Function iterate_noise_column_capped 

fn iterate_noise_column_capped<N: DimensionNoises>(
    cache: &mut N::ColumnCache,
    noises: &N,
    aquifer: &mut Aquifer<N>,
    block_x: i32,
    block_z: i32,
    max_y_inclusive: i32,
    ocean_floor: bool,
) -> i32

Same as iterate_noise_column_with_aquifer but only scans Y values up to max_y_inclusive. Used by base_height with an estimate from preliminary_surface_level + 16 to skip empty upper atmosphere — reducing cell-corner density evaluations from O(height) to O(estimate_depth).