What is the box_warp here means?

[bobfacer]

Thanks for your great excellent work.I have a little question about this params in the code box_warp,It seems that you use this params to scale the coordinates,in your conf,you set this params to be 3,It is in the triplane_pet.py:

def sample_from_planes(plane_axes, plane_features, coordinates, mode='bilinear', padding_mode='zeros', box_warp=None):
    assert padding_mode == 'zeros'
    N, n_planes, C, H, W = plane_features.shape
    _, M, _ = coordinates.shape
    plane_features = plane_features.view(N*n_planes, C, H, W)

    coordinates = (2/box_warp) * coordinates #why?

    projected_coordinates = project_onto_planes(plane_axes, coordinates).unsqueeze(1)
    output_features = grid_sample.grid_sample_2d(plane_features, projected_coordinates.float()).permute(0, 3, 2, 1).reshape(N, n_planes, M, C) 

    return output_features #[1, 3, num_points, channels]

I want to know why have to do like that,thank you!