# File ../lib/roller/CWRP.rb, line 948
  def apply_bumpiness(bumpiness)
    raise ArgumentError, "Bumpiness must be > 0" unless bumpiness > 0

    reset_progress 'Applying bumpiness', @terrain_height.size
    
    @terrain_height.each do |row|
      row.map! { |height| height + ((rand() - rand()) * bumpiness) }
      increment_progress
    end

    nil
  end