[Bf-vfx] Blender camera tracking approach

[Remo Pini]

Hm... I have never noticed the slight distortions to cause issues with
the tracker... might be a question of the implementation, but I don't
see, why the material would have to be converted twice, even IF
"undistorting" is required...

(1) take original footage
(2) undistort to track (temporary copy)
(3) track
(4) distort tracking data according to undistort
(5) use original footage + track data + lensinfo from source (or
undistort function)

Syntheyes seems to do that under the hood, I guess, never seen tracking
issues due to distortions...


> -----Original Message-----
> From: bf-vfx-bounces at blender.org [mailto:bf-vfx-bounces at blender.org]
> On Behalf Of Tom M
> Sent: Sonntag, 8. Mai 2011 8:20
> To: Blender motion tracking & VFX
> Subject: Re: [Bf-vfx] Blender camera tracking approach
> 
> On Sun, May 8, 2011 at 10:06 AM, Remo Pini <remo.pini at avexys.com>
> wrote:
> > I kind of disagree...
> >
> > If you have lens distortion in you footage, this would most likely
be
> > bad and you would not want the final result to have that in it
anymore,
> > sooo....
> 
> You are thinking extreme distortion - this is about the very slight
> distortion that comes from all camera lenses due to their lense shape
> (as well as lense imperfections - but the imperfections are mostly
> ignored by most lense solvers).
> 
> Our brains ignore the distortion but it confuses trackers since travel
> in a straight line isn't straight with the distortion.
> 
> Undistorting the lense reduces the image quality because it shifts
> pixel locations and thus 'blurs' pixels that the undistorted location
> of a pixel will not be exactly on the pixel boundary of a previous
> pixel.
> 
> Thus undistortion is only used to provide straighter lines to the
tracker.
> 
> Applying the lens distortion to your rendered image is so that it's
> straight lines are curved similarly to that of the original image.
> Again this introduces blurring of your render if it is applied as a
> post process - so either you need to render larger or do the
> distortion at render time.  In practice the amount of bluring from
> doing it as a post process is probably not significant enough to be
> noticable in most situations.
> 
> LetterRip
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