Planar vector tracker 0.5.0 for Nuke

I want to share a gizmo that I have put together, that uses motion vectors
to track the pixel flow of the image. It is similar to what mokey and mocha
does, or what Furnace's motion match should do, although I usually don't get
good results with it.


The gizmo is good for tracking deforming surfaces which are hard to track
with a regular tracker. As a general rule, if the motion of the object can
be described with a planar deformation, the tracker will do a good job. You
need something to generate the motion vectors first, I use the furnace
motion vector generator (other software, like pftrack, might have other
formats, so you will have to massage the date to convert it to a similar
format to what the furnace plugin does - 4 channels, the first two describe
the pixel movement of the previous frame in float data, the other two of the
following frame in float data).

To use it, copy the vectors into the motion channels (forward vectors for
forward tracking,backwards vectors for backwards tracking) and plugin into
the gizmo.I am sharing this here because it has a lot of usability problems,
as I have found some limitations which I cannot solve, mainly with the
nuke.sample() calls, and would like to ask for your help to improve it.
 The current limitation is that in order to force the reload of the image so
that it is correctly evaluated by nuke.sample(), i have to render a temporal
file (you'll have to modify this temporal directory in order for the gizmo
to work in windows or mac, by replacing "/tmp/" in the gizmo source code
with the correct directory). This has as a side consequence that the viewer
does not update while tracking, and that you cannot cancel the track. If I
dont do this the viewer doesnt update fast enough and the tracker lags
behind, as the nuke.sample() is evaluated incorrectly.

It works, however. The vector generator that I use is the Furnace vector
generator, and the best setting that I have found for it are Vector Detail
1, smoothness .5, oversmooth activated, and block size 10. I usually render
it out as an exr into the main rgba file and plug it into the planar track.
The initial frame established is like a reference frame that is set on the
first frame that you track on. This means that you can offset the tracker if
the object goes out, is occluded, etc.

Please let me know if it works for you, or suggestions on how to improve it.
Thanks!

*This only works in 5.1!