Levitation Effect

[wcthrill]

Not sure if this is the right topic to post but here goes. Im trying to create a sfx where I film someone is sitting on a couch and then have the person slowly levitate. Any ideas on how to do this. Do I need a green screen? Or do stop motion flilming?

[guns1inger]

There are a number of ways to do it, depending on the software you have available.


Method One - Keying

You could do it with a green screen type effect. Fix the camera on a tripod and film the empty couch. Next, cover the couch with green or blue sheet, making sure it also goes some way up the wall behind it. Film the person sitting on the couch while the sheet is in place. Make sure you have good, even lighting and some back light as well.

You should now be able key out all the couch and wall behind the person, and overlay this on to the shot of the empty couch. Depending on the software used, you may also have to create masks or garbage mattes for ares not covered by the couch. By moving this overlay up and down in the frame, the person will levitate.

Method Two - Masks

Similar to method one, but minus the sheet. Again, with a fixed tripod, film the empty couch. Film it a second time with someone sitting on it. Using something like after effects or combustion, you can now create a mask around the person on the couch to isolate them and move them independently. By having a shot of the empty couch underneathm as they move up, the transparent areas left behind will be filled by the empty couch.

Method Three - Stills

Take a photo of the empty couch using a fixed tripod. Take a second photo of the person sitting on the couch. In photoshop or similar, remove the background around the person and save the image as a tga file with alpha mask representing the missing space around them. Load the two stills into your editor, with the tga as the overlay, and move it up and down to complete the effect.

Method One and Two are complex, but allow for the person to move around. With a green screen this isn't too much of an issue, but if you are hand masking it can be time consuming.

Method Three is the simplest, but may look more like a Terry Gilliam animation.

[gadgetguy]

The hard part about the first two methods is that a normal couch with cushions will look different when someone is sitting in it than when not. To get true realism you would have to devise a way to film the couch with the cushion depressed and then have it decompress as the subject "levitates". One way of doing this is to use a large button and 200lb fish line and a pulley. Mount the pulley under the couch below the center of the cushion. Run the fish line down through the cushion, through the base of the couch, through the pulley and out the back of the couch. Have someone behind the couch pull on the line to compress the cushion then while you're filming have them slowly release the line.

[guns1inger]

If you are going to get that fussy, get ILM to do the whole thing in CGI for you

[gadgetguy]

If a thing is worth doing...