Volumetric light

does anyone have an Idea how to make volumetric light shafts
that react to overlay pictures (such as leaves on a tree)

The reason is that I am making a deep jungle scene
(a lot like the videos of crisis Ive seen on youtube)

the sun is almost directly overhead.

If you already know how I could really use some help.
Or if you just want to post ideas on how to pull this off that could help to.

even when someone explains it to you you would need the shader knowledge to implement it or the money to pay one who is able to do that for you....
graphics are the second thing you have to think about
-develop a playable game first

well he didnt say whether he's making a gameplay or just a scene, i remember two of them, one is from shadeC by BoH_Havoc, should be quite easy to find with a search, the other am not so sure where its from but searching and you may find it

dont forget that there is a difference between real volumetric light and pp-light shafts like this: http://hummel.slindev.com/bilder/LightShaftsDemo.png

Am I correct in assuming that the fake pp-light shafts require less power than real volumetric light.

If you have any usefull references I could look up, that would be great.

to me either one works, and I do have slight knowledge in shader programming.

slin is currently trying to convert on of my HLSL funcs to Lite-C once he is ready I´ll upload the light-shafts demo

Maybe using volume shadow used in stencil shadow, but change it to white instead of black. Dunno if this applicable since shadow volume was handled inside the engine or has anyone tried that?