Assignment 4, due Tuesday, May 17, is to make an audio-driven computer graphic, such as the one shown in class:

It doesn't have to be a bird; it could be abstract. And it doesn't have to feature a moving "mouth" - it could be something else that grows and shrinks, or changes color, or whatnot. Use your creativity...

To do this:

• Get Gem running on your machine. This might be the trickiest part... some hints are below. Try loading the patches in this directory to see if it's working and review the class materials.
• Make an assemblage of polygons of various colors, that makes a pleasing visual design, perhaps more pleasing than mine:). The "translate" object makes it easy to move them around to assemble a final product.
• Connect an audio input to an envelope follower. You can probably just use an adc~ object and put a CD in your computer (making sure to turn up the "CD" channel of your soundcard's mixer using the audio control panel for your OS. Please include a "receive input" object in the patch to make it easier for David to test the patch. A possible setup is shown:
  
• Use an env~ object to measure the time-varying power of the input signal. It's OK to use the default speed (higher than you really need), or you can feed "env" a parameter (1024 for 80 points a second, 2048 for 40, for instance.
• Use the env~ output to modify the vertices or color of some or even all the polygons in the "gem" patch. Bearing in mind that coordinates in Gem typically range from -4 to 4, and color values (RGB or HSV) from 0 to 1, you'll have to adjust the units of the env~ output appropriately. It often doesn't work well to scale the output in dB (the units env~ uses)... RMS amplitude or power might be more appropriate, or you can even use arrays to make explicit functions from dB to the desired controls.
• set up a "gemwin" object, and messages to create the window and start rendering, so it's easy to start the patch up.
• I used the "color" message to the gemwin object to make the background blue-green; you might have to do something similar.

For extra credit, find a meaningful way to use more than one sonic dimension to control two or more aspects of the picture. This could be done using filters to single out frequency ranges (like patch 6 in this directory), or make discrete changes triggered by a threshold, or use different time delays on the envelope follower output.

Notes on getting gem to run:

Gem is available from https://gem.iem.at/ . Note the useful instructions on: https://gem.iem.at/download/GEM.README.

To run Gem on the ACS PCs in B104, first download Gem, to your desktop for example. There should be a file, "Gem.dll" in the distribution for PCs. (If necessary fix the PC to show you "invisible files" such as dlls.) Figure out the full pathname (maybe it's \blabla\...\Desktop\Gem\Gem.dll or something). Then browse inside the Pd installation to find the executable (something like \Program files\...\pd\bin\pd.exe) and make a shortcut to it on your desktop. Edit the shortcut to start in the directory you downloaded, so that Pd starts in the directory \blabla\...\Desktop\Gem and the "command" reads like:

    "\Program files\...\pd\bin\pd.exe -lib Gem"

I don't know how this works out in Mac OSX yet... if you're having trouble let's figure it out in office hours.