Don't mean to sound arrogant, but it's not really worth doing that rendering. I can if you really want it, but you can easily see from this picture (stolen from
www.ledgroupbuy.com ) that it essentially spreads the light everywhere. However, this is misleading, as one can see by the intensity vs angle graph on the LED's data sheet how much more intense it'd be at the center. I suppose one could do a sort of rendering combined with the intensity vs angle incorporated, but I'm not that smart.
Graph at bottom of page 6:
http://www.cree.com/products/pdf/XLampXP-G.pdf