Monday, March 17, 2008

Pinocchio's Nose

under construction

Pinocchio’s Nose

Overlaying a flying airplane image onto any video is easy. Videos are composited in layers. The flying airplane layer is prepared in advance. The airplane could be originally drawn on computer, or actual video of a real aircraft. Either way, the background is removed and the plane image sits on an otherwise transparent layer. Placing this layer on top of a second layer will make the plane appear to fly in front of everything else.

Making the plane appear to disappear behind the edge of a building requires adding a third layer, and using what’s called a “layer mask”. A layer mask defines areas of the screen where everything on that particular layer disappears. One way to create a mask is to draw a shape. Anything which goes inside the shape disappears. But compositing software can also create masks in real time based on differences in color and brightness. In Chopper 5, a mask was created to determine what was and was not “sky”.

Here, in Final Cut Pro, I’ve used luminance (brightness) to create a mask on video of the twin towers. Once correctly dialed in, the software has no difficulty distinguishing between the sky and everything else. We now have a total of 3 layers: The top layer is the towers with transparency instead of sky, the middle layer is the plane, and the bottom layer is the original video of the twin towers. Then all that needs to be done is to play the airplane layer. The plane crosses the sky, and disappears behind the tower.

Adding the plane and disappearing it inside the layer mask is easy. Trickier is to stop playing the airplane layer at the correct time. Stop it too soon, and the plane freezes or disappears in mid air. Stop it a little too late, and it will appear to slip out from the back side of the mask.

Unfortunately for the creators of Chopper 5, this is what happened. The airplane layer was played a little too long, and the nose of the airplane appeared to pop out from behind the tower. This has become known as “Pinocchio’s Nose” or “The Nose-Out”.

It is impossible that the nose cone of a real Boeing 767 could survive and pop out the back of the tower. It is hollow, made of plastic, and not designed to withstand any sort of impact. Plus, there is no “exit wound” on the tower where such an event would have occurred. Obviously the plane image was accidentally allowed to come out from behind the layer mask. The only alternative explanation is that what appears to be the nose of the plane is actually some sort of “dust explosion”. Yet the “dust explosion” is indistinguishable from the nose of the airplane.

Here are 6 cropped images, 3 are the nose of the airplane from before it appeared to enter the tower, 3 are from the nose-out event. 

Can you tell which are which? How would it be possible that a dust explosion could become a size, shape and color that are indistinguishable from the nose of the very airplane that just crashed on the other side of the building?

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