message: Support specifying multiple 3D model files
diff: #include <map>
  #include <memory>
  #include <new>
  +#include <set>
  #include <sstream>
  #include <string>
  #include <thread>
  @@ -124,13 +125,12 @@ struct renderer : viewer_type
  {
  using namespace support;
  - add_cmdline_option( cl::makeOption<std::string&>(
  + add_cmdline_option( cl::makeOption<std::set<std::string>&>(
  cl::Parser<>(),
  - "filename",
  - cl::Desc("Input file in wavefront obj format"),
  + "filenames",
  + cl::Desc("Input files in wavefront obj format"),
  cl::Positional,
  - cl::Required,
  - cl::init(this->filename)
  + cl::init(filenames)
  ) );
  add_cmdline_option( cl::makeOption<std::string&>(
  @@ -232,7 +232,7 @@ struct renderer : viewer_type
  bool show_bvh = false;
  - std::string filename;
  + std::set<std::string> filenames;
  std::string initial_camera;
  model mod;
  @@ -718,11 +718,14 @@ int main(int argc, char** argv)
  // Load the scene
  std::cout << "Loading model...\n";
  - if (!rend.mod.load(rend.filename))
  + for (auto filename : rend.filenames)
  + {
  + if (!rend.mod.load(filename))
  {
  std::cerr << "Failed loading model\n";
  return EXIT_FAILURE;
  }
  + }
  // timer t;
  