Positions obtained from vertices are always locale to their parent - not global.
In order to work out the global position you need the combined transformation for all the parent instances. How you do that depend on context of how your extension work.
For instance, if your extension works on the active_entities at all time, then you can obtain the transformation via model.edit_transform.
But if you are traversing the whole model, say if you do a model export, then you need to keep track of the instance transformations as you dig down into the model hierarchy.
module Example
def self.get_entities(instance)
if entity.is_a?(Sketchup::Group)
entity.entities
else
entity.definition.entities
end
end
def self.walk(entities, transformation = IDENTITY)
entities.each { |entity|
case entity
when Sketchup::Face
global_points = face.outer_loop.vertices.map { |vertex|
vertex.position.transform(transformation)
}
# Do stuff to global position of vertices here...
when Sketchup::Group, Sketchup::ComponentInstance
entities = get_entities(instance)
walk(entities, entity.transformation * transformation)
end
}
end
end