The easy way to get started with Shadertoy and JRubyArt or PiCrate, just insert the shadertoy code as required in the default_shader. Run the sketch then remove any unnecessary parameters and you are ready to go. You could then refactor to be more in line with codeanticode sketches..
archive-for-processing/shadertoy2jruby_art
Easy way to get started with Shadertoy and JRubyArt
RubyAGPL-3.0