The camera always lies...
Digital Stitchery in VFX
What is Digital Stitchery?
How did we use it?
The art of sewing two different shots together into one seamless take. There are a number of techniques, both simple and complex which can be employed in both editorial and VFX. This study demonstrates advanced compositing methods and examples.
Our challenge for the following examples was to create a seamless fight sequence comprising four individual parts, and to duplicate the same actor on screen twice without an apparent cut.
Let’s look at our first example: Whitechapel’s continuous fight sequence.
Whitechapel videos are password protected: WC4stitchery08
The director opted to use a track and dolly in order to keep the footage steady and f luid. The constraints of the equipment and location meant the sequence had to be split into sections to allow time to re-position the camera around the common action. The desired camera angles and movements were choreographed into four sections and a “10 minute test” was undertaken during prep to familiarise the team with the shooting process.
Here’s a specific shot in detail. Plate 1 shows the action up to the cut point. The camera swings down to track the actor rolling on the f loor, and sees him drop the weapon. This cut will be where plate 2 picks up.
Plate 2 shows the actor pick up the weapon and roll the other way. The pickup shot had an 180 degree movement and required a specialist camera head used solely for this plate.
This is a crude sequence to illustrate the difference between the camera position of the two plates.
This frame depicts the beginning of the paint and projection work needed to align the perspectives of the two plates and clean up the dissimilar areas. This was a timely process to create a consistent background.
This image shows the compositional split between the two plates. The red masked area is taken from plate 2 and the ground from plate 1.
The final composite, demonstrating how the two plates were blended.
You can see the compositional split highlighted in the image above. The red masked area is taken from plate 2 and the ground from plate 1.
This clip depicts a rough cut of the four hero shots. Look closely and you will see the unfinished seams.
All sections are sewn together in the composite to create the final sequence.
The camera always lies...
Digital Stitchery in VFX
Another example of how digital stitchery can be used is demonstrated in this clip from The FFades. For this particular shot the director wanted to create a shot that showed the same character twice in the scene: he would walk towards the door of a hospital room, and see himself through the glass lying in the bed. The camera would transition through the glass, move around the bed and finally see him standing at the door, looking at himself. Similarly to the Whitechapel example, the scene was broken up into three overlapping shots, creating an illusion of continuous action. It is also important to note that no motion control was used for the following shot. Digital stitchery allowed the sequence to be created using just a steadicam unit.
Plate 1 shows the actor walking towards the hospital room door. Behind the door we see a green screen, which will eventually be replaced with plates 2 and 3, once they have been digitally stitched together by the compositor.
Plate 2 shows inside the hospital room with the actor lying in the bed. The camera carefully recreates the same move as plate 1 to provide a background to replace the greenscreen. Once in the room the camera continued to move around the bed using the medical equipment to wipe into plate 3.
Plate 3 provides the end of the sequence. It was important to perform an identical move to that used in plate 2, paying special attention to the position of the medical equipment that was used a linear wipe. The shot continues around the room to finally pick up our actor looking at himself through the glass.
How does it actually work? Each individual section must start where the previous ended and end where the following begins, mimicking the same camera moves as its predecessor and successor. This allows the compositor enough material to blend together in the composition in order to trick the eye. Digital stitchery is completed in the off line edit if plates are well-alig ned or in visual effects if plates are radically different and a more complex takeover in needed.
Above is the completed sequence. Notice the extra ref lection element as the actor approaches the window, which was composited separately.