How To: Create audio-reactive effects for GrandVJ with Quartz Composer
Feb/100
In GrandVJ 1.2 we have introduced the support for Quartz Compositions, either as visual or as effect. Note that MediaMaster 1.2 will also support Quartz Compositions, so you can use this with MediaMaster 1.2 too (the beta can be found on our forums)
Quartz Composer is a free graphics and imaging tool on the Mac platform which is available as an optional install that can be found on your Mac OS X DVD since version 10.4.
It allows very easy creation of complex audio-reactive animations or effects which can now be played in GrandVJ (read the previous article about GrandVJ and Quartz Composer). As I’m writing these lines, the last version of Quartz-Composer is 4.0 on Mac OS 10.6 (Snow Leopard).
In this article we will demonstrate how to quickly create a bass-reactive Zoom/Blur effect like the one you can see below:
Important: This tutorial requires that you have some basic knowledge of Quartz Composer: if you have never used it, you really should first go through the “Getting Started”. You will also find some helpful readings at the Apple Developer Connection web site about Quartz Composer.
To create our effect we will simply edit Quartz-Composer’s default template named “Image Filter” to make it audio reactive. Basically, we will connect bass levels of the computer’s audio input signal to the “Amount” parameter of our Zoom/Blur filter. (Read more below..)
Quartz Composer integration in GrandVJ 1.2
Nov/095
GrandVJ 1.2 now allows to use Quartz Composer .qtz files directly, both as sources and effects. In older versions it was necessary to save them as QuickTime movies with the big drawbacks that it was slow and it did not allow to change compositions variables.
We have optimized the Quartz Composer integration in GrandVJ 1.2 so that the compostions are rendered natively through the fastest available interface.
Finally, when using a composition as an effect the application will scan the published inputs and map them as effect parameters, if the format is compatible with the engine. GrandVJ can automatically map parameters that are float values, indexes, colors and booleans and there’s one visual input of the composition that receive the cell visual.
Now let’s have a quick look at how you can use Quartz compositions with GrandVJ..
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