Blender 2.68: Physics
Use Modifier Stack
The Emission panel now has a Use Modifier Stack option to emit particles from the mesh with modifiers applied. Previously particles would only be emitted from faces that exist in the original mesh. Emitting from faces in the original mesh is mostly useful for hair, to preserve it through mesh editing operations and changing subdivision surfaces levels for viewport and rendering. For emitter particles it can be more useful to take all modifiers into account, but one must be careful to always use the same number of subdivision surface levels for this to work correctly. (Template:Commit)
Normal-Tangent rotation mode added, so you can control the orientation around the normal based on the faces UV coordinates, so particles and object instances stick to the mesh surface during deformation. (Template:Commit)
A new Full Sample" option was added to high resolution smoke panel. (Template:Commit)
When high resolution and full sample are enabled, the emitters now take the finer grid into account. Before the emitters where showing the blocks of the normal resolution grid even when the additional high resolution was enabled. This allows to use a lower base resolution for the simulation in many cases.
Emitters now have a "Subframes" option, for fast fast moving emitters. This allows for a smooth flow of smoke or fire even for emitters moving very fast. Previously, one puff of smoke was emitted for every frame, resulting in disjoint spots of smoke.