   HLSL Motion Blur Tutorials?
  I'm attempting to implement some basic motion blur using HLSL, and I'm having trouble finding tutorials that start simple and have some code examples.  From what I can gather, motion blur is done by either rendering the velocity to a buffer and using that later for post processing blurring, or by using the depth buffer to calculate velocity (which I can't even make sense of).  Beyond that, I'm sorta stuck.  Anyone know of any good tutorials for beginners?   