HI Elad,
I think you’re on the right track. I would shoot the girl greenscreen.
Depending on the look you want there are a number of ways to create the sand dune, everything from creating a sand dune miniature set to using foreground, mid and background photo elements to create your dune. You could build the dune environment as a series of 3D layers.
You might want to consider some of the warp plug-ins that come with AE in order to make it look like she’s being sucked into a hole smaller than she is. There are also numerous 3rd party effects you could use for this, but there are many in AE. I agree, you should combine this effect with blur.
You might want to try particle effects for your sand/dust. I really like Trapcode’s Particular (a 3rd party plug-in), but you could do it with Particle Playground or one of the other particle systems included with AE. There are some good tutorials on particle systems on Creative Cow. I also use a stand-alone product called Partical Illusion for effects like this. It has advantages and disadvantages in comparison to the partical effects plug-ins I mentioned, but could definitely work for this project.
If you run into problems or need some thoughts for setting up your green screen shoot, please feel free to send me an e-mail:
eric@giraffefilm.com
Best of luck,
Eric
Eric Goldstein
Giraffe Film Company
Los Angeles
eric@giraffefilm.com