@ agent z, the wiki link you provided me with is not sufficient for me to completely understand the concept. The link simply display a number of different links ranging from mathematics to art which explains what convex means according to the relative subjects. I figure parallax was trying to explain convexity in mathematic terms so my question is which section is relevant to the convex that Parallax is talking about?

* Convex set,

* Convex function,

* Convex polygon,

* Convex hull,

* Convex combination,

* Convex conjugate, or

* Convex optimization

or is it another branch in mathematics not listed here? because i have skim through all of those definition and example and none seem to be describing the decent in height as the sphere curves.