Using Adobe Premiere – [post] — (without After Effects).
Here is a first graphic presentation and explanation to accompany the last 15 seconds of this working example. There was going to be a separate description of creating a tracking mask necessary for items which move over existing background, such as the angled view of the raising stair at 7-15 seconds in this clip. However, this method proved to be very time-consuming and frustrating with the saw-tooth shape of the stairway — it produced unclean results and was abandoned the moment we tested a method based on a combination of colour keying and less critical video masking. Results are described and shown in ‘black screen & mask‘.
The whole exercise of integration is much simpler when the moving part moves over another part of the model (such as the raising stair moving over the fixed stair) or in front of a black background (as for the raising stair when it opens completely). An alternative technique would be to have the moving element move in front of a photograph as a printed background or displayed on a screen (similar to techniques used in ‘time warp‘ from 2008 and 2018).