Compositor: Expose track velocity via the Track Position node

velocity is measured in pixels per frame. It is basically a coordinate
difference of track coordinate at current frame and previous one (no future
prediction happens).

It's not really most intuitive place for such a things, but historically the
node was called this way..

Track velocity could be used to face effects like motion blur bu piping it
to the vector blur node.

Reviewers: campbellbarton

Reviewed By: campbellbarton

Subscribers: hype, sebastian_k

Differential Revision: https://developer.blender.org/D1591

2 files changed, 13 insertions, 1 deletions

diff --git a/source/blender/compositor/operations/COM_TrackPositionOperation.cpp b/source/blender/compositor/operations/COM_TrackPositionOperation.cpp
index ca169d03fbc..52ceb50e693 100644
--- a/source/blender/compositor/operations/COM_TrackPositionOperation.cpp
+++ b/source/blender/compositor/operations/COM_TrackPositionOperation.cpp
@@ -45,6 +45,7 @@ TrackPositionOperation::TrackPositionOperation() : NodeOperation()
 	this->m_axis = 0;
 	this->m_position = CMP_TRACKPOS_ABSOLUTE;
 	this->m_relativeFrame = 0;
+	this->m_speed_output = false;
 }
 
 void TrackPositionOperation::initExecution()
@@ -78,7 +79,16 @@ void TrackPositionOperation::initExecution()
 
 			copy_v2_v2(this->m_markerPos, marker->pos);
 
-			if (this->m_position == CMP_TRACKPOS_RELATIVE_START) {
+			if (this->m_speed_output) {
+				marker = BKE_tracking_marker_get(track, clip_framenr - 1);
+				if ((marker->flag & MARKER_DISABLED) == 0) {
+					copy_v2_v2(this->m_relativePos, marker->pos);
+				}
+				else {
+					copy_v2_v2(this->m_relativePos, this->m_markerPos);
+				}
+			}
+			else if (this->m_position == CMP_TRACKPOS_RELATIVE_START) {
 				int i;
 
 				for (i = 0; i < track->markersnr; i++) {
diff --git a/source/blender/compositor/operations/COM_TrackPositionOperation.h b/source/blender/compositor/operations/COM_TrackPositionOperation.h
index 10dbaf96646..a5a58ad9f09 100644
--- a/source/blender/compositor/operations/COM_TrackPositionOperation.h
+++ b/source/blender/compositor/operations/COM_TrackPositionOperation.h
@@ -47,6 +47,7 @@ protected:
 	int m_axis;
 	int m_position;
 	int m_relativeFrame;
+	bool m_speed_output;
 
 	int m_width, m_height;
 	float m_markerPos[2];
@@ -67,6 +68,7 @@ public:
 	void setAxis(int value) {this->m_axis = value;}
 	void setPosition(int value) {this->m_position = value;}
 	void setRelativeFrame(int value) {this->m_relativeFrame = value;}
+	void setSpeedOutput(bool speed_output) {this->m_speed_output = speed_output;};
 
 	void initExecution();