[Bf-vfx] Footage for Tracking
ibkanat
ibkanat at gmail.com
Wed Jun 8 20:50:24 CEST 2011
Didnt Julian or someone add a fix to rolling shutter to libmv recently?
I also found a interesting paper that was in siggraph two years
ago(http://pages.cs.wisc.edu/~fliu/project/3dstab.htm)
On Wed, 2011-06-08 at 11:32 -0700, Keir Mierle wrote:
> Thanks Colin!
>
>
> One point though: RED uses a CMOS sensor and is subject to rolling
> shutter. Do you know how bad it is? Some cameras have very slow sensor
> readout (and so terrible distortions with movement) and others have a
> faster rolling shutter which still has distortions, but less.
>
>
> For those who don't know: rolling shutter means that each scanline has
> a *different* shutter time! Yes, that means that the image is composed
> of 1000's of images, one scanline taken from each, with the camera
> moved between images. Extremely annoying, and totally breaks all the
> camera tracking assumptions.
>
>
> I realize that we have to handle rolling shutter but it's a big job
> and we won't support it in the first release.
>
>
> So I repeat my request: does anyone have a camera that doesn't have a
> rolling shutter? For example, the Panasonic SD9 has a CCD sensor and
> so takes true pinhole images for each frame.
>
>
> Virtually all modern DSLR's have awful rolling shutter (D90 included),
> so they are also excluded.
>
>
> Keir
>
> On Wed, Jun 8, 2011 at 11:00 AM, Colin Levy
> <colin at peerlessproductions.com> wrote:
> Hey guys,
>
>
> I've got several TB worth of 4K material I can offer for
> tracking. However, the shots will represent a more
> "real-world" scenario rather than the test case shots listed
> below.
>
>
> I don't suppose you want the RED .r3d files, so will TIFF
> sequences work for you? (Or do you want both?) I will go
> through my drives in the next few days and upload a few shots
> to my FTP, if you think this would be useful! Let me know
> whether you'd like 32-bit images, with all the 'RAW' data
> intact, or if 8 or 16bit will suffice.
>
>
> One thing to note regarding resolution: I have noticed that in
> many cases, tracking downrezzed shots is frequently more
> successful than trying to track the raw 4K material. This may
> have something to do with the default values (the default auto
> feature search range, for example, may be something like 20px
> rather than 80px, which might be a better setting for 4K).
> For my projects I usually downrez to 2K before tracking...
> also because it's a lot faster. :P
>
>
> Great discussion. Can't wait to see these tools develop!
>
>
> --Colin
>
>
>
>
>
> On Jun 8, 2011, at 12:59 PM, François T. wrote:
>
> > I'll do all that on saturday with D90.
> >
> >
> > cheers
> > F.
> >
> > 2011/6/8 Keir Mierle <mierle at gmail.com>
> > 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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> >
> >
> >
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> >
> >
> >
> > --
> > ____________________
> > François Tarlier
> > www.francois-tarlier.com
> > www.linkedin.com/in/francoistarlier
> >
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>
>
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