/// <summary>
/// Find the vector telling next location to go to.
/// if fails to find a solution, it returns the target by default
/// </summary>
/// <param name='position'>
/// Position.
/// </param>
/// <param name='target'>
/// Target.
/// </param>
/// <param name='mapInfo'>
/// LevelInfo containing info on the level.
/// </param>
public static Vector2 Find(Vector2 position, Vector2 target, LevelInfo mapInfo)
{
if (canGoStraightLine(position, target, mapInfo)) return target;
Vector2 defaultRtrnLoc = target; // by default tell to go straight to target
if (!mapInfo.inBounds(position)) {
// this SHOULDN'T happen, you should not be out of bounds of the level
return defaultRtrnLoc;
}
int xPos = (int)position.x;
int yPos = (int)position.y;
int xTarget = (int)target.x;
int yTarget = (int)target.y;
// use 3th dimension to store c(p) in f(p) = h(p) + c(p)
PriorityQueue<Vector3> frontier = new PriorityQueue<Vector3>();
// add start position to frontier
int cp = 0;
int fp = getHP(position, target) + cp;
frontier.enqueue(fp, new Vector3(xPos, yPos, cp));
// backtracking (cpsc320 anyone?)
// might not be the optimal method, but it works
// Vector3, x, y map to coords, z is used for cost
// z = -1 if visited, non-neg integer if not visited = cost to reach location
Vector3[,] backtrack = new Vector3[(int)mapInfo.getSize().x, (int)mapInfo.getSize().y];
// set the backtrack for position to -1,-1
backtrack[xPos, yPos] = new Vector3(-1, -1, 1);
for (int i = 0; i < STEP_LIMIT; i++) {
if (frontier.isEmpty()) {
return defaultRtrnLoc; // can't reach it...
}
// select lowest f(p) = h(p) + c(p)
Vector3 nextDequeue = frontier.dequeue();
Vector2 nextLocation = new Vector2(nextDequeue.x, nextDequeue.y);
// double check that this location has not been visited
if (backtrack[(int)nextLocation.x, (int)nextLocation.y].z == -1) {
continue;
}
// check if goal
if ((int)nextLocation.x == xTarget && (int)nextLocation.y == yTarget) {
// backtrack from this position....
// find first step to move
return getBacktrack(backtrack, target, position, mapInfo);
}
// mark location as accessed
backtrack[(int)nextLocation.x, (int)nextLocation.y].z = -1;
bool verify_diag = false;
// otherwise add neighbour of those to frontier that:
for (int deltaX = -1; deltaX <= 1; deltaX++) {
for (int deltaY = -1; deltaY <=1; deltaY++) {
verify_diag = false;
if (NO_DIAGONAL_MOVEMENT && (deltaX * deltaY != 0)) {
continue;
} else {
if (deltaX * deltaY != 0) {
// verify that we can actually move diagonally
verify_diag = true;
}
}
Vector2 neighbour = nextLocation + new Vector2(deltaX, deltaY);
int thisCP = (int)nextDequeue.z + Mathf.Abs(deltaX * deltaY) * DIAG_COST
+ LINEAR_COST;
int thisFP = getHP(neighbour, target) + thisCP;
// a) is within boundaries
if (!mapInfo.inBounds(neighbour)) { continue; }
// b) have not been visited or it's cheaper to go this way
Vector3 locInfo = backtrack[(int)neighbour.x, (int)neighbour.y];
if (locInfo != Vector3.zero && locInfo.z < thisCP) { continue; }
// c) are accessible from this location (walkable as specified by mapInfo)
if (mapInfo.isOccupiedBy(neighbour, MapScript.ENEMY_GROUP)) { continue; }
if (verify_diag) {
if (mapInfo.isOccupiedBy(nextLocation + new Vector2(0, deltaY),
MapScript.ENEMY_GROUP)) { continue; }
if (mapInfo.isOccupiedBy(nextLocation + new Vector2(deltaX, 0),
MapScript.ENEMY_GROUP)) { continue; }
}
// all criteria satisfied
// add to frontier
frontier.enqueue(thisFP, new Vector3(neighbour.x, neighbour.y, thisCP));
// add to allow backtrack
backtrack[(int)neighbour.x, (int)neighbour.y] =
new Vector3(nextLocation.x, nextLocation.y, thisCP);
}
}
}
// outta steps, return the closest one found so far
if (frontier.isEmpty()) {
return defaultRtrnLoc; // can't reach it...don't move?
} else {
Vector3 nextDequeue = frontier.dequeue();
Vector2 nextLocation = new Vector2(nextDequeue.x, nextDequeue.y);
return getBacktrack(backtrack, nextLocation, position, mapInfo);
}
}
/***
* Flee A* implementation
* - what this does is similiar to A*. It searches and returns the location with the highest "distance"
* from the player. It has a limit to the distance it is willing to search (o), and it has a distance
* that it (P) refuses to come close to (x) the target (T)
*
* Think of it as a donut shape centered around the target. The width of the donut depends on the distance
* between the position and the target
* --------------------------
* | ooooooooo |
* | oooooxooooo |
* |ooPooxxxooooo |
* |ooooxxTxxooooo |
* |oooooxxxooooo |
* | oooooxooooo |
* | ooooooooo |
* -------------------------
*
* */
public static Vector2 Flee(Vector2 position, Vector2 target, LevelInfo mapInfo)
{
float minDistancePercentage = 50.0f; //%
float maxDistancePercentage = 350.0f; //%
// if position and target are "r" units apart
// will find cheapest path to farthest location that does not get within r*50% of
// target, and no farther than r*350% of target
// (of course, if this is repeatedly called, as you get farther from target
// your search range increases
// Alternatively, think of it as how "panic'd" the AI is.
// if a AI running away from the target is really close
// it will "panic" and simply tries to get slightly farther away
// as it reaches farther away, it "relaxes" and makes a better analysis of the
// possible paths.
float distance = getDistance(position, target);
int minDistance = (int)(distance * minDistancePercentage / 100.0f) - 1;
int maxDistance = (int)(distance * maxDistancePercentage / 100.0f) + 1;
Vector2 defaultRtrnLoc = position;//position + (position - target); // by default tell to go away
if (!mapInfo.inBounds(position)) {
// this SHOULDN'T happen, you should not be out of bounds of the level
return defaultRtrnLoc;
}
int xPos = (int)position.x;
int yPos = (int)position.y;
// never go farther than twice the distance (computational resource reasons)
// use 3rd dimension to store c(p) in f(p) = h(p) + c(p)
PriorityQueue<Vector3> frontier = new PriorityQueue<Vector3>();
// farthest location so far
Vector2 farthestPoint = position;
int farthestPointFP = int.MaxValue;
// add start position to frontier
int cp = 0;
int fp = getFleeHP(position, target) + cp;
frontier.enqueue(fp, new Vector3(xPos, yPos, cp));
// backtracking (cpsc320 anyone?)
// might not be the optimal method, but it works
// Vector3, x, y map to coords, z is used for cost
// z = -1 if visited, non-neg integer if not visited = cost to reach location
Vector3[,] backtrack = new Vector3[(int)mapInfo.getSize().x, (int)mapInfo.getSize().y];
// set the backtrack for position to -1,-1
backtrack[xPos, yPos] = new Vector3(-1, -1, 1);
for (int i = 0; i < STEP_LIMIT; i++) {
if (frontier.isEmpty()) {
//return defaultRtrnLoc; // can't reach it...
return getBacktrack(backtrack, farthestPoint);
}
// select lowest f(p) = h(p) + c(p)
Vector3 nextDequeue = frontier.dequeue();
Vector2 nextLocation = new Vector2(nextDequeue.x, nextDequeue.y);
// double check that this location has not been visited
if (backtrack[(int)nextLocation.x, (int)nextLocation.y].z == -1) {
continue;
}
// mark location as accessed
backtrack[(int)nextLocation.x, (int)nextLocation.y].z = -1;
bool verify_diag = false;
// otherwise add neighbour of those to frontier that:
for (int deltaX = -1; deltaX <= 1; deltaX++) {
for (int deltaY = -1; deltaY <=1; deltaY++) {
verify_diag = false;
if (NO_DIAGONAL_MOVEMENT && (deltaX * deltaY != 0)) {
continue;
} else {
if (deltaX * deltaY != 0) {
// verify that we can actually move diagonally
verify_diag = true;
}
}
Vector2 neighbour = nextLocation + new Vector2(deltaX, deltaY);
float neighbourDistance = getDistance(neighbour, target);
int thisCP = (int)nextDequeue.z + Mathf.Abs(deltaX * deltaY) * DIAG_COST
+ LINEAR_COST;
// increase the cost if it means we have to go CLOSER to the target (than originally)
// if (neighbourDistance > distance && neighbourDistance > 3) {
// thisCP += (int)(neighbourDistance - distance);
// }
int thisFP = getFleeHP(neighbour, target) + thisCP;
// a) is within boundaries
if (!mapInfo.inBounds(neighbour)) { continue; }
// b) have not been visited or it's cheaper to go this way
Vector3 locInfo = backtrack[(int)neighbour.x, (int)neighbour.y];
if (locInfo != Vector3.zero && locInfo.z < thisCP) { continue; }
// c) are accessible from this location (walkable as specified by mapInfo)
if (mapInfo.isOccupiedBy(neighbour, MapScript.ENEMY_GROUP)) { continue; }
if (verify_diag) {
if (mapInfo.isOccupiedBy(nextLocation + new Vector2(0, deltaY),
MapScript.ENEMY_GROUP)) { continue; }
if (mapInfo.isOccupiedBy(nextLocation + new Vector2(deltaX, 0),
MapScript.ENEMY_GROUP)) { continue; }
}
// d) within our search bounds
if (neighbourDistance < minDistance || neighbourDistance > maxDistance) {
continue;
}
// UPDATE farthestPOINT!
if (thisFP < farthestPointFP) {
farthestPoint = neighbour;
farthestPointFP = thisFP;
}
// all criteria satisfied
// add to frontier
frontier.enqueue(thisFP, new Vector3(neighbour.x, neighbour.y, thisCP));
// add to allow backtrack
backtrack[(int)neighbour.x, (int)neighbour.y] =
new Vector3(nextLocation.x, nextLocation.y, thisCP);
}
}
}
// outta steps, return the closest one found so far
if (frontier.isEmpty()) {
return getBacktrack(backtrack, farthestPoint); // can't reach it, return farthest found so far
} else {
Vector3 nextDequeue = frontier.dequeue();
Vector2 nextLocation = new Vector2(nextDequeue.x, nextDequeue.y);
return getBacktrack(backtrack, nextLocation);
}
}
