2005General Discussion forum
Motion tracking of steadicam footage for integration with motion-controlled models in large-scale green screen productions
21 years old. Gear and prices may have changed since.
What the thread found
- Multiple motion tracking approaches exist for steadicam work, including software-based tracking from footage and external hardware-based tracking systems.
- Boujou (versions Bullet and Three) can analyze footage to extract 3D camera movement data for export to motion control systems by tracking marked reference points.
- Placing tracking markers such as white balls or tennis balls on green screen walls and hanging them from ceiling on chains provides reference data for motion tracking software.
- Multiple small cameras mounted on the steadicam rig itself, positioned 12 inches apart or more, enable stereoscopic tracking that improves accuracy compared to single-camera tracking.
- External infrared LED and infrared camera systems, sometimes called antler rigs with tracking balls, can track steadicam movement in real-time but have spatial coverage limitations.
- The tracking camera or cameras should use the widest available lens to capture maximum environmental data for accurate motion reconstruction.
- Tracking footage should include extended movement before the shot start and after the shot end to provide the tracking software with more environmental reference information.
- Building a custom rig with ping pong balls at multiple points and recording from multiple mini-DV camera angles allows manual 3D reconstruction of camera movement through 3D modeling software.
- Systems like the Thoma Walkfinder use LED balls and infrared ceiling cameras but have significant height and space coverage limitations that may not suit large studio dimensions.
Depends on
- Hardware-based tracking systems have maximum spatial coverage limitations, typically around 250 square meters, making them unsuitable for very large sets.
- The accuracy of ping pong ball tracking decreases at distance with wide-angle lenses as the markers become too small to track reliably.
- Some participants noted technical feasibility questions remained untested or unresolved regarding specific implementations.
- Interlaced video can be used for tracking but progressive scan video is preferable.
- The discussion occurred in 2005 with recommendations about specific camera models that may be outdated.