You're pushing arcball really quite hard across this discussion, but it's just one of many ways of handling interactive rotation of an object, and the one used

You're pushing arcball really quite hard across this discussion, but it's just one of many ways of handling interactive rotation of an object, and the one used in the article (give or take accumulating inaccuracy) is fairly normal, too. Certainly, though, the article will not really help anyone aspiring to write a 3d engine of most any kind.