3D Trajectories from a Single Viewpoint using Shadows
Ian D. Reid, Anthony C.T. North · 1998
We consider the problem of obtaining the 3D trajectory of a ball from a sequence of images taken with a camera which is possibly rotating and zooming (but not translating). Techniques are developed to compute the component of image motion of the ball due to camera rotation and zoom, using optic flow. The 3D location of the ball in each frame of the sequence is then determined using a novel geometric construction which makes use of shadows on the known ground plane in order to compute the vertical projection of the ball onto the ground, and the height of the ball above the ground. 1 Introduction In the absence of any other constraints, the image projections of world points in a single view of a scene are insufficient to compute a 3D reconstruction of the scene. The most obvious way to obtain 3D structure is therefore to consider multiple views separated spatially (and possibly temporally). An alternative to using multiple viewpoints is to enforce physical and geometric constrai...