迁移到UE4

1.将xml文件转成 _ue.xml 文件

2.通过内容浏览器导入虚幻编辑器，并生成蓝图 -> 通过拖拽 Actor 的方式（参考 mujoco_plugin ）

-> Source/URLab/Public/MuJoCo/Core/AMjManager.h 是一个参与者，通过它进行xml文件的加载

3.在场景中指定位置将蓝图实例化

hutb 引擎中默认使用的是 Python 3.7.7，位于 Engine/Binaries/ThirdParty/Python3/Win64 、UE 5.7 中默认使用的是 Python 3.11.8。

问题

• 虚幻中验证pip报错：

  FPlatformProcess::ExecProcess(*PythonPath, TEXT("-m pip --version"), &PipCheck, &PipOut, &PipErr);
  
    File "D:\hutb\Build\engine\Engine\Binaries\ThirdParty\Python3\Win64\lib\site-packages\pip\_internal\vcs\subversion.py", line 180, in __init__
      use_interactive = sys.stdin.isatty()
  AttributeError: 'NoneType' object has no attribute 'isatty'
  

  手动执行包的安装：

  python -m pip install trimesh numpy scipy
  

  就可以生成_ue.xml文件和meshes/*glb文件。

• 打包报错：UnrealBuildTool: ERROR: Non-editor build cannot depend on non-redistributable modules.

  原因：将一些编辑器相关的内容打包进来了，参考链接。

  解决：打开 Build/engine/UE4.sln，右键项目 UnrealBuildTool 进行生成。

  资产打包报错：

  LogAssetRegistry: Error: Package ../../../../../Unreal/CarlaUE4/Plugins/UnrealRoboticsLab/Content/Input/IA_TwistMove.uasset is too old
  LogAssetRegistry: Error: Package ../../../../../Unreal/CarlaUE4/Plugins/UnrealRoboticsLab/Content/Input/IMC_TwistControl.uasset is too old
  LogAssetRegistry: Error: Package ../../../../../Unreal/CarlaUE4/Plugins/UnrealRoboticsLab/Content/Materials/M_MuJoCo_Master.uasset is too old
  LogAssetRegistry: Error: Package ../../../../../Unreal/CarlaUE4/Plugins/UnrealRoboticsLab/Content/Demo/example_BP/M_HoverGlow.uasset is too old
  LogAssetRegistry: Error: Package ../../../../../Unreal/CarlaUE4/Plugins/UnrealRoboticsLab/Content/UI/WBP_MjCameraFeedEntry.uasset is too old
  LogAssetRegistry: Error: Package ../../../../../Unreal/CarlaUE4/Plugins/UnrealRoboticsLab/Content/UI/WBP_MjPropertyRow.uasset is too old
  LogAssetRegistry: Error: Package ../../../../../Unreal/CarlaUE4/Plugins/UnrealRoboticsLab/Content/UI/WBP_MjSimulate.uasset is too old
  LogAssetRegistry: Error: Package ../../../../../Unreal/CarlaUE4/Plugins/UnrealRoboticsLab/Content/Input/IA_TwistTurn.uasset is too old
  LogAssetRegistry: Error: Package ../../../../../Unreal/CarlaUE4/Plugins/UnrealRoboticsLab/Content/Demo/example_BP/BP_RandomActions.uasset is too old
  

  解决：在资源浏览器中删除资产。

• error C2039: "byte": is not a member "std" C++14 原因：mujoco 和 CoACD 使用的是 C++ 17 进行编译，而虚幻工程使用 C++ 14

  解决：将 C++ 17 的一些语法改为 C++ 14

  // Unreal\CarlaUE4\Plugins\UnrealRoboticsLab\third_party\install\MuJoCo\include\mujoco\mjspec.h
  // using mjByteVec     = std::vector<std:byte>;
  using mjByteVec     = std::vector<unsigned char>;
  
  // Unreal\CarlaUE4\Plugins\UnrealRoboticsLab\third_party\install\CoACD\include\CoACD\coacd.h
  void set_log_level(); // void set_log_level(std::string_view level);
  

• UnrealBuildTool: ERROR: Could not find definition for module 'GeometryFramework', (referenced via Target -> URLab.Build.cs)

  模块 GeometryFramework 位于 UE5 的Engine/Source/Runtime/GeometryFramework