[Bf-vfx] Footage for Tracking

Wed Jun 8 22:44:05 CEST 2011

>
> Regarding file formats: JPEG frames are probably fine; there's little value
> in tracking on 16-bit data. The frames can even get converted to grayscale,
> since the tracking ignores color information.

are you not planning on using all the depth on the image for tracking ? in
my experience, it can helps a lot sometimes !

2011/6/8 Keir Mierle <mierle at gmail.com>

> On Wed, Jun 8, 2011 at 11:53 AM, Colin Levy <colin at peerlessproductions.com
> > wrote:
>
>> Yeah, rolling shutter is an *incredible* pain.  It can be corrected to an
>> extent with tools like The Foundry's "RollingShutter" plugin for Nuke, which
>> I've heard can make previously un-trackable shots trackable, but you see it
>> *everywhere* these days -- even in hollywood features.
>>
>
> Yes, we will deal with it but it will take some time. It's mathematically
> impossible to fix perfectly, so the best we can do is approximate fixes.
> Truly unfortunate.
>
>
>> I do have some footage I can get you from my Canon XH-A1, which is a 3-CCD
>> HDV camera.  I sold the camera recently (CMOS is all the rage!), but I have
>> a ton of footage I can go through.
>>
>
> That would be great! The only constraint is going to be calibration. Can
> you get access to the camera for 10 minutes to take some shots of a
> calibration pattern?
>
> I realize the big tools deal with this automatically, but it's difficult to
> do automatically and won't be supported in our first release.
>
>
>> That said, RED's CMOS sensor is waayy better than the "jellocam" sensors
>> in DSLRs like the 5D or T2i.  (RED's new MX sensor I think is even better).
>>  So the rolling shutter is not bad -- but it's still noticeable in very
>> high-motion shots.
>>
>> I'd say 80% of the RED shots I've got should not pose issues due to
>> rolling shutter.  The tracking tools I've been using do not account for
>> rolling shutter, yet I'm able to get very solid tracks with little manual
>> intervention.  So perhaps still valuable to test with?
>>
>
> Sounds like the RED shots will work as long as the motion is not too
> extreme.
>
> Regarding file formats: JPEG frames are probably fine; there's little value
> in tracking on 16-bit data. The frames can even get converted to grayscale,
> since the tracking ignores color information.
>
> Keir
>
>
>> --Colin
>>
>>
>> On Jun 8, 2011, at 2:32 PM, 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
>>>>>
>>>>> _______________________________________________
>>>>> Bf-vfx mailing list
>>>>> Bf-vfx at blender.org
>>>>> http://lists.blender.org/mailman/listinfo/bf-vfx
>>>>>
>>>>>
>>>>
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>>>
>>>
>>> --
>>> ____________________
>>> François Tarlier
>>> www.francois-tarlier.com
>>> www.linkedin.com/in/francoistarlier
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>>>
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-- 
____________________
François Tarlier
www.francois-tarlier.com
www.linkedin.com/in/francoistarlier
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