message: Make node's exported creation functions dllexport for windows
diff: // xml
  #include "../../../common/xml/XML.h"
  // ospcommon
  +#include "ospray/common/OSPCommon.h"
  #include "ospcommon/vec.h"
  #include "mapbox/variant.hpp"
  #include <mutex>
  @@ -584,7 +585,7 @@ namespace ospray {
  of this renderer.
  */
  #define OSP_REGISTER_SG_NODE(InternalClassName) \
  - extern "C" std::shared_ptr<ospray::sg::Node> \
  + extern "C" OSPRAY_DLLEXPORT std::shared_ptr<ospray::sg::Node> \
  ospray_create_sg_node__##InternalClassName() \
  { \
  std::cout << "creating Node of type: " << typeid(ospray::sg::InternalClassName).name() << std::endl; \
  @@ -592,7 +593,7 @@ namespace ospray {
  }
  #define OSP_REGISTER_SG_NODE_NAME(InternalClassName,Name) \
  - extern "C" std::shared_ptr<ospray::sg::Node> ospray_create_sg_node__##Name() \
  + extern "C" OSPRAY_DLLEXPORT std::shared_ptr<ospray::sg::Node> ospray_create_sg_node__##Name() \
  { \
  std::cout << "creating Node of type: " << typeid(ospray::sg::InternalClassName).name() << std::endl; \
  return std::make_shared<ospray::sg::InternalClassName>(); \
  