/// <summary>
/// UpdateTank runs the AI code that will update the tank's orientation and
/// position. It is very similar to UpdateMouse, but is slightly more
/// complicated: where mouse only has two states, idle and active, the Tank has
/// three.
/// </summary>
private void UpdateTank ()
{
// However, the tank's behavior is more complicated than the mouse's, and so
// the decision making process is a little different.
// First we have to use the current state to decide what the thresholds are
// for changing state, as described in the doc.
float tankChaseThreshold = TankChaseDistance;
float tankCaughtThreshold = TankCaughtDistance;
// if the tank is idle, he prefers to stay idle. we do this by making the
// chase distance smaller, so the tank will be less likely to begin chasing
// the cat.
if (tankState == TankAiState.Wander) {
tankChaseThreshold -= TankHysteresis / 2;
}
// similarly, if the tank is active, he prefers to stay active. we
// accomplish this by increasing the range of values that will cause the
// tank to go into the active state.
else if (tankState == TankAiState.Chasing) {
tankChaseThreshold += TankHysteresis / 2;
tankCaughtThreshold -= TankHysteresis / 2;
}
// the same logic is applied to the finished state.
else if (tankState == TankAiState.Caught) {
tankCaughtThreshold += TankHysteresis / 2;
}
// Second, now that we know what the thresholds are, we compare the tank's
// distance from the cat against the thresholds to decide what the tank's
// current state is.
float distanceFromCat = Vector2.Distance (tankPosition, catPosition);
if (distanceFromCat > tankChaseThreshold) {
// just like the mouse, if the tank is far away from the cat, it should
// idle.
tankState = TankAiState.Wander;
} else if (distanceFromCat > tankCaughtThreshold) {
tankState = TankAiState.Chasing;
} else {
tankState = TankAiState.Caught;
}
// Third, once we know what state we're in, act on that state.
float currentTankSpeed;
if (tankState == TankAiState.Chasing) {
// the tank wants to chase the cat, so it will just use the TurnToFace
// function to turn towards the cat's position. Then, when the tank
// moves forward, he will chase the cat.
tankOrientation = TurnToFace (tankPosition, catPosition, tankOrientation,
TankTurnSpeed);
currentTankSpeed = MaxTankSpeed;
} else if (tankState == TankAiState.Wander) {
// wander works just like the mouse's.
Wander (tankPosition, ref tankWanderDirection, ref tankOrientation,
TankTurnSpeed);
currentTankSpeed = .25f * MaxTankSpeed;
} else {
// this part is different from the mouse. if the tank catches the cat,
// it should stop. otherwise it will run right by, then spin around and
// try to catch it all over again. The end result is that it will kind
// of "run laps" around the cat, which looks funny, but is not what
// we're after.
currentTankSpeed = 0.0f;
}
// this calculation is also just like the mouse's: we construct a heading
// vector based on the tank's orientation, and then make the tank move along
// that heading.
Vector2 heading = new Vector2 (
(float)Math.Cos (tankOrientation), (float)Math.Sin (tankOrientation));
tankPosition += heading * currentTankSpeed;
}
/// <summary>
/// UpdateTank runs the AI code that will update the tank's orientation and
/// position. It is very similar to UpdateMouse, but is slightly more
/// complicated: where mouse only has two states, idle and active, the Tank has
/// three.
/// </summary>
private void UpdateTank()
{
// However, the tank's behavior is more complicated than the mouse's, and so
// the decision making process is a little different.
// First we have to use the current state to decide what the thresholds are
// for changing state, as described in the doc.
float tankChaseThreshold = TankChaseDistance;
float tankCaughtThreshold = TankCaughtDistance;
// if the tank is idle, he prefers to stay idle. we do this by making the
// chase distance smaller, so the tank will be less likely to begin chasing
// the cat.
if (tankState == TankAiState.Wander)
{
tankChaseThreshold -= TankHysteresis / 2;
}
// similarly, if the tank is active, he prefers to stay active. we
// accomplish this by increasing the range of values that will cause the
// tank to go into the active state.
else if (tankState == TankAiState.Chasing)
{
tankChaseThreshold += TankHysteresis / 2;
tankCaughtThreshold -= TankHysteresis / 2;
}
// the same logic is applied to the finished state.
else if (tankState == TankAiState.Caught)
{
tankCaughtThreshold += TankHysteresis / 2;
}
// Second, now that we know what the thresholds are, we compare the tank's
// distance from the cat against the thresholds to decide what the tank's
// current state is.
float distanceFromCat = Vector2.Distance(tankPosition, catPosition);
if (distanceFromCat > tankChaseThreshold)
{
// just like the mouse, if the tank is far away from the cat, it should
// idle.
tankState = TankAiState.Wander;
}
else if (distanceFromCat > tankCaughtThreshold)
{
tankState = TankAiState.Chasing;
}
else
{
tankState = TankAiState.Caught;
}
// Third, once we know what state we're in, act on that state.
float currentTankSpeed;
if (tankState == TankAiState.Chasing)
{
// the tank wants to chase the cat, so it will just use the TurnToFace
// function to turn towards the cat's position. Then, when the tank
// moves forward, he will chase the cat.
tankOrientation = TurnToFace(tankPosition, catPosition, tankOrientation,
TankTurnSpeed);
currentTankSpeed = MaxTankSpeed;
}
else if (tankState == TankAiState.Wander)
{
// wander works just like the mouse's.
Wander(tankPosition, ref tankWanderDirection, ref tankOrientation,
TankTurnSpeed);
currentTankSpeed = .25f * MaxTankSpeed;
}
else
{
// this part is different from the mouse. if the tank catches the cat,
// it should stop. otherwise it will run right by, then spin around and
// try to catch it all over again. The end result is that it will kind
// of "run laps" around the cat, which looks funny, but is not what
// we're after.
currentTankSpeed = 0.0f;
}
// this calculation is also just like the mouse's: we construct a heading
// vector based on the tank's orientation, and then make the tank move along
// that heading.
Vector2 heading = new Vector2(
(float)Math.Cos(tankOrientation), (float)Math.Sin(tankOrientation));
tankPosition += heading * currentTankSpeed;
}