When in Dome…

The Morehead Planetarium & Science Center Production Blog

Live Action for dome’s sake.

by Peter Althoff

August 3, 2009 | No comments | Production, When in Dome

I’m going to discuss some potential issues I’ve been mulling over about blending live action and cg on a dome. Following links will discuss in further detail some of the terms I may be using.
Chroma Keys (Aka, Green Screen)
Match Moving

Generating live action footage for a dome has been an on going challenge for anyone producing content larger than 2k. The current resolution standards on most HD cameras only allow us to create the bottom have of a 4k fisheye master. This means of course that part, if not all, of the environment that live actors interact with will need to be computer generated. Also shooting live action, you’re somewhat limited to how much motion you can incorporate into a shot.

The challenge of shooting a moving camera shot, is needing to match that motion in the digital 3d world. You’ll need to be able to record the camera’s position and orientation for each camera move, and replicate it so that your filmed and separated actor/actors are rooted to the scene. You could achieve this using a motion control rig that the camera sits on. With every take you can program the camera’s move so that human error is removed from the situation. The downside is the cost of renting and operating such equipment can be excessive.

Another option is to try syncing the camera up using some match move software and tracking markers. Though most of the software has been developed to track xyz positions in relation to a single plane of footage, and has yet to be calibrated for working with the unique distortion of a fish-eye lens. A work around would be to lock down the camera during filming and then move the actors image in 3d, but would be limiting in its ability to recreate complex camera moves.

Hopefully as Fulldome video becomes more mainstream, camera companies will develop the hardware that will make live action a more plausible solution for smaller studios. The benefits of using real actors, and building on existing sets, leads to a more believable experience for audiences. It also makes production a little simpler because practical solutions can be generated rather than leaning everything on being created in post.

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