using System;
using UnityEngine;
using Random = UnityEngine.Random;
#pragma warning disable 649
namespace UnityStandardAssets.Vehicles.Car
{
[RequireComponent(typeof (CarController))]
public class CarAIControl : MonoBehaviour
{
public enum BrakeCondition
{
NeverBrake, // the car simply accelerates at full throttle all the time.
TargetDirectionDifference, // the car will brake according to the upcoming change in direction of the target. Useful for route-based AI, slowing for corners.
TargetDistance, // the car will brake as it approaches its target, regardless of the target's direction. Useful if you want the car to
// head for a stationary target and come to rest when it arrives there.
}
// This script provides input to the car controller in the same way that the user control script does.
// As such, it is really 'driving' the car, with no special physics or animation tricks to make the car behave properly.
// "wandering" is used to give the cars a more human, less robotic feel. They can waver slightly
// in speed and direction while driving towards their target.
[SerializeField] [Range(0, 1)] private float m_CautiousSpeedFactor = 0.05f; // percentage of max speed to use when being maximally cautious
[SerializeField] [Range(0, 180)] private float m_CautiousMaxAngle = 50f; // angle of approaching corner to treat as warranting maximum caution
[SerializeField] private float m_CautiousMaxDistance = 100f; // distance at which distance-based cautiousness begins
[SerializeField] private float m_CautiousAngularVelocityFactor = 30f; // how cautious the AI should be when considering its own current angular velocity (i.e. easing off acceleration if spinning!)
[SerializeField] private float m_SteerSensitivity = 0.05f; // how sensitively the AI uses steering input to turn to the desired direction
[SerializeField] private float m_AccelSensitivity = 0.04f; // How sensitively the AI uses the accelerator to reach the current desired speed
[SerializeField] private float m_BrakeSensitivity = 1f; // How sensitively the AI uses the brake to reach the current desired speed
[SerializeField] private float m_LateralWanderDistance = 3f; // how far the car will wander laterally towards its target
[SerializeField] private float m_LateralWanderSpeed = 0.1f; // how fast the lateral wandering will fluctuate
[SerializeField] [Range(0, 1)] private float m_AccelWanderAmount = 0.1f; // how much the cars acceleration will wander
[SerializeField] private float m_AccelWanderSpeed = 0.1f; // how fast the cars acceleration wandering will fluctuate
[SerializeField] private BrakeCondition m_BrakeCondition = BrakeCondition.TargetDistance; // what should the AI consider when accelerating/braking?
[SerializeField] private bool m_Driving; // whether the AI is currently actively driving or stopped.
[SerializeField] private Transform m_Target; // 'target' the target object to aim for.
[SerializeField] private bool m_StopWhenTargetReached; // should we stop driving when we reach the target?
[SerializeField] private float m_ReachTargetThreshold = 2; // proximity to target to consider we 'reached' it, and stop driving.
private float m_RandomPerlin; // A random value for the car to base its wander on (so that AI cars don't all wander in the same pattern)
private CarController m_CarController; // Reference to actual car controller we are controlling
private float m_AvoidOtherCarTime; // time until which to avoid the car we recently collided with
private float m_AvoidOtherCarSlowdown; // how much to slow down due to colliding with another car, whilst avoiding
private float m_AvoidPathOffset; // direction (-1 or 1) in which to offset path to avoid other car, whilst avoiding
private Rigidbody m_Rigidbody;
private void Awake()
{
// get the car controller reference
m_CarController = GetComponent<CarController>();
// give the random perlin a random value
m_RandomPerlin = Random.value*100;
m_Rigidbody = GetComponent<Rigidbody>();
}
private void FixedUpdate()
{
if (m_Target == null || !m_Driving)
{
// Car should not be moving,
// use handbrake to stop
m_CarController.Move(0, 0, -1f, 1f);
}
else
{
Vector3 fwd = transform.forward;
if (m_Rigidbody.velocity.magnitude > m_CarController.MaxSpeed*0.1f)
{
fwd = m_Rigidbody.velocity;
}
float desiredSpeed = m_CarController.MaxSpeed;
// now it's time to decide if we should be slowing down...
switch (m_BrakeCondition)
{
case BrakeCondition.TargetDirectionDifference:
{
// the car will brake according to the upcoming change in direction of the target. Useful for route-based AI, slowing for corners.
// check out the angle of our target compared to the current direction of the car
float approachingCornerAngle = Vector3.Angle(m_Target.forward, fwd);
// also consider the current amount we're turning, multiplied up and then compared in the same way as an upcoming corner angle
float spinningAngle = m_Rigidbody.angularVelocity.magnitude*m_CautiousAngularVelocityFactor;
// if it's different to our current angle, we need to be cautious (i.e. slow down) a certain amount
float cautiousnessRequired = Mathf.InverseLerp(0, m_CautiousMaxAngle,
Mathf.Max(spinningAngle,
approachingCornerAngle));
desiredSpeed = Mathf.Lerp(m_CarController.MaxSpeed, m_CarController.MaxSpeed*m_CautiousSpeedFactor,
cautiousnessRequired);
break;
}
case BrakeCondition.TargetDistance:
{
// the car will brake as it approaches its target, regardless of the target's direction. Useful if you want the car to
// head for a stationary target and come to rest when it arrives there.
// check out the distance to target
Vector3 delta = m_Target.position - transform.position;
float distanceCautiousFactor = Mathf.InverseLerp(m_CautiousMaxDistance, 0, delta.magnitude);
// also consider the current amount we're turning, multiplied up and then compared in the same way as an upcoming corner angle
float spinningAngle = m_Rigidbody.angularVelocity.magnitude*m_CautiousAngularVelocityFactor;
// if it's different to our current angle, we need to be cautious (i.e. slow down) a certain amount
float cautiousnessRequired = Mathf.Max(
Mathf.InverseLerp(0, m_CautiousMaxAngle, spinningAngle), distanceCautiousFactor);
desiredSpeed = Mathf.Lerp(m_CarController.MaxSpeed, m_CarController.MaxSpeed*m_CautiousSpeedFactor,
cautiousnessRequired);
break;
}
case BrakeCondition.NeverBrake:
break;
}
// Evasive action due to collision with other cars:
// our target position starts off as the 'real' target position
Vector3 offsetTargetPos = m_Target.position;
// if are we currently taking evasive action to prevent being stuck against another car:
if (Time.time < m_AvoidOtherCarTime)
{
// slow down if necessary (if we were behind the other car when collision occured)
desiredSpeed *= m_AvoidOtherCarSlowdown;
// and veer towards the side of our path-to-target that is away from the other car
offsetTargetPos += m_Target.right*m_AvoidPathOffset;
}
else
{
// no need for evasive action, we can just wander across the path-to-target in a random way,
// which can help prevent AI from seeming too uniform and robotic in their driving
offsetTargetPos += m_Target.right*
(Mathf.PerlinNoise(Time.time*m_LateralWanderSpeed, m_RandomPerlin)*2 - 1)*
m_LateralWanderDistance;
}
// use different sensitivity depending on whether accelerating or braking:
float accelBrakeSensitivity = (desiredSpeed < m_CarController.CurrentSpeed)
? m_BrakeSensitivity
: m_AccelSensitivity;
// decide the actual amount of accel/brake input to achieve desired speed.
float accel = Mathf.Clamp((desiredSpeed - m_CarController.CurrentSpeed)*accelBrakeSensitivity, -1, 1);
// add acceleration 'wander', which also prevents AI from seeming too uniform and robotic in their driving
// i.e. increasing the accel wander amount can introduce jostling and bumps between AI cars in a race
accel *= (1 - m_AccelWanderAmount) +
(Mathf.PerlinNoise(Time.time*m_AccelWanderSpeed, m_RandomPerlin)*m_AccelWanderAmount);
// calculate the local-relative position of the target, to steer towards
Vector3 localTarget = transform.InverseTransformPoint(offsetTargetPos);
// work out the local angle towards the target
float targetAngle = Mathf.Atan2(localTarget.x, localTarget.z)*Mathf.Rad2Deg;
// get the amount of steering needed to aim the car towards the target
float steer = Mathf.Clamp(targetAngle*m_SteerSensitivity, -1, 1)*Mathf.Sign(m_CarController.CurrentSpeed);
// feed input to the car controller.
m_CarController.Move(steer, accel, accel, 0f);
// if appropriate, stop driving when we're close enough to the target.
if (m_StopWhenTargetReached && localTarget.magnitude < m_ReachTargetThreshold)
{
m_Driving = false;
}
}
}
private void OnCollisionStay(Collision col)
{
// detect collision against other cars, so that we can take evasive action
if (col.rigidbody != null)
{
var otherAI = col.rigidbody.GetComponent<CarAIControl>();
if (otherAI != null)
{
// we'll take evasive action for 1 second
m_AvoidOtherCarTime = Time.time + 1;
// but who's in front?...
if (Vector3.Angle(transform.forward, otherAI.transform.position - transform.position) < 90)
{
// the other ai is in front, so it is only good manners that we ought to brake...
m_AvoidOtherCarSlowdown = 0.5f;
}
else
{
// we're in front! ain't slowing down for anybody...
m_AvoidOtherCarSlowdown = 1;
}
// both cars should take evasive action by driving along an offset from the path centre,
// away from the other car
var otherCarLocalDelta = transform.InverseTransformPoint(otherAI.transform.position);
float otherCarAngle = Mathf.Atan2(otherCarLocalDelta.x, otherCarLocalDelta.z);
m_AvoidPathOffset = m_LateralWanderDistance*-Mathf.Sign(otherCarAngle);
}
}
}
public void SetTarget(Transform target)
{
m_Target = target;
m_Driving = true;
}
}
}