How can I get the outer_loop of multiple faces?

Take this picture for reference:


Usually, I use the outer_loop of a face to get the geometrie of a “wall” (blue and white faces combined). In this case, there is a recess in the loop due the other face splitting the edge on the side. The BoundingBox I get after combining the faces on that “wall” to a group does only work in very specific situations. Any pointers?

require 'set'

module Example

  # @return [Array<Sketchup::Edge>]
  def self.entity_set_border(entities)
    # Collect all faces in selection set for fast lookup.
    selection_faces =

    # Collect all edges for the faces in the selection set for fast lookup.
    edges =
    selection_faces.each { |face| edges.merge(face.edges) }

    # Find the edges that connects to only one of the faces in the selection.
    border = { |edge|
      num_faces = edge.faces.count { |face| selection_faces.include?(face) }
      num_faces == 1


  # Example.select_selection_border
  def self.select_selection_border
    model = Sketchup.active_model
    border = self.entity_set_border(model.selection)

end # module

Thanks, that’s exactly what I needed, never made the connection of using the number of faces connected to the outer edges.

Thomas, doesn’t that code assume there are no holes in the faces? That is, an edge of a hole will also have only one connected face?

True that - hence the methods called “border” and not “outer_loop”.