/**
* Check if the number of NPC's in an area are 2 or less.
* @param NPC
* @return
*/
private Boolean lessThanTwoCheck(Node[] NPC)
{
// NPCs are zero
if (NPC.Length == 0)
{
return(true);
}
// create first linked list node.
head = new DblLinkedList(NPC[0]);
prev = head;
if (NPC.Length == 1)
{
return(true);
}
// Else prepare the second linked list.
DblLinkedList DLL_Two = new DblLinkedList(NPC[1]);
head.setNext(DLL_Two);
DLL_Two.setPrev(head);
curr = DLL_Two;
if (NPC.Length == 2)
{
return(true);
}
return(false);
}
public void printCurrList()
{
DblLinkedList Dbl = head;
while (Dbl.getNext() != null)
{
Console.WriteLine("" + Dbl.getNode().id + ", ");
Dbl = Dbl.getNext();
}
Console.WriteLine("" + Dbl.getNode().id);
}
/**
* Same as above but swapped the prev and next X and Y values so the slope intercept formula still works.
* @param NPC
* @param prev
* @param currCheck
* @param trav
* @return
*/
public double hullCheckBottom(Node[] node, DblLinkedList prev, DblLinkedList currCheck, int trav)
{
double prevX = node[trav].xVal;
double prevY = node[trav].yVal;
double nextX = prev.getNode().xVal;
double nextY = prev.getNode().yVal;
double thisX = currCheck.getNode().xVal;
// (3, 2) and (6, 3) // y = mx + b
double slope = (nextY - prevY) / (nextX - prevX); // m
double yInt = prevY - (slope * prevX); // b
// If this is lower than current point, the current point is no longer
// a part of the hull.
return(slope * thisX + yInt);
}
public void setPrev(DblLinkedList n)
{
this.prev = n;
}
public void setNext(DblLinkedList n)
{
this.next = n;
}
public void algoTop(Node[] node)
{
// check if we need to perform a convex hull algorithm.
if (lessThanTwoCheck(node))
{
return;
}
// Go through all but the first and last index's
for (int trav = 2; trav < size; trav++)
{
// find out if the current point is part of the convex hull or not.
double hCheck = hullCheck(node, prev, curr, trav);
DblLinkedList DLL = new DblLinkedList(node[trav]);
/*
* Check if the convex Hull should be outside of the current node
*/
if (hCheck < curr.getNode().yVal)
{
/*
* Check each previous node on the convex hull until up until we are sure no current
* node will be fully contained in the new convex hull.
*/
while (prev != head)
{
/*
* Check each new convex hull compared to the previous node.
*/
double newHullCheck = hullCheck(node, prev.getPrev(), prev, trav);
if (newHullCheck < prev.getNode().yVal)
{
prev = prev.getPrev();
prev.setNext(DLL);
}
/*
* once we verify that we've found a previous convex hull node that won't change from the
* current new node, we quit.
*/
else
{
break;
}
}
/*
* This handles the same situation as directly above but takes care not to go past the
* head.
*/
if (prev == head)
{
double newHullCheck = hullCheck(node, prev, prev.getNext(), trav);
if (newHullCheck < prev.getNode().yVal)
{
prev.setNext(DLL);
}
}
/*
* update the connection between the new next convex hull node and the last verified node
* on the convex hull.
*/
DLL.setPrev(prev);
prev.setNext(DLL);
}
/*
* If the Current Node is Outside the convex hull Then it becomes a part of the new
* convex hull
*/
else
{
curr.setNext(DLL);
DLL.setPrev(curr);
prev = curr;
}
/*
* update the current node along the convex hull.
*/
curr = DLL;
// printCurrList();
}
topEnd = curr;
algoBottom(node);
}
