This small example shows how to remove faces and vertices from a mesh.
We basically use the geometry created in First Steps - Building a cube.
If we want our mesh class to be able to remove vertices, faces or (half-) edges we have to extend the default traits for our mesh class. Vertices, faces and (half-)edges need the OpenMesh::Attributes::Status attribute which is used to hold the flag "deleted" if an element is deleted.
The struct which defines the mesh traits then looks like this:
struct MyTraits : public OpenMesh::DefaultTraits { VertexAttributes(OpenMesh::Attributes::Status); FaceAttributes(OpenMesh::Attributes::Status); EdgeAttributes(OpenMesh::Attributes::Status); };
After having created the geometry of the cube one can delete faces and vertices by simply calling delete_vertices() (delete_faces() or delete_edges() respectiely).
In this example we delete all faces excpet one and the corresponding vertices. The code looks like this
// Delete face 0 mesh.delete_face(fhandle[0], false); // ... face 2 mesh.delete_face(fhandle[2], false); // ... face 3 mesh.delete_face(fhandle[3], false); // ... face 4 mesh.delete_face(fhandle[4], false); // ... face 5 mesh.delete_face(fhandle[5], false); // If isolated vertices result in a face deletion // they have to be deleted manually. If you want this // to happen automatically, change the second parameter // to true. // Now delete the isolated vertices 0, 1, 2 and 3 mesh.delete_vertex(vhandle[0], false); mesh.delete_vertex(vhandle[1], false); mesh.delete_vertex(vhandle[2], false); mesh.delete_vertex(vhandle[3], false);
Now the deleted faces and vertices are marked as "deleted" internally. Call garbage_collection() to definitely remove them from memory.
// Delete all elements that are marked as deleted // from memory. mesh.garbage_collection();
The full source code of the example:
//============================================================================= // // OpenMesh // Copyright (C) 2001-2005 by Computer Graphics Group, RWTH Aachen // www.openmesh.org // //----------------------------------------------------------------------------- // // License // // This library is free software; you can redistribute it and/or modify it // under the terms of the GNU Library General Public License as published // by the Free Software Foundation, version 2. // // This library 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 // Library General Public License for more details. // // You should have received a copy of the GNU Library General Public // License along with this library; if not, write to the Free Software // Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. // //----------------------------------------------------------------------------- // // $Revision: 83 $ // $Date: 2009-02-27 17:31:45 +0100 (Fri, 27 Feb 2009) $ // //============================================================================= #include <iostream> // -------------------- OpenMesh #include <OpenMesh/Core/IO/MeshIO.hh> #include <OpenMesh/Core/Mesh/PolyMesh_ArrayKernelT.hh> #include <OpenMesh/Core/System/config.h> #include <OpenMesh/Core/Mesh/Status.hh> // ---------------------------------------------------------------------------- struct MyTraits : public OpenMesh::DefaultTraits { VertexAttributes(OpenMesh::Attributes::Status); FaceAttributes(OpenMesh::Attributes::Status); EdgeAttributes(OpenMesh::Attributes::Status); }; typedef OpenMesh::PolyMesh_ArrayKernelT<MyTraits> MyMesh; // ---------------------------------------------------------------------------- // Build a simple cube and delete it except one face int main() { MyMesh mesh; // generate vertices MyMesh::VertexHandle vhandle[8]; MyMesh::FaceHandle fhandle[6]; vhandle[0] = mesh.add_vertex(MyMesh::Point(-1, -1, 1)); vhandle[1] = mesh.add_vertex(MyMesh::Point( 1, -1, 1)); vhandle[2] = mesh.add_vertex(MyMesh::Point( 1, 1, 1)); vhandle[3] = mesh.add_vertex(MyMesh::Point(-1, 1, 1)); vhandle[4] = mesh.add_vertex(MyMesh::Point(-1, -1, -1)); vhandle[5] = mesh.add_vertex(MyMesh::Point( 1, -1, -1)); vhandle[6] = mesh.add_vertex(MyMesh::Point( 1, 1, -1)); vhandle[7] = mesh.add_vertex(MyMesh::Point(-1, 1, -1)); // generate (quadrilateral) faces std::vector<MyMesh::VertexHandle> tmp_face_vhandles; tmp_face_vhandles.clear(); tmp_face_vhandles.push_back(vhandle[0]); tmp_face_vhandles.push_back(vhandle[1]); tmp_face_vhandles.push_back(vhandle[2]); tmp_face_vhandles.push_back(vhandle[3]); fhandle[0] = mesh.add_face(tmp_face_vhandles); tmp_face_vhandles.clear(); tmp_face_vhandles.push_back(vhandle[7]); tmp_face_vhandles.push_back(vhandle[6]); tmp_face_vhandles.push_back(vhandle[5]); tmp_face_vhandles.push_back(vhandle[4]); fhandle[1] = mesh.add_face(tmp_face_vhandles); tmp_face_vhandles.clear(); tmp_face_vhandles.push_back(vhandle[1]); tmp_face_vhandles.push_back(vhandle[0]); tmp_face_vhandles.push_back(vhandle[4]); tmp_face_vhandles.push_back(vhandle[5]); fhandle[2] = mesh.add_face(tmp_face_vhandles); tmp_face_vhandles.clear(); tmp_face_vhandles.push_back(vhandle[2]); tmp_face_vhandles.push_back(vhandle[1]); tmp_face_vhandles.push_back(vhandle[5]); tmp_face_vhandles.push_back(vhandle[6]); fhandle[3] = mesh.add_face(tmp_face_vhandles); tmp_face_vhandles.clear(); tmp_face_vhandles.push_back(vhandle[3]); tmp_face_vhandles.push_back(vhandle[2]); tmp_face_vhandles.push_back(vhandle[6]); tmp_face_vhandles.push_back(vhandle[7]); fhandle[4] = mesh.add_face(tmp_face_vhandles); tmp_face_vhandles.clear(); tmp_face_vhandles.push_back(vhandle[0]); tmp_face_vhandles.push_back(vhandle[3]); tmp_face_vhandles.push_back(vhandle[7]); tmp_face_vhandles.push_back(vhandle[4]); fhandle[5] = mesh.add_face(tmp_face_vhandles); // And now delete all faces and vertices // except face (vh[7], vh[6], vh[5], vh[4]) // whose handle resides in fhandle[1] // Delete face 0 mesh.delete_face(fhandle[0], false); // ... face 2 mesh.delete_face(fhandle[2], false); // ... face 3 mesh.delete_face(fhandle[3], false); // ... face 4 mesh.delete_face(fhandle[4], false); // ... face 5 mesh.delete_face(fhandle[5], false); // If isolated vertices result in a face deletion // they have to be deleted manually. If you want this // to happen automatically, change the second parameter // to true. // Now delete the isolated vertices 0, 1, 2 and 3 mesh.delete_vertex(vhandle[0], false); mesh.delete_vertex(vhandle[1], false); mesh.delete_vertex(vhandle[2], false); mesh.delete_vertex(vhandle[3], false); // Delete all elements that are marked as deleted // from memory. mesh.garbage_collection(); // write mesh to output.obj try { if ( !OpenMesh::IO::write_mesh(mesh, "output.off") ) { std::cerr << "Cannot write mesh to file 'output.off'" << std::endl; return 1; } } catch( std::exception& x ) { std::cerr << x.what() << std::endl; return 1; } return 0; }
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