URDFLoader's load function incorrectly caches workingPath while being used in R3F useLoader

[smeng9]

Hi @gkjohnson ,

We have a use case in R3F with this library to load multiple URDF models based on a state variable.
Basically the minimal reproducible example looks like the following

  // We have multiple buttons at the bottom and user can select the urdf to render
  const [urdfPath, setURDFPath] = useState("model1/default.urdf")

  const object = useLoader(
    URDFLoader,
    `${apiUrl}/{urdfPath}`,
  );

  // Returns a list of buttons and a scene

In the first rendering the working path will be ${apiUrl}/model1. (See how THREE.LoaderUtils.extractUrlBase extracts workingPath https://github.com/gkjohnson/urdf-loaders/blob/master/javascript/src/URDFLoader.js#L89

In subsequent render user change the model to model2/robot.urdf. However the workingPath will not be updated https://github.com/gkjohnson/urdf-loaders/blob/master/javascript/src/URDFLoader.js#L115 and it uses the wrong model1 path to load the meshes for model2.

To apply the fix remove the if condition check.

Thanks~