su-transformation-helper.rb

# http://stackoverflow.com/a/17982272/816093

module TransformationHelper

  def flipped_x?
    dot_x, dot_y, dot_z = axes_dot_products()
    dot_x < 0 && flipped?(dot_x, dot_y, dot_z)
  end

  def flipped_y?
    dot_x, dot_y, dot_z = axes_dot_products()
    dot_y < 0 && flipped?(dot_x, dot_y, dot_z)
  end

  def flipped_z?
    dot_x, dot_y, dot_z = axes_dot_products()
    dot_z < 0 && flipped?(dot_x, dot_y, dot_z)
  end

  private

  def axes_dot_products
    [
      xaxis.dot(X_AXIS),
      yaxis.dot(Y_AXIS),
      zaxis.dot(Z_AXIS)
    ]
  end

  def flipped?(dot_x, dot_y, dot_z)
    dot_x * dot_y * dot_z < 0
  end

end


module Example

  def self.inspect_flipped
    tr = Sketchup.active_model.selection[0].transformation
    tr.extend(TransformationHelper)

    puts "X Flipped: #{tr.flipped_x?.inspect}"
    puts "Y Flipped: #{tr.flipped_y?.inspect}"
    puts "Z Flipped: #{tr.flipped_z?.inspect}"
  end

end