newton-physics/newton

@eric-heiden @adenzler-nvidia ModelBuilder.add_usd() does not retain joint ordering of USD assets for non-articulated joints, and when no articulations are present, the joint_ordering has no effect. This is problematic as USD model authors may have intentional ordering of joints, but this will not be respected by the model builder. I propose that we modify the import_usd.parse_usd method to make use of the joint_ordering argument even for orphan joints. Specifically, we should first traverse the stage to make a list of joint prim paths and types, and then parse and extract the joint descriptors, filling in corresponding placeholder entries created by the stage traversal, e.g.: # First construct lists of joint prim paths and their types that # retain the order of the joints as specified in the USD file. joint_prim_paths = [] joint_type_names = [] for prim in stage.Traverse(): if prim.GetTypeName() in self.supported_usd_joint_type_names: joint_type_names.append(prim.GetTypeNa