Function find_generation_point 

pub fn find_generation_point<F>(
    rng: &mut LegacyRandom,
    chunk_x: i32,
    chunk_z: i32,
    height: &HeightProviderData,
    min_gen_y: i32,
    gen_depth: i32,
    solid_block_below_air: F,
) -> Option<FossilResult>
where
    F: FnMut(i32, i32, i32, i32) -> Option<i32>,

Vanilla’s RNG sequence. Returns None if no air-over-solid transition above sea level.