When using Blender Game Engine there are several methods for aligning objects orientations to sitting surface. One such popular method is to use Ray sensor and Python codes to align objects. With newer Blender for Dynamics objects, it is actually possible to align objects just by using Physics settings in object’s Material tab to orient sitting objects without using any Python codes. To do that you have to change values in the Physics of Material tab of the surface object you want objects to be orient to, especially values of Force, Damp and Distance like shown below. And for objects which should be oriented you have to tick Rotate from Normal in the Physics tab. If all set your objects will follow the orientation of the surface. Check out the sample blend file to see how it works, press A and D keyboard keys to move the object.
object_alignment.blend
object_alignment.blend
Physics settings in the material tab
