My First Quartz Composition

Quartz composer is often used for making screensavers. So, to learn QC, I decided to make a screensaver of my own. I started with a simple concept, two spheres orbiting around each other. I thought it would be simple anyway. All of the motion is accomplished through the use of LFOs (low-frequency oscillators). At first, I thought I could use three LFOs, one for each axis, to generate the desired motion. I couldn’t find anyway to get this to work. In the end, I found an alternative solution. Each sphere has two LFOs that cause the sphere to orbit in the yz-plane. From there, I used a 3D transformation patch to rotate the two spheres about the y and z axes. This achieved the movement I mentally envisioned. Much of my efforts were trial and error. There is very little documentation available for QC. I hope this to change in time.

Below is a link to my Quartz Composition for anyone interested.

http://dl.dropbox.com/u/2998162/Quartz%20Composer/Orbiting_Spheres.qtz

My First Quartz Composer Patches

While playing around with some of the standard Quartz Composer patches, I discovered the Apple remote patch. I just so happen to have an Apple remote, so I wanted to give it a try. I found it to work well. However, the remote only emitted a quick “true” signal. For what I wanted to do, I needed to store a boolean state. A previous electrical engineering course helped me come up with the solution. I built an RS flip flop patch. An RS flip flop is a simple electrical circuit that stores a single state. It consists of only two NOR gates that are cross-coupled. By setting one wire high (true) the stored bit will go high. When the other wire is set high, the stored bit will go low (false). While both wires are low, the bit will remain unchanged. However, both wires shouldn’t ever both be set high. The result is undefined.

This new patch suited me well. The only problem was that it required using two buttons and those buttons couldn’t be pressed simultaneously. I, of course, could do better. I added a few more components to my patch and changed it to a toggle switch. This permitted one button to toggle between the two states. I later discovered that there is a standard toggle patch, but it can toggle between any two numbers. Mine specifically uses boolean values.

Below are links to download the two patches I developed for those who are interested. Note that since these are patches, not macros, the underlying logic is not available to view.

http://dl.dropbox.com/u/2998162/Quartz%20Composer/RS_Flip_Flop.qtz
http://dl.dropbox.com/u/2998162/Quartz%20Composer/Toggle_Switch.qtz