openmesh_assimp.cpp

// assimp
#include <assimp/Importer.hpp>      // C++ importer interface
#include <assimp/scene.h>           // Output data structure
#include <assimp/postprocess.h>     // Post processing flags
#include <assimp/Exporter.hpp>

// openmesh
#include <OpenMesh/Core/IO/MeshIO.hh>
#include <OpenMesh/Core/Mesh/PolyMesh_ArrayKernelT.hh>


    
    // write to buffer
    size_t length = 200 * mesh_cloud.number_of_vertices();
    std::cout << length << std::endl;
    auto pBuf = new char[length]; // allocate memory
    struct membuf: std::streambuf // derive because std::streambuf constructor is protected
    {
      membuf(char* p, size_t size) 
      {
          setp( p, p + size); // set start end end pointers
      }
      size_t written() {return pptr()-pbase();} // how many bytes were really written?
    };
    membuf sbuf( pBuf, length ); // our buffer object
    std::ostream out( &sbuf );   // stream using our buffer
    OpenMesh::IO::write_mesh(mesh_out, out, "obj");
    out.flush();
    std::cout << "Nr of written bytes: " << sbuf.written() << std::endl;
    // write with assimp
    Assimp::Importer importer;
    const aiScene* scene = importer.ReadFileFromMemory( pBuf, sbuf.written(), 
        aiProcess_Triangulate            |
        aiProcess_JoinIdenticalVertices  |
        aiProcess_SortByPType);
    if( !scene)
    {
      std::cerr << "import error" << std::endl;
    }
    else
    {
      Assimp::Exporter exporter;
      size_t exportFormatCount = exporter.GetExportFormatCount();
      const aiExportFormatDesc* format = nullptr;
      for (size_t i = 0; i < exportFormatCount; ++i)
      {
          if (strcmp("fbx",exporter.GetExportFormatDescription(i)->id))
          {
            format = exporter.GetExportFormatDescription(i);
            break;
          }
      }
      if (!format)
      {
        std::cerr << "cannot export fbx" << std::endl;
      }
      else
      {
        aiReturn ret = exporter.Export(scene, format->id, out_topograpy_mesh, scene->mFlags);
        std::cout << "export fbx done" << std::endl;
      }
    }
    delete pBuf; // free memory