I've added the link for reference. But perhaps I should add that pure OpenGL calls are best turned to only as a last resort. For Processing 2.0 an enormous effort has been made to combine the power of OpenGL and GLSL with the ease of use of Processing. All of the difficult stuff is happening under the hood. So look into all the regular routes first. For some more background info see: http://codeanticode.wordpress.com/2013/06/04/processing-2-0-is-out-processing-2-0-is-in/
Only if all else fails, turn to coding in pure OpenGL yourself.
Only if all else fails, turn to coding in pure OpenGL yourself.