The use of clean plates in wire removal is very common and gives good results in certain situations.
Consider a scene shot with an actor suspended from wires and then the same scene shot again without the actor. This second sequence is called the clean plate. The wires from the first shot can be painted out using pixels from the clean plate leaving the actor suspended in thin air.
Shooting a clean plate if the camera is locked off is easy. If the camera moves, then motion control rigs can be used to exactly reproduce the first pass. But it doesn’t always work, particularly if the scene is shot against backgrounds that don’t look the same on the second pass, such as clouds, sky, or smoke. Motion control rigs are also expensive and that makes them a rarity. Often, a clean plate is not shot during the filming and the compositor is left to create one by merging together unobstructed pixels from many frames. This single frame can then be tracked into place to cover the wires.
FurnaceCore’s wire removal plug-in should make the process of wire removal much easier. It is particularly good at removing wires over heavily motion blurred backgrounds or wires over smoke, dust, or clouds. It can be used to remove each wire in a sequence or to quickly create a clean plate which can then be tracked into place.
The reconstruction of the background behind the wire can be done spatially, in other words, using only information from the current frame. Alternatively, motion estimation techniques can be used to warp frames from before and after onto the current frame so that, where available, background pixels from these frames can be used to improve the repair. Our reconstruction methods are unique in that they remove the wire without removing and reapplying the grain. They are also tuned to remove long thin objects, leaving other objects untouched. For example, if transient foreground objects cover the wire, they will be left alone.