Shadow

has anyone worked with shado visualization on grasshopper?
i came through some definitions but they only projected the shadows on one plane at a time.
i couldn't adapt them to work like realtime shadow (like sketchup's) but i reckon it would be of great use during design process.
thank you!

this is the one i was trying to modify http://www.tedngai.net/experiments/incident-solar-current-time.html