message: Load first camera from cams.json in Batch
diff: #include "sg/visitors/PrintNodes.h"
  // rkcommon
  #include "rkcommon/utility/SaveImage.h"
  +// cerealization
  +#include <cereal/archives/json.hpp>
  +#include <cereal/types/memory.hpp>
  +#include <cereal/types/vector.hpp>
  // Batch mode entry point
  void start_Batch_mode(int argc, const char *argv[])
  @@ -150,6 +154,15 @@ void BatchContext::render()
  // Update camera based on world bounds after import
  arcballCamera.reset(new ArcballCamera(frame["world"].bounds(), optImageSize));
  + std::ifstream cams("cams.json");
  + if (cams) {
  + std::vector<CameraState> cameraStack;
  + cereal::JSONInputArchive iarchive(cams);
  + iarchive(cameraStack);
  + CameraState cs = cameraStack.front();
  + arcballCamera->setState(cs);
  + }
  +
  auto &camera = frame.child("camera");
  if (camera.hasChild("aspect"))
  camera["aspect"] = optImageSize.x / (float)optImageSize.y;
  