How to use a "Grid" to make a Background Plate mo

Ivan Speilberg · Post by **Ivan Speilberg** » Sat Nov 22, 2003 9:02 pm

I'm planning to shoot a fight in front of a blue screen. I'm using blue-painted wires to fly the actors. As they get hit, the camera moves backwards with them so that it will be less noticeable that I'm using Croma.

I remember having seen people place neon-orange balls (or tape) in their blue/green screens to create a grid, so that they can track the movement of the camera and animate the background plate to react REALISTICLY to it. I saw this technique in the behind-the-scenes of "Space Jam".

HOW THE HELL DO THEY DO THAT!!!! I really need to make this effect work for my college film NEXT MONTH!!!!!

o:(
ANY TUTORIALS OR LINKS ARE DESPERATEDLY WELCOMED!!!!!:(:(:D

insert_coin · Post by **insert_coin** » Sun Nov 23, 2003 4:28 pm

the balls can be placed in a pattern or randomly on the wall all they act as is a reference for camera tracking software... the camera tracking software tracks the balls or X's and using mathematics and the movement of the features its tracking it can estimate how the camera moves... its just to help the camera track because without them the tracking software has no information to track since the movement of actors must be masked and not taken into account otherwise the program will get confused. so the grid is only to provide tracking software with information it needs to track

Ivan Speilberg · Post by **Ivan Speilberg** » Sun Nov 23, 2003 5:16 pm

Thanks for the info Insert_Coin!!:D
I didn't knew that the balls may be scattered randomly, I Kinda' knew knew everything else:) but thanks anyways.

You are from the good ones, the ones that explain the concepts for the benefit of everyone else:D (That's good)

Do you, or anybody else know of how any tracking software ?? CAN IT BE DONE WITH After Effects????!!!

padawanNick · Post by **padawanNick** » Sun Nov 23, 2003 7:13 pm

The actual simulated camera movement is usually done with w 3D program like 3dMax.

There used to be a free program called Icarus that would calculate the proper camera animation, but that has gone commercial and sells for a few thousand dollars now. You may still find a copy somewhere on PTP networks or something.

There is a free program called Vodoo from the University of Hannover. You can download it from the official site.

Programs like Vodoo and Icarus calculate the camera motions and export a script for use in a 3D app to perform the camera moves.

Good luck.
Have fun.

insert_coin · Post by **insert_coin** » Sun Nov 23, 2003 8:19 pm

Hey Nick thanks for pointing out vodoo!
But since i stick to software that is good id suggest Icarus now untill i try this vodoo out. Ive still got 2.0something im not sure.. but if u want it i can maybe upload it to a secret location...

padawanNick · Post by **padawanNick** » Mon Nov 24, 2003 3:27 am

I'm all set, thanks. (I'm running Icarus v2.07)

... but there may be others here that have 3dMax that could use it.

Have fun.

insert_coin · Post by **insert_coin** » Mon Nov 24, 2003 9:16 am

perhaps that is true... however the voodoo website says it can only calculate pan/tilt/zoom shots. So that means you will need to shoot all your tracking shots on a tripod