Nitty-gritty details of the most complex parts of a drop-cutter algorithm for filleted endmills. First hacked together in around 2007, but now by popular demand some diagrams and explanations:
http://www.anderswallin.net/2014/02/drop-cutter-toroid-edge-test/
http://www.anderswallin.net/2014/02/drop-cutter-toroid-edge-test