I get stuck with Pushpull

Zergboy

Hello!
Few days ago I start to explore SketchUP with Ruby
And after breaking of my mind with "Google SketchUp Ruby API" and "Automatic SketchUP" by Matthew Scarpino I still have not found an answer - what is the logic of a pushpull method.

What I did.

mod = Sketchup.active_model 
ent = mod.entities
new_circle = ent.add_circle [0,0,0], [0,1,0], 50,3
new_face = ent.add_face new_circle

Here all is clear.
Then

new_face.pushpull 5

OK, face extends to right. And now I have 3D shape.
OK, now I'd like to continue this extension.

new_face.pushpull 5

But now face start to move to left . And if I repeat

new_face.pushpull 5

face will continue to moth to left
So - first pushpull move face to right and next and all another - to left.
What is the logic?

What I need - I'd like to have possibilities to apply pushpull to a particular face after any pushpull. And how to specify for pushpull method exactly that face I need to move?
(And sorry for my English )

Jim

PushPull always extrudes a Face along the face's normal. If you notice after the first pushpull, the original face is reversed, so the subsequent pushpull extrudes in the opposite direction.

You need to check the Face's normal and reverse the face before extruding, or just extrude in a negative direction.