carla/Docs/define_custom_props.md

How to add custom props to the Blueprint Library

Users can register their own props with .fbx format and make these props available through the existing Carla Blueprint Library API. Also, these props can be spawned, maintaining compatibility with semantic segmentation tags.

To do so, the following steps should be done:

1. Create a folder called FBXImporter inside Carla root folder.

2. Place all your props in .fbx format and its textures inside FBXImporter folder.

3. Inside the newly created FBXImporter folder, create a JSON File with the name of your package and with extension .PropRegistry.json. For example, YourPackageName.PropRegistry.json. It is also possible to define multiple prop registry files inside that folder if it is needed to organize props in separate packages.

4. For each prop registry file, store a JSON Array called definitions, which will contain JSON Objects with relevant information for importing a prop such as:

   • name: The name of your prop, this name is the one that will be registered in the Carla Blueprint Library.
   • source: The path to your .fbx file.
   • size: The size of your prop in terms of dimensions. The possible values are: tiny, small, medium, big and huge.
   • tag: The semantic segmentation tag.

   An example of a .PropRegistry.json file would be:

    {
      "definitions":
      [
        {
          "name": "Prop01",
          "size": "medium",
          "source": "SM_Prop_1.fbx",
          "tag": "Pole"
        },
        {
          "name": "Prop02",
          "size": "medium",
          "source": "SM_Prop_2.fbx",
          "tag": "Roads"
        }
      ]
    }
   

5. Finally, run the Python script import_fbx.py located inside Carla/Util folder. This script reads all .PropRegistry.json files inside the FBXImporter folder and, for each .fbx file defined in the registry, it will be cooked together with its textures by Unreal Engine and moved inside the Carla Content in the following path: Content/YourPackageName/Static/PropTag/PropName/PropSource. Furthermore, each defined prop will be also included in the Carla Blueprint Library, so they can be queried and spawned using the PythonAPI.