iSDGE is an open source 3D game engine for iPhone, iPad and iPod Touch. It is based on iOS 4 and under steady developement. Currently it only features rendering of 2D and 3D objects and no physics, audio or networking yet. It offers a flexible and easy to use shader system using OpenGL ES 2.0. A powerfull terrain system and a fast stencil shadow implementation. The focus is on speed and especially ease of use. The engine is mostly written in C++ and one small part in Objective-C. iSDGE features its own fast to load model format and comes with a exporter for Blender.
This video is taken from within the slow iPhone simulator and runs with stable 60fps on my iPhone 3GS. However the lod change distances are very close, so it will perform a little bit worse in a real scenerio, where one could on the otherhand also use less polygons close to the camera, so it should basicly still work just fine.
The water uses render to texture to render everything obe its surface for the reflections and moves with the camera to cause the illusion of an endless ocean with few polygons and only little precision problems on the real device. The terrain uses a big color textures with a tiled greyscale detail texture above it to add some general detail.