Recently at work, I needed a clean exterior shot of a specific location. Unfortunately the only thing the camera operator shot was a “walky” (talent walking towards or away from camera), that covered almost all of the building. The style of the footage is handheld and a bit dynamic, while cars pass by, reflected in the windows.
To reconstruct the shot I start with the wobbly footage and 2 still frames taken from portions of the same shot that don’t include the person.
In the Movie Clip Editor or MCE, otherwise known as the Motion Tracker, I select 4 high contrast regions of the first frame and perform a track forward.
Once I have 4 good tracks, to the end of the shot, I can create a Plane track. To do this I must make sure I select all 4 tracks.
But the Plane that is created is currently to small, if I use this the still images will be shrunk to fit this shape. My still frames were the same size as the source image, so I need to stretch it out.
I grab each corner and fit them to the original frame, they must be exact.
Next I use the UV/Image editor to create 2 masks, that will cover the path traced out by the man walking. I make one for each still image. This will mean that any moment occurring inside the mask will be replaced with a static image. Fortunately the reflections of passing cars were not obvious in the adjacent window.
Moving over to the compositor I start by adding:
- A. Original wobbly shot
- B. 2 Still images
- 1. Transform node to line up the image with the first frame of shot
- 2. Mask node that cuts out the shape of the still image required
- 3. Set alpha node to attach the cut out shape to the image.
- 4. Apply the tracked motion using a Plane Track Deform
- 5. Alpha Over node to place the first still image onto the background wobbly clip.
- 6. Another Alpha over node to place the second still image onto the previous composite.
Well its more impressive when it plays back.