Point-based rendering is a compact and efficient means of displayingcomplex geometry. For mobile devices which typically have limited CPU orfloating point speed, limited memory, no graphics hardware and a smalldisplay, a hierarchical packed point based representation of objectsis particularly well adapted. We introduce -grids, which are ageneralization of previous octree based representations and analyse theirmemory and rendering efficiency. By storing intermediate node attributes,our structure allows flexible rendering, permitting efficient local imagerefinement, required for example when zooming into very complex scenes.We also introduce a novel and efficient one-pass shadow mapping algorithm usingthis data structure. We show an implementation of our method on a PDA,which can render objects sampled by 1.3 million points at 2.1 frames per second;the model was originally made up of 4.7 million polygons
