func (f *Fov) process(origin space.Location, radius int, begin, end angle) {
if begin.radius > radius {
return
}
group := f.group(origin, begin.point())
for a := begin; a.isBelow(end); a = a.next() {
pt := a.point()
if f.group(origin, pt) != group {
// The type of terrain changed, recurse a deeper process with
// current arc and start a new arc.
if !group.blocksSight {
f.process(origin.Beyond(group.portal), radius, begin.above(), a.above())
}
f.process(origin, radius, a, end)
return
}
f.markSeen(pt, f.mf.Offset(origin, pt))
}
// Recurse after finishing the whole arc.
if !group.blocksSight {
f.process(origin.Beyond(group.portal), radius, begin.above(), end.above())
}
}
func (f *Fov) group(origin space.Location, offset image.Point) group {
rawLoc := origin.Add(offset)
return group{f.blocksSight(f.mf.Traverse(rawLoc)), f.mf.Portal(rawLoc)}
}