[Bf-vfx] Non-square shapes for pattern and search areas

[Nathaniel Watson]

+1 to what Matt and Francois have said; having rectangular trackers is very
useful in some specific cases - here's a screenshot of the first example I
could find: http://dl.dropbox.com/u/1470205/123531.png
<http://dl.dropbox.com/u/1470205/123531.png> (it's
not very clear - sorry!)
Having the tracker as a smaller square would mean the pattern wouldn't be as
unique, so the tracker would probably slide to the similar areas at the
right, while making it a larger square would make the pattern grab the
foreground area (it's hard to see, but the foreground is on the left of the
image, separated by a diagonal line), also resulting in sliding, or a
shorter-lived tracker.

-Nathaniel

On 21 July 2011 20:54, François T. <francoistarlier at gmail.com> wrote:

> @julien : they can be useful in some cases yes, especially for 2.5D
> tracking, corner pin, Roto,.... check out what people do with it (
> http://www.imagineersystems.com) To be honest, it wouldnt be my priority
> at least for matchmoe, but it is a very powerful tool, so at some point if
> you guys feel like it sure why not ;-)
> I personaly use it for all corner pin stuff. (The tutorial Sebastian did ?
> it's 10 times easier and faster with planar tracking) and for removal object
> as well, but not for matchmove purposes
>
> @Keir : found an example just right now of a case where I add to use
> rectangular pattern w/o any chance to do otherwise *(Of course I cannot
> share the footage with you, so you'll have to trust me on that one, or make
> the test yourself :) )*
> LED + motion blur. They used LED as markers on set. With motion blur the
> LED becomes a strip but for a start the pattern has to be as small as the
> LED otherwise you will get jittering. but when you get motion blur, the LED
> gets wider and the pattern needs to stay at the center of this strip be
> correct, so if the pattern is not wider than the blur LED, the marker will
> drift. And if you keep it square it might become a big pattern where the LED
> brightness is so little compare to the all rest, that the tracker won't care
> too much about LED anymore but mostly about what does surround it, which
> result also as drift
>
> hope you got it :p
>
> cheers
> F.
>
> 2011/7/21 julien michot <julien.michot.fr at gmail.com>
>
>> This is not *yet* a planar tracker!
>>
>> What do you think about planar trackers, are they more efficient or easier
>> to use?
>> Would it be useful to implement one in libmv?
>>
>> -julien
>>
>>
>> On Wed, Jul 20, 2011 at 10:28 PM, François T. <francoistarlier at gmail.com>wrote:
>>
>>> I don't know why you would need that. This is not planar tracking, so it
>>> really doesn't matter at the end.
>>>
>>> F.
>>>
>>> 2011/7/20 Sergey I. Sharybin <g.ulairi at gmail.com>
>>>
>>>>  Hi everyone!
>>>>
>>>> It was got discussion today in #lbmv at irc.freenode.net related on
>>>> forcing pattern/search area be square.
>>>>
>>>> Main question: is non-square shape of marker useful in motion tracking
>>>> workflow?
>>>>
>>>> Some quick cases i could think could be solved just adding offset to
>>>> search area or by resizing this areas.  But we've checked some tracking
>>>> applications and they allow to use non-square markers. So i'm not sure
>>>> it'll be good idea to stick to squares.
>>>>
>>>> P.S. From UI point of view, search are could be rectangular, just
>>>> "missing" areas could be filled with black when it's passing to libmv which
>>>> would probably be optimized for squares.
>>>>
>>>> --
>>>> With best regards, Sergey I. Sharybin
>>>>
>>>>
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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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