Slit Scan

Updated: Aug 4, 2019

This post is about a well known effect due to its appearance on one of the greatest movies of all time, 2001: A Space Odissey.


I was asked to recreate a similar effect for a project and I did a research in order to achieve it in a simple and effective way. I recommend you as well a fantastic video, as always, made by Filmmaker IQ based on the history of this effect and what Douglas Trumbull, VFX Supervisor in the film, did to achieve it. 

Greeting, also, to JadeLightningDash to cover this effect on his channel done with After Effects.

And thanks to Ivan Busquets and Time Machine, a great tool, he developed based on Houdini's Time Machine, very similar to what Time Displacement does inside After Effects.

Step by step

First of all, you need a base to work on, so in this case I have created 3 different noise, one for each channel. If you wanted to do it more procedurally, a possibility would be to link the evolution parameter, z, with an offset so with one node you would be able to control the 3 noise nodes. However to simplify the process I will do it as it is.

After merging the noises and blurring a bit in order to make the mix a bit more homogeneus, its time to set the key of this effect, the 3d environment. A cylinder would be need in order to project the noise texture on its surface. So a camera and a Scanline render will be needed as well. We will animate the z translation, to make the cylinder move towards camera. Optionally I suggest you tu subtly animate z axis rotation.

Next , we need to mask the end cap of the cylynder with a roto node. This step is optionall but I prefer to do it this way , because you create a vantage ooint whick¡h guides the eye.  

After the main body of the effect it's been done, we need some polishing. In order to make more visual the effect, I crank up the contrast and animate a Hue shift to change its hue along the clip.

Last but not least the final touch, Time Machine. I like to combine the detail of the slit scan pattern with some low frequency distortion therefore we need to generate a noise pattern to guide the Time Machine node through Alpha input. Then set the corresponding offset frames paramter and youre ready to go.

#experiment #stepbystep