This example is the first version of the simple mesh smoother. Here we will introduce iterators and circulators. These two concepts provide functionality to linearly enumerate e.g. all vertices of a mesh, and to circulate around a vertex, i.e. to enumerate all its one-ring neighbors. For a more detailed description, see Mesh Iterators and Circulators.
First we have to define the mesh type we want to use. This time we use a triangle mesh instead of a polygonal mesh:
#include <OpenMesh/Core/Mesh/Types/TriMesh_ArrayKernelT.hh> typedef OpenMesh::TriMesh_ArrayKernelT<> MyMesh;
We read the mesh to be smoothed from a file:
if ( ! OpenMesh::IO::read_mesh(mesh, argv[2]) )
One smoothing iteration is done in two steps:
This can easily be implemented using vertex iterators. The mesh provides begin and end iterators by vertices_begin()
and vertices_end()
.
MyMesh::VertexIter v_it, v_end(mesh.vertices_end()); for (v_it=mesh.vertices_begin(); v_it!=v_end; ++v_it)
For calculating the barycenter, we have to iterate through the one-ring neighborhood of the current vertex. This functionality is provided by the VertexVertexIter
:
MyMesh::VertexVertexIter vv_it; for (vv_it=mesh.vv_iter( v_it ); vv_it; ++vv_it)
Now we can calculate the barycenters for each vertex and store them in the array cogs
:
std::vector<MyMesh::Point> cogs; for (v_it=mesh.vertices_begin(); v_it!=v_end; ++v_it) { cog[0] = cog[1] = cog[2] = valence = 0.0; for (vv_it=mesh.vv_iter( v_it ); vv_it; ++vv_it) { cog += mesh.point( vv_it ); ++valence; } cogs.push_back(cog / valence); }
After we have calculated the barycenters all that is left to do is to move the vertices to the corresponding barycenters. The complete source code is listed below.
#include <iostream> #include <vector> // -------------------- OpenMesh #include <OpenMesh/Core/IO/MeshIO.hh> #include <OpenMesh/Core/Mesh/Types/TriMesh_ArrayKernelT.hh> typedef OpenMesh::TriMesh_ArrayKernelT<> MyMesh; int main(int argc, char **argv) { MyMesh mesh; // check command line options if (argc != 4) { std::cerr << "Usage: " << argv[0] << " #iterations infile outfile\n"; return 1; } // read mesh from stdin if ( ! OpenMesh::IO::read_mesh(mesh, argv[2]) ) { std::cerr << "Error: Cannot read mesh from " << argv[2] << std::endl; return 1; } // this vector stores the computed centers of gravity std::vector<MyMesh::Point> cogs; std::vector<MyMesh::Point>::iterator cog_it; cogs.reserve(mesh.n_vertices()); // smoothing mesh argv[1] times MyMesh::VertexIter v_it, v_end(mesh.vertices_end()); MyMesh::VertexVertexIter vv_it; MyMesh::Point cog; MyMesh::Scalar valence; unsigned int i, N(atoi(argv[1])); for (i=0; i < N; ++i) { cogs.clear(); for (v_it=mesh.vertices_begin(); v_it!=v_end; ++v_it) { cog[0] = cog[1] = cog[2] = valence = 0.0; for (vv_it=mesh.vv_iter( v_it ); vv_it; ++vv_it) { cog += mesh.point( vv_it ); ++valence; } cogs.push_back(cog / valence); } for (v_it=mesh.vertices_begin(), cog_it=cogs.begin(); v_it!=v_end; ++v_it, ++cog_it) if ( !mesh.is_boundary( v_it ) ) mesh.set_point( v_it, *cog_it ); } // write mesh to stdout if ( ! OpenMesh::IO::write_mesh(mesh, argv[3]) ) { std::cerr << "Error: cannot write mesh to " << argv[3] << std::endl; return 1; } return 0; }