// Computes a belief distribution for the projectile sources
void computeSourceBeliefs(int playerNum, World world)
{
// Find player
World.Player player = playerNum == 1 ? world.Player1 : world.Player2;
int playerI = World.XToI(player.X);
int playerJ = World.YToJ(player.Y);
sourceI = playerI;
sourceJ = playerJ;
// The initial source is at the player
ProjectileSourceBelief initial = new ProjectileSourceBelief(1.0f, player.Ammo, player.Weapon);
sourceBeliefs.Add(new IJCoords(playerI, playerJ), initial);
// Compute distribution of projectile sources
for (int iter = 0; iter < DistributionSteps; iter++)
{
Dictionary <IJCoords, ProjectileSourceBelief> newBeliefs = new Dictionary <IJCoords, ProjectileSourceBelief>();
float newBeliefsTotal = 0.0f;
// Advance our belief state, except keep the old one around for efficiency
foreach (KeyValuePair <IJCoords, ProjectileSourceBelief> entry in sourceBeliefs)
{
ProjectileSourceBelief belief = entry.Value;
int i = entry.Key.I;
int j = entry.Key.J;
float prior = belief.Probability;
// Determine possible directions
bool upPossible = false;
bool leftPossible = false;
bool rightPossible = false;
bool downPossible = false;
bool stayPossible = false;
int numPossibleDirections = 0;
bool supported = blockWorld.CheckPositionSupported(i, j);
if (!supported)
{
// Can only move down from unsupported positions
numPossibleDirections++;
downPossible = true;
}
else
{
stayPossible = true;
numPossibleDirections++;
if (!blockWorld.CheckGroundByIndex(i, j + 1))
{
downPossible = true;
numPossibleDirections++;
}
if (!blockWorld.CheckGroundByIndex(i + 1, j))
{
leftPossible = true;
numPossibleDirections++;
}
if (!blockWorld.CheckGroundByIndex(i - 1, j))
{
rightPossible = true;
numPossibleDirections++;
}
if (!blockWorld.CheckGroundByIndex(i, j - 1))
{
upPossible = true;
numPossibleDirections++;
}
}
// Compute chance of each direction - uniform
float chance = 1.0f / numPossibleDirections;
float derivedChance = chance * prior;
// Update beliefs based on possible directions
// Staying in place is always an option
if (stayPossible)
{
addBeliefUsingWorld(newBeliefs, i, j, belief, derivedChance, ref newBeliefsTotal);
}
if (upPossible)
{
addBeliefUsingWorld(newBeliefs, i, j - 1, belief, derivedChance, ref newBeliefsTotal);
}
if (downPossible)
{
addBeliefUsingWorld(newBeliefs, i, j + 1, belief, derivedChance, ref newBeliefsTotal);
}
if (leftPossible)
{
addBeliefUsingWorld(newBeliefs, i + 1, j, belief, derivedChance, ref newBeliefsTotal);
}
if (rightPossible)
{
addBeliefUsingWorld(newBeliefs, i - 1, j, belief, derivedChance, ref newBeliefsTotal);
}
}
// Normalize our new belief state
foreach (KeyValuePair <IJCoords, ProjectileSourceBelief> entry in newBeliefs)
{
entry.Value.Probability /= newBeliefsTotal;
}
// Update
sourceBeliefs = newBeliefs;
}
}
