Add a new hybrid region tracker for motion tracking to libmv, and

add it as an option (under "Hybrid") in the tracking settings. The
region tracker is a combination of brute force tracking for coarse
alignment, then refinement with the ESM/KLT algorithm already in
libmv that gives excellent subpixel precision (typically 1/50'th
of a pixel)

This also adds a new "brute force" region tracker which does a
brute force search through every pixel position in the destination
for the pattern in the first frame. It leverages SSE if available,
similar to the SAD tracker, to do this quickly. Currently it does
some unnecessary conversions to/from floating point that will get
fixed later.

The hybrid tracker glues the two trackers (brute & ESM) together
to get an overall better tracker. The algorithm is simple:

1. Track from frame 1 to frame 2 with the brute force tracker.
   This tries every possible pixel position for the pattern from
   frame 1 in frame 2. The position with the smallest
   sum-of-absolute-differences is chosen. By definition, this
   position is only accurate up to 1 pixel or so.
2. Using the result from 1, initialize a track with ESM. This does
   a least-squares fit with subpixel precision.
3. If the ESM shift was more than 2 pixels, report failure.
4. If the ESM track shifted less than 2 pixels, then the track is
   good and we're done. The rationale here is that if the
   refinement stage shifts more than 1 pixel, then the brute force
   result likely found some random position that's not a good fit.

1 files changed, 1 insertions, 0 deletions

diff --git a/source/blender/makesrna/intern/rna_tracking.c b/source/blender/makesrna/intern/rna_tracking.c
index 89c17819265..5a2ef54cfc1 100644
--- a/source/blender/makesrna/intern/rna_tracking.c
+++ b/source/blender/makesrna/intern/rna_tracking.c
@@ -269,6 +269,7 @@ static MovieTrackingMarker *rna_trackingTrack_marker_find_frame(MovieTrackingTra
 static EnumPropertyItem tracker_items[] = {
 	{TRACKER_KLT, "KLT", 0, "KLT", "Kanade–Lucas–Tomasi tracker which works with most of video clips, a bit slower than SAD"},
 	{TRACKER_SAD, "SAD", 0, "SAD", "Sum of Absolute Differences tracker which can be used when KLT tracker fails"},
+	{TRACKER_HYBRID, "Hybrid", 0, "Hybrid", "A hybrid tracker that uses SAD for rough tracking, KLT for refinement."},
 	{0, NULL, 0, NULL, NULL}};
 
 static EnumPropertyItem pattern_match_items[] = {