Tutorial 2 - the gemhead and render chains

The next step in understanding GEM involves the use of the gemhead object and building render chains. The gemhead object basically starts the render chain and each subsequent object gets processed in order from top to bottom. The GEM render chain 'flows' through the left inlet of each GEM object. This follows the paradigm of pd and the way it handles messages, signals, and numbers. The left inlet of a GEM object will accept messages just like any pd object.

The gemhead does not 'do' much other than initiate the render chain and also turn the chain on and off using a '1' or '0' message (or a toggle). Turning the gemhead off removes everything after it from the render chain and thus can be used as a way to control CPU usage in large patches. This is an example of using two gemheads for separate processing chains:

The objects after the gemhead, sqaure and triangle are Geos, the next tutorial will cover them in depth, but you can change their size using the number boxes connected to the right inlets. Note that the triangle and square can obscure each other, so choosing which chain to draw is another use for turning the gemhead on and off.