XBPageCurl is a free and open-source implementation of a page curl animation/transition for views in iOS that intends to mimic the behavior of the pages in apps like iBooks and GoogleMaps for iOS. It uses OpenGL ES 2.0 to draw a deformed mesh of triangles. Conceptually, it projects the vertices of the mesh on a virtual cylinder that rolls on the view. You can move, rotate and change the radius of the cylinder, with or without animation. The mesh follows the cylinder as it moves. The mesh deformation is performed in a crazy vertex shader which makes it really fast.