I need to create a scene where a girl is standing on a dune and being sucked into the sand.
I thought about greenscreening the girl and then move her into the ground, using masks to achieve the look of her being sucked, adding severe motion blur and sand particles.
I'm not quite sure how to shoot and achieve this effect.
Any advice would be appreciated.
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:
Best of luck,
Giraffe Film Company