Crepuscular Rays Post Process

So, I have been meaning to do god rays for ages and while doing the ST Excalibur post processing framework in SlimDX, thought I would give them a go.
This clip is of my XNA engine, I still have an issue or two with the render in SlimDX, but I am sure, once I have time, I'll write up an XNA blog post about how I did this and the references I used.
Sorry the clip is a bit messy, and forgive my jerky camera work, hope you like how it looks.