On the way to creating some more VJX-basics tutorials I have found myself distracted, hopelessly so, by the topic of feedback. Video feedback is of course a very common and simple “technique”, available in many forms, both hardware and software. However, in most incarnations the result is quite similar and recognizable. Not so with the VJX. The combination of 4 layers, per-layer blend modes and effects, and internal routing create a staggering range of possibilities. I’ve previously posted some examples, and now I’d like take apart and explain the most popular of those, the black and white mirror morph effect.

Vixid Advanced: Feedback Setup and Demo from Create Digital Media on Vimeo.

Input/Patch Setup

Camera or other source feed plugged in to Track 4. Select the appropriate input on Track 4.
Output 1: Connect via patch cable to input on Track 3. S-Video or Composite - Each will give different effects, as will using poor-quality cables, as noise in the patch cable will create more interference in the feedback loop.
Output 2: Connect via patch cable to input on track 2.
Output 3: Final Output - Connect to projector, screen, capture or preview.

The Setup

The VJX is in “Compositing” mode.
Outputs: All set to “Master 1″ (this is what builds the feedback, as the composited output is immediately routed back into tracks 2 and 3).

Track 4: Camera Input. Layer Order D (bottom). BCS (Brightness, Contrast, Saturation) Contrast on 255. Opacity at 100%. This effect works best with a moving, high-contrast, white on black source.
Track 3: First feedback layer. Input from Output 1. Blend Mode: Difference. Layer Order C (second from bottom). Opacity around 40%. Gain 255.
Track 2: Second feedback layer. Input from Output 2. Blend mode: Normal. Layer opacity 25%. Gain 220. Effects: Flip Horizontal, Negative.
Track 1: Not used (could be utilized as an additional feedback loop).

How it Works

The key to this effect is the Negative and Flip effects on track 2. Various combinations of a negative layer applied over a negative blend mode will give you other similar looks. Tweaking the opacity of tracks 2 and 3 will change the “bleed” speed, and depending on the brightness of your source input they may need to be tweaked up or down slightly.

I’m very pleased with this effect. It’s relatively simple to setup, and gives a beautiful, organic look. I’m not sure how well it would work on stage, but it has huge potential for post-production work.

While I’m in a sharing mood. I’ve been spending some time with Feedback effects in the VJX this week, as I was planning to do my next “advanced” tutorial on VJX feedback and effects. However, after losing several hours in experimenting with different blend modes, input and output routing - and creating a huge range of effects and looks - I came to the realization that feedback in the VJX is such a huge topic that we couldn’t hope to cover it properly in a single tutorial.

So instead I’m going to focus on some interesting effects I have discovered, and documenting the exact combination of layers, routing, effects, and other parameters are required to achieve them.

This one is rather complicated. Using the mixer in Battle mode it to isolate two layers as a “feedback loop”, it brings a camera input from track 4, over to the feedback loop on layers 1&2, and then composites them back over the camera input with layer 3. With Difference, Subtraction and Negative blend modes used, and an Inverse effect, I can’t really tell you what’s happening here, but it looks great. The entire effect is controlled with just the gain on the camera input, and tweaking this from 1-255 gives all of the various effects you see in the video.

This one is a little easier, and documented on the Vimeo page. The black/white butterfly effect is achieved by overlaying a Difference blend mode over a layer which is flipped horizontally and has Negative effect applied.

I’ll give proper instruction on creating these effects, and more, soon.