Drone Grid Case Study: Creating the Enemies - Beginning Android 3D Game Development - page 292

Finds the angle Theta2 between the NewForwardXZ and the
VehicleToWayPoint vectors.

7.

8. If Theta2 is greater than Theta, turn the tank's main body to the right.

9. If Theta2 is less than Theta, turn the tank's main body to the left.
The SteerVehicleWaypointSpeed() function decelerates the tank around the waypoints. If the tank
is within TurnArea radius of the last waypoint or the current waypoint, this function decelerates the
tank; otherwise, the function accelerates the tank. (See Listing 8-35.)

Listing 8-35. Changing the Speed of the Vehicle Around Waypoints

void SteerVehicleWaypointSpeed(Vector3 WayPoint)
{
// If vehicle is close to waypoint then slow down vehicle
// else accelerate vehicle
Tank AIVehicle = GetParent().GetAIVehicle();

Vector3 VehiclePos = AIVehicle.GetMainBody().m_Orientation.GetPosition();
Vector3 DistanceVecLastWayPoint = Vector3.Subtract(VehiclePos,m_LastWayPoint);
Vector3 DistanceVecCurrentWayPoint = Vector3.Subtract(VehiclePos, m_WayPoint);
float TurnArea = GetParent().GetTurnArea();
float DLastWayPoint = DistanceVecLastWayPoint.Length();
float DCurrentWayPoint = DistanceVecCurrentWayPoint.Length();
if ((DLastWayPoint <= TurnArea) || (DCurrentWayPoint <= TurnArea))
{
// Decrease speed
GetParent().GetAISteering().SetSteeringSpeed(SpeedSteeringValues.Deccelerate, 0.04f,
0.03f, 0.005f);
GetParent().GetAISteering().SetTurnDelta(3.0f);
}
else
{
GetParent().GetAISteering().SetSteeringSpeed(SpeedSteeringValues.Accelerate, 0.04f,
0.03f, 0.005f);
}
}

The SteerVehicleToWayPoint() function steers the vehicle left or right toward the waypoint
location by calling SteerVehicleToWayPointHorizontal() and adjusts the tank's speed by calling
SteerVehicleWaypointSpeed() . (See Listing 8-36.)

Listing 8-36. Steering the Vehicle to the Waypoint

void SteerVehicleToWayPoint(Vector3 WayPoint)
{
SteerVehicleToWayPointHorizontal(WayPoint);
SteerVehicleWaypointSpeed(WayPoint);
}