[Bf-vfx] Footage for Tracking

Wed Jun 8 23:17:29 CEST 2011

On Wed, Jun 8, 2011 at 1:44 PM, François T. <francoistarlier at gmail.com>wrote:

> 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 !

Maybe eventually but not to start. Libmv takes 32 bit grayscale float images
to track them. However, I'm skeptical that more than 8 bits of grayscale
data would make a difference for tracking. Do you have examples where this
is the case?

Keir

> 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
>>>>>>
>>>>>>
>>>>>
>>>>> _______________________________________________
>>>>> Bf-vfx mailing list
>>>>> Bf-vfx at blender.org
>>>>> http://lists.blender.org/mailman/listinfo/bf-vfx
>>>>>
>>>>>
>>>>
>>>>
>>>> --
>>>> ____________________
>>>> François Tarlier
>>>> www.francois-tarlier.com
>>>> www.linkedin.com/in/francoistarlier
>>>>  _______________________________________________
>>>> Bf-vfx mailing list
>>>> Bf-vfx at blender.org
>>>> http://lists.blender.org/mailman/listinfo/bf-vfx
>>>>
>>>>
>>>>
>>>> _______________________________________________
>>>> Bf-vfx mailing list
>>>> Bf-vfx at blender.org
>>>> http://lists.blender.org/mailman/listinfo/bf-vfx
>>>>
>>>>
>>> _______________________________________________
>>> Bf-vfx mailing list
>>> Bf-vfx at blender.org
>>> http://lists.blender.org/mailman/listinfo/bf-vfx
>>>
>>>
>>>
>>> _______________________________________________
>>> Bf-vfx mailing list
>>> Bf-vfx at blender.org
>>> http://lists.blender.org/mailman/listinfo/bf-vfx
>>>
>>>
>>
>> _______________________________________________
>> Bf-vfx mailing list
>> Bf-vfx at blender.org
>> http://lists.blender.org/mailman/listinfo/bf-vfx
>>
>>
>
>
> --
> ____________________
> François Tarlier
> www.francois-tarlier.com
> www.linkedin.com/in/francoistarlier
>
> _______________________________________________
> Bf-vfx mailing list
> Bf-vfx at blender.org
> http://lists.blender.org/mailman/listinfo/bf-vfx
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.blender.org/pipermail/bf-vfx/attachments/20110608/d08dbdf5/attachment.htm 