Download the completed project files and sample media for this tutorial.

One of the classic analog techniques for creating amazing visuals in the days before digital was to create video feedback loops. In previous tutorials we have covered the basic idea of how to reproduce this idea within VDMX by using groups with layer taps and FX. In this lesson we'll look at how to take this idea to the next level by introducing composition with alpha channels and masking.

With VDMX there can often be more than one way to go about creating a visual effect and for this tutorial we'll look at two different approaches. In both cases we can use the same starting method of loading in some clips to work with – in this case a blue screen clip and a movie that is encoded with Hap Alpha. When working with the blue screen clip, the Chroma Mask.fs FX is applied to make the blue background pixels invisible during composition.

Using the Zooming Feedback FX

For the first technique, we can simply apply the Zooming Feedback.fs FX from the “Retro” category to the layer. This particular FX can be used with or without footage that has alpha channels, and in this case we will want to switch its blendmode variable to use the alpha channel setting. Additional controls for available for things like adjusting rotation, feedback amount, zoom level and color shifting. Once the final style is created, the layer can be composited over another layer using alpha channels.

Tip: The Zooming Feedback.fs FX is an ISF shader that can be further customized with additional parameters.

Creating A Zooming Feedback Effect using Layers and Groups

While it can often be useful to just pick a single FX from a menu to get a visual style like in part one of this tutorial, often times it can be worthwhile to create the same effect from scratch using layers and groups. As before, we will start with blue screen footage with a chroma mask applied to create alpha channels. However, instead of adding a simple single FX onto the media player layer, this time we will create a rendering group around it and insert a feedback layer. When using OpenGL-Over or VVSourceAtop.fs for composition on the media layer, the alpha channels will be used and the final output will begin to feedback.

Now we can add new FX to the feedback layer in order to get the zooming style and other styles. In particular the Geometry and Color effects can produce interesting results, but try out a lot of different things to find your own unique styles.