[Bf-vfx] Footage for Tracking

[Keir Mierle]

A catalog of the following shots would be useful:

   - General motion: Moving and rotating camera. Camera is /not/ always
   pointing at one part of the scene.
   - Rotation only: camera on a tripod, rotating around a fixed point (if
   possible the camera's "Nodal point", but you need a special tripod for that)
   - Translation only: walking sideways keeping the camera pointed forward
   (e.g. not circling)
   - Translation only: walking towards the scene
   - General motion when the scene is planar (e.g. camera keeps a big
   billboard in view and only the billboard)
   - Circle strafing around an object; camera is fixated on one part of the
   scene (intersecting principal ray)

The scenes should have good texture so that tracking is easy; we can add
challenging scenes later. It's ok if the translation-only scenes have some
hand held wobble; that's fine. Boxes with texture are good. Complicated
objects like bushes or trees are bad. The scene must be static (no cars,
people, birds, godzilla, etc).

The camera must be calibrated. There is a libmv calibration target that you
can affix to a really flat object. The calibration target must be really
flat; something that has a bit of bend is unacceptable and will give poor
results.

http://libmv.googlecode.com/svn/trunk/extras/calibration/calibration.pdf

Take several images of the calibration target (or a video in HD). Get
different rotations and fill the frame to get the edges (important for
distortion correction). Then run one of the calibration tools to find the
intrinsic parameters (focal length in pixels, distortion, skew, etc).

Note: Rolling shutter is *horrible* for tracking. We're going to have to
handle it at some point, but I am trying to avoid it as long as possible. Do
you have access to a CCD style camera without a rolling shutter?

Keir

On Tue, Jun 7, 2011 at 3:27 PM, Ian Hubert <ian at projectlondonmovie.com>wrote:

> Hey all!
>
> I've been following the conversations, and wanted to throw out that if
> anyone needs any sort of footage, I can run out and film stuff. I already
> have a few things things filmed- mostly just walking around the city holding
> the camera as steady as I can- but if anyone wants anything else
> (underexposed, really shaky, steady smooth, panning--but-no-movement,
> somebody walking across the frame, stuff like that), just say so!
>
> At this point all I can quickly provide is SD and HD- I unfortunately don't
> have access to a 4k camera, but I'll film some random stuff if I ever get my
> hands on one.
>
> --
> Ian Hubert
>
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