iPhone 3GS and newer have a stencil buffer which can be used since iOS 4. As I wanted a realtime shadow solution for iSDGE, I decided to use this possibility to impement shadow volumes. The silouette detection needed for this was very slow, but I hapily found a way to speed it up a lot. The bottleneck currently is the rendering of the shadow volume, as it changes all the time, which means that it also have to be updated for the gpu all the time.
However, the scene above has around 5k polygons and all of them throw a shadow, which is a result I am already quite happy with and something I wanted to show around, as I didn´t yet see stencil shadows on the iPhone, except some demo created be apple.