The following post has been created and released because you lovely people out there have between you contributed over £900 to the post-production funding of my fantasy-drama Stop/Eject. Visit stopejectmovie.com to become part of the project if you haven’t already.

Since Stop/Eject is still being edited, work has not yet begun on the visual effects for the film itself, but the trailer we released in May features three representative FX shots and it’s these that I’m now going to take you through. First, watch the trailer if you haven’t already.

And here’s the breakdown video. A full explanation of the steps involved can be found below.

Dan’s Death

This is a key shot and was carefully planned. I wanted it to be in slow motion, but the Canon 600D we used can only over-crank to 50 frames per second if the resolution is lowered from 1080P (full HD) to 720P. I built this limitation into the VFX design.

Firstly a wide shot of the shop facade was recorded at 1080P25. This was deliberately done in the morning, when the shop was in the sun and the opposite side of the street was in the shade, in order to minimise the genuine reflections. Then Kate (Georgina Sherrington) was shot emerging from the shop at 720P50, with the camera mounted on its side and framed solely on the doorway. This slow motion element could then be placed within the larger 1080P25 frame recorded earlier, maintaining the image resolution.

Dan (Oliver Park) and the car were shot in a car park with a locked-off camera, the former at 720P50 to ensure his movements matched the slow motion of Kate’s, and the latter at 1080P25 with the car driving at half the speed it should have been. These two elements were combined with a simple feathered crop. The collision will never be seen, so he simply vanishes at the critical moment. I figured the lower resolution of Dan would not be noticeable once this element was composited as a reflection.

In Photoshop, I created an alpha matte of the shop’s windows and door. I applied this to the Dan/car composite, then layered it on top of the Georgina/shop composite with an opacity of about 50% to give the impression of a reflection.

The door’s alpha matte was key-framed to distort as Kate opens it. The final step was to animate this part of the reflection to pan sideways with motion blur and fade out as the door opens.

Ghostly Kate

Kate and Dan were shot separately for this, with the camera locked off. For both elements I created a difference matte in Final Cut, whereby the computer compares the element with a base image, in this case the same locked-off shot without either character present. I could then important these mattes into Shake and clean them up using rotoshapes and Quickpaint nodes.

Further use of these tools was made to animate the intersection of the two characters, revealing Kate little by little as she passes through Dan, all the time striving to give the impression that both bodies are three-dimensional. (Here I drew on many über-geeky teenage hours spent watching VFX shots in Quantum Leap and Red Dwarf frame by frame on my VCR, admiring the artistry and trying to figure out the technical trickery.)

After subtracting one matte from the other, I imported the result back into Final Cut and applied it to the original Dan element, placing the Kate element beneath to generate the final composite. A separate, static matte for the foreground records was used to layer them back on top, and an artificial camera move was applied to the whole thing to take the curse off the locked-off look. This move was possible without loss of image quality since we had shot 16:9 but were masking to 2.35:1, so we had surplus material at the top and bottom of frame.

Tape Archive

Hopefully you didn’t even spot that this was a VFX shot. Sophie spent many sleepless nights labelling hundreds of cassette cases for the basement scene, but even these represented only a small fraction of the number required to fill the master shot. Therefore it was always planned to lock off the camera and fill in the missing tapes digitally.

I started by exporting a single frame to Photoshop, where I used primarily good old copy-and-paste, plus a bit of airbrushing and a lot of distorting and resizing, to clone the real tapes many times over. I then imported this layered file into Final Cut.

Next came the most time-consuming part. Hold-out mattes had to be generated for Kate and Alice (Therese Collins) to keep them in front of the cloned tapes. These were created in Shake as rotoshapes and key-framed every few frames to follow the characters’ movements. Once applied back in Final Cut, the foreground characters and falling tapes appear to occlude the digital tapes in the background as you would expect.

That’s all, folks. Please keep the donations coming. We’re just £43 away from the £1,000 mark and the next public reward – the podcast covering day four of the shoot.