We have developed a technique for determining ground truth motion fields in real scenes. In a scene consisting of polygonal objects we draw polygons which match the visible faces of the objects over a sequence of images. By determining which polygon a given pixel lies in we can calculate a motion vector using a perspective transform from the polygon in the current image to the corresponding polygon in the next image.

We have developed a Tcl/Tk tool  which implements this technique. The tool is used to draw the polygons on each frame of the image sequence and can then output the optical flow as PCM files. The PolyFlow tool is available for download here.

The diagram below shows how the PolyFlow tool is used. Once the image sequence is loaded, polygons are drawn in each frame. Here the blue polygon represents a polygon in the background plane (as defined by the green dots in the sequence) and the red polygons define the faces of the box. The polygons are then used to calculate motion fields which are outputted as PCM files.
 
 

Image #1 Image #2

PolyFlow

Calculate Motion Field