[Bf-committers] suggestions for the tracking tools

Sergey Sharybin sergey.vfx at gmail.com
Wed Sep 3 13:00:54 CEST 2014


Some answers are inlined.

1- The trackers should be displayed in the Graph editor. It's useful when
> you have long shots tracked and you want to smooth some parts. Also useful
> to detect shakes in the camera.

Tracks are using own "animation" -- in fact, track si just a set of
markers. It has quite specific usecase and operations allowed to do, which
doesn't fit into generic animation system for which Graph/Dopesheet editors
are designed for. For example, it doesn't make sense to be able to keyframe
tracks from the graph editor or to tweak keyframes from the dopesheet.

There's own graph "editor" (more like visualizer) for the motion tracking
tracks. If some functionality is missing there please let me know which one.

But as for manual "smoothing" of the tracks -- that's really a bad idea.
Instead of smoothing the track motion you should drop it. General rule here
-- motion tracking is expected to be rock-solid and point at exactly the
feature you're tracking. If it gives "jumps" on the curve -- it's either
bad feature to track (an you shouldn't use this track) or it's indeed how
the feature moves in the camera space and trying to smooth this out will
make camera solution less accurate.

> 2- Colour chooser with threshold. Apart of the very useful R,G and B
> channels it would be awesome to have a colour picker to choose exactly the
> colour we want to track in the pattern and that could be complemented with
> a threshold value. We use this feature intensively and makes extremely easy
> to track certain shots.

Motion tracking works in the grayscale space and don't take color into
account at all. Disabling R/G/B just gives some tips how to convert the
footage to the grayscale. We could try doing some difference key approach
here before converting the frame to grayscale, but i'm not really sure how
well it's gonna to meet your needs.

Do you have an examples when you feel doing tricks like this would help
tracking (.blend with footage is the best :)?

> 3- A graph showing how many trackers are "active" in each frame of the shot
> so we can easily know in which frames we should put more effort. In one
> axis we have the frames and in the other the number of active trackers.

This is done in the dopesheet view of the Clip Editor. It doesn't give you
exact number, but it tells you how good the frame coverage is.

What do we miss in there?

> 4-Maybe this one could be applicable to other areas of Blender. When we are
> going to use proxies we usually use other application to actually create
> the proxies. That application is using our render farm to do the job, so
> it's really fast. However in Blender we don't have the chance and it's damn
> slow. Also I suspect the proxy generation stuff is not even multi-threaded,
> is that right? So, a way to create the proxies in the render farm, if any,
> would be very welcome.

This is complicated. For the image sequences proxies are nicely
multi-threaded -- different frames are handled in different threads which
sohuld give the best threadability. For movies threading happens within a
single frame when dowscaling it. This gives more overhead, but still faster
than a single thread.

I need to know exact details of the input data (maybe you even have
shareable examples which we might use for benchmarking?) to answer the
question whether we can do a better job. How much nodes you've got in the
farm and how much threads you've got in CPU?

Also, you can easily generate proxies in the render farm and just switch
the movie clip filepath between the proxy and final footage. For as long
the frames matches (there's no frame shift) and they're the same aspect
ratio motion tracking would be just happy. Doesn't mean we wouldn't look
into trying to make proxies generation faster, but at least this could
solve your stoppers for now (unless you're not aware of this yet :)

> Is there a way to "deactivate" a tracker for an specific frame(or group of
> frames) so it's not evaluated during the solving?

Shift-D in the default keymap i believe. It toggles the "enabled" flag of
all selected tracks on the current frame.

> And also I would like to know if there is an specific place to talk about
> the tracking tools apart of this mailing list.

Better place for such a VFX-related topics is bf-vfx mainling list. You can
also drop to #blendercoders IRC room at irc.freenode.net if you want to
talk to developers. But for more like artist-specific/support/questions
things i'm not really sure about. Maybe Sebastian here could answer better
this question.

With best regards, Sergey Sharybin

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