linepick is simple
p=linepick( entityx(npc),entityy(npc),entityz(npc), entityx(camera)-entityx(npc),entityy(camera)-entityy(npc),entityz(camera)-entityz(npc) )
p=linepick( entityx(npc),entityy(npc),entityz(npc), entityx(camera)-entityx(npc),entityy(camera)-entityy(npc),entityz(camera)-entityz(npc) )