Blender Git Loki

Support for per-track Grease Pencil datablocks for motion tracking

Originally was needed to reach easy way of defining masks used for tracking
(do eliminate textures which doesn't belong to feature when tracking.

Implemented as alternative to GP datablock for clip and added switch between
per-clip and per-track GP datablocks -- internal limitations of GP doesn't
allow to display all GP datablocks easily. So either you see.edit GP associated
with clip or with track.

GP strokes associated with track are relative to track's position, following
tracks during tracking and could be shared between several tracks.

Masking code presents in libmv and there's rasterizer of GP datablocks for
masks in blender's tracking module, but they still need to be glued together.

Some documentation cound be found at this page:

http://wiki.blender.org/index.php/Dev:Ref/Release_Notes/2.64/Motion_Tracker#Grease_Pencil