progress.push_task_slice("Computing TBN", 0, prog_count)
self.split_vertices(self.find_uv_group, progress, tbn_layer_index)
progress.set_task_slice(self.tbn_uvtex, 1, prog_count)
progress.push_task_slice("Computing TBN", 0, prog_count)
self.split_vertices(self.find_uv_group, progress, tbn_layer_index)
progress.set_task_slice(self.tbn_uvtex, 1, prog_count)