Summary of Incremental Algorithm on Computing Upper Envelope of a set of Lines
Start with a set of lines, and sort them in increasing slope order.
Take the intersection point of the first line and the next available one.
if (there are other prev intersection pts above that of li & li-1) {discard line li-1;
try intersection pts with previous lines;
take the one that doesn’t have any other points above it.};
add that point to the upper envelope;