include<algorithm>#include<CGAL/Simple_cartesian.h>#include<CGAL/Polyhedron_incremental_builder_3.h>#include<CGAL/Polyhedron_3.h>#include<CGAL/IO/Polyhedron_iostream.h>typedef CGAL::Simple_cartesian<double> Kernel;typedef CGAL::Polyhedron_3<Kernel> Polyhedron;typedef Polyhedron::HalfedgeDS HalfedgeDS;// A modifier creating a triangle with the incremental builder.template<class HDS>class polyhedron_builder : public CGAL::Modifier_base<HDS> {public: std::vector<double> &coords; std::vector<int> &tris; polyhedron_builder( std::vector<double> &_coords, std::vector<int> &_tris ) : coords(_coords), tris(_tris) {} void operator()( HDS& hds) { typedef typename HDS::Vertex Vertex; typedef typename Vertex::Point Point; // create a cgal incremental builder CGAL::Polyhedron_incremental_builder_3<HDS> B( hds, true); B.begin_surface( coords.size()/3, tris.size()/3 ); // add the polyhedron vertices for( int i=0; i<(int)coords.size(); i+=3 ){ B.add_vertex( Point( coords[i+0], coords[i+1], coords[i+2] ) ); } // add the polyhedron triangles for( int i=0; i<(int)tris.size(); i+=3 ){ B.begin_facet(); B.add_vertex_to_facet( tris[i+0] ); B.add_vertex_to_facet( tris[i+1] ); B.add_vertex_to_facet( tris[i+2] ); B.end_facet(); } // finish up the surface B.end_surface(); }};// reads the first integer from a string in the form// "334/455/234" by stripping forward slashes and// scanning the resultint get_first_integer( const char *v ){ int ival; std::string s( v ); std::replace( s.begin(), s.end(), '/', ' ' ); sscanf( s.c_str(), "%d", &ival ); return ival;}// barebones .OFF file reader, throws away texture coordinates, normals, etc.// stores results in input coords array, packed [x0,y0,z0,x1,y1,z1,...] and// tris array packed [T0a,T0b,T0c,T1a,T1b,T1c,...]void load_obj( const char *filename, std::vector<double> &coords, std::vector<int> &tris ){ double x, y, z; char line[1024], v0[1024], v1[1024], v2[1024]; // open the file, return if open fails FILE *fp = fopen(filename, "r" ); if( !fp ) return; // read lines from the file, if the first character of the // line is 'v', we are reading a vertex, otherwise, if the // first character is a 'f' we are reading a facet while( fgets( line, 1024, fp ) ){ if( line[0] == 'v' ){ sscanf( line, "%*s%lf%lf%lf", &x, &y, &z ); coords.push_back( x ); coords.push_back( y ); coords.push_back( z ); } else if( line[0] == 'f' ){ sscanf( line, "%*s%s%s%s", v0, v1, v2 ); tris.push_back( get_first_integer( v0 )-1 ); tris.push_back( get_first_integer( v1 )-1 ); tris.push_back( get_first_integer( v2 )-1 ); } } fclose(fp); }int main() { // two vectors to hold point coordinates and // triangle vertex indices std::vector<double> coords; std::vector<int> tris; // load the input file load_obj( "input.obj", coords, tris ); if( coords.size() == 0 ) return 1; // build a polyhedron from the loaded arrays Polyhedron P; polyhedron_builder<HalfedgeDS> builder( coords, tris ); P.delegate( builder ); // write the polyhedron out as a .OFF file std::ofstream os("dump.off"); os << P; os.close(); return 0;} |
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원본
http://jamesgregson.blogspot.kr/2012/05/example-code-for-building.html
Example code for building CGAL::Polyhedron_3
I've found myself redoing this code relatively frequently, so I thought I would post it. Nothing special, just a snippet that loads the file input.obj, builds a CGAL::Polyhedron_3 from it, and writes it out as dump.off. The code also includes a rudimentary Wavefront OBJ loader.
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