Function veloren_world::sim::erosion::get_rivers

pub fn get_rivers<F: Debug + Float + Into<f64>, G: Float + Into<f64>>(
    map_size_lg: MapSizeLg,
    continent_scale_hack: f64,
    newh: &[u32],
    water_alt: &[F],
    downhill: &[isize],
    indirection: &[i32],
    drainage: &[G]
) -> Box<[RiverData]>

Draw rivers and assign them heights, widths, and velocities. Take some liberties with the constant factors etc. in order to make it more likely that we draw rivers at all.