Problem with uiimageview???? Need help

[Ermenquarto]

Hey guys, I'm ermenquarto, sorry for my english cuz I'm italian....so the problem is the following, I'm developing my first application using xcode and I've a problem with uiimageview, i'm using the image of a space shuttle and when I hit the rocks that go against me, i can't skip them because even if I don't touch them, the square of my image touches it. So how can I edit thos square and maybe use a triangol (because the image is a space shuttle)?? Thank you very much I hope you understand my question!