Working on a AI Steering Behavior script

Hi there

I'm not sure it's the right section as I'm not putting this script in the Asset store, or at least not yet.

I started working on a script for defining AI Steering Behaviors and I thought it would be cool to share it, either for helping others and improving it.

It's quite basic, I only worked on it a couple of hours, and it's written in Javascript. At the moment it uses transforms instead of rigidbodies, may be useful to create a script for both.

The target object has a Move script attached to it. which I also used to calculate instant velocity:

Code (csharp):

1.  
2.  
3. #pragma strict
4.  
5. public var moveSpeed : int = 10;
6.  
7. var instantVelocity : Vector3;
8.  
9. function Start () {
10.     instantVelocity = Vector3.zero;
11. }
12.  
13. function Update () {
14.     var pos : Vector3 = transform.position;
15.    
16.     var horMovement = Input.GetAxis("Horizontal");
17.     var forwardMovement = Input.GetAxis("Vertical");
18.  
19.     if (horMovement) {
20.         transform.Translate(transform.right * horMovement * Time.deltaTime * moveSpeed);
21.     }
22.  
23.     if (forwardMovement) {
24.         transform.Translate(transform.forward * forwardMovement * Time.deltaTime * moveSpeed);
25.     }
26.    
27.     instantVelocity = transform.position - pos;
28. }
29.  
30.  

Then, the current AI script. Currently it has Seek, Flee, Arrive, Pursuit and Evade behaviors. The methods work, but I think some of them still need tweaking.

I think the next step is to get rid of the switch case.

Code (csharp):

1.  
2.  
3. /*
4.  
5. AI Steering Behavior Script by Attilio Carotenuto - 2012 - All Rights Reserved
6. http://www.attiliocarotenuto.com
7.  
8. */
9.  
10. #pragma strict
11.  
12. public var target : Transform;
13.  
14. public var moveSpeed : float = 6.0;
15. public var rotationSpeed : float = 1.0;
16.  
17. private var minDistance : int = 5;
18. private var safeDistance : int = 60;
19.  
20. enum AIState {Idle, Seek, Flee, Arrive, Pursuit, Evade}
21. public var currentState : AIState;
22.  
23. function Update () {
24.     switch(currentState){
25.         case AIState.Idle:
26.             break;
27.         case AIState.Seek:
28.             Seek();
29.             break;
30.         case AIState.Flee:
31.             Flee();
32.             break;
33.         case AIState.Arrive:
34.             Arrive();
35.             break;
36.         case AIState.Pursuit:
37.             Pursuit();
38.             break;
39.         case AIState.Evade:
40.             Evade();
41.             break;
42.     }
43. }
44.  
45. function Seek () : void{
46.     var direction : Vector3 = target.position - transform.position;
47.    direction.y = 0;
48.  
49.    transform.rotation = Quaternion.Slerp(transform.rotation, Quaternion.LookRotation(direction), rotationSpeed * Time.deltaTime);
50.  
51.    if(direction.magnitude > minDistance){
52.  
53.       var moveVector : Vector3 = direction.normalized * moveSpeed * Time.deltaTime;
54.  
55.       transform.position += moveVector;
56.  
57.    }
58. }
59.  
60. function Flee () : void{
61.     var direction : Vector3 = transform.position - target.position;
62.    direction.y = 0;
63.    
64.    if(direction.magnitude < safeDistance){
65.       transform.rotation = Quaternion.Slerp(transform.rotation, Quaternion.LookRotation(direction), rotationSpeed * Time.deltaTime);
66.       var moveVector : Vector3 = direction.normalized * moveSpeed * Time.deltaTime;
67.       transform.position += moveVector;
68.    }
69. }
70.  
71. function Arrive () : void{
72.     var direction : Vector3 = target.position - transform.position;
73.     direction.y = 0;
74.    
75.     var distance : float = direction.magnitude;
76.    
77.     var decelerationFactor : float = distance / 5;
78.    
79.     var speed : float = moveSpeed * decelerationFactor;
80.    
81.     transform.rotation = Quaternion.Slerp(transform.rotation, Quaternion.LookRotation(direction), rotationSpeed * Time.deltaTime);
82.  
83.     var moveVector : Vector3 = direction.normalized * Time.deltaTime * speed;
84.     transform.position += moveVector;
85. }
86.  
87. function Pursuit () : void{
88.     var iterationAhead : int = 30;
89.    
90.     var targetSpeed = target.gameObject.GetComponent(Move).instantVelocity;
91.    
92.     var targetFuturePosition : Vector3 = target.transform.position + (targetSpeed * iterationAhead);
93.    
94.     var direction : Vector3 = targetFuturePosition - transform.position;
95.     direction.y = 0;
96.  
97.    transform.rotation = Quaternion.Slerp(transform.rotation, Quaternion.LookRotation(direction), rotationSpeed * Time.deltaTime);
98.  
99.    if(direction.magnitude > minDistance){
100.  
101.       var moveVector : Vector3 = direction.normalized * moveSpeed * Time.deltaTime;
102.  
103.       transform.position += moveVector;
104.  
105.    }
106. }
107.  
108. function Evade () : void{
109.     var iterationAhead : int = 30;
110.    
111.     var targetSpeed = target.gameObject.GetComponent(Move).instantVelocity;
112.    
113.     var targetFuturePosition : Vector3 = target.position + (targetSpeed * iterationAhead);
114.    
115.     var direction : Vector3 = transform.position - targetFuturePosition;
116.     direction.y = 0;
117.  
118.    transform.rotation = Quaternion.Slerp(transform.rotation, Quaternion.LookRotation(direction), rotationSpeed * Time.deltaTime);
119.  
120.    if(direction.magnitude < safeDistance){
121.  
122.       var moveVector : Vector3 = direction.normalized * moveSpeed * Time.deltaTime;
123.  
124.       transform.position += moveVector;
125.  
126.    }
127. }
128.  
129.  

The script already works, just attach it to a game object, set a target game object and attach the Move script to it.

Looking forward for comments

 

Hey guy , good job

 

Thanks!!

 

Any update on this? )

 

This code looks like (is) an adaptation from "Programming Game AI by Example" book from Mat Buckland.

 

@Edgyr45 I don't think so - it's an implementation of the widely-used Steering Behaviours for autonomous characters described by Craig Reynolds (which is described in Buckland's book, and pretty much every other book on Game A.I.).

 

@tanoshimi you're right! thanks for the link, that's a very nice reading. My point in mentioning this was to reply to vicenterusso that "wanted an update on this". Both the book and tanoshimi's link should be next!

 

@Edgyr45 Not really an adaptation, but "Programming Game AI by Example" is where I learned about steering behaviours, so it's definitely a reference for this script

 

thanks but this code not work for me!

Code (CSharp):

1. using System.Collections;
2. using System.Collections.Generic;
3. using UnityEngine;
4.  
5. public class Move : MonoBehaviour {
6.  
7. public int moveSpeed = 10;
8. public Vector3 instantVelocity;
9. void Start () {
10. instantVelocity = Vector3.zero;
11. }
12. void Update () {
13. Vector3 pos = transform.position;
14. var horMovement = Input.GetAxis("Horizontal");
15. var forwardMovement = Input.GetAxis("Vertical");
16. if (horMovement == 1) {
17. transform.Translate(transform.right * horMovement * Time.deltaTime * moveSpeed);
18. }
19. if (forwardMovement == 1) {
20. transform.Translate(transform.forward * forwardMovement * Time.deltaTime * moveSpeed);
21. }
22. instantVelocity = transform.position - pos;
23. }
24. }
25.  

Code (CSharp):

1.  
2.  
3.  
4.  
5. using System.Collections;
6. using System.Collections.Generic;
7. using UnityEngine;
8.  
9. public class SteeringBehaviours : MonoBehaviour {
10.  
11. public Transform target;
12. public float moveSpeed = 6.0f;
13. public float rotationSpeed = 1.0f;
14. private int minDistance = 5;
15. private int safeDistance = 60;
16. public enum AIState {Idle, Seek, Flee, Arrive, Pursuit, Evade}
17. public AIState currentState;
18. void Update () {
19. switch(currentState){
20. case AIState.Idle:
21. break;
22. case AIState.Seek:
23. Seek();
24. break;
25. case AIState.Flee:
26. Flee();
27. break;
28. case AIState.Arrive:
29. Arrive();
30. break;
31. case AIState.Pursuit:
32. Pursuit();
33. break;
34. case AIState.Evade:
35. Evade();
36. break;
37. }
38. }
39. void Seek (){
40. Vector3 direction = target.position - transform.position;
41. direction.y = 0;
42. transform.rotation = Quaternion.Slerp(transform.rotation, Quaternion.LookRotation(direction), rotationSpeed * Time.deltaTime);
43. if(direction.magnitude > minDistance){
44. Vector3 moveVector = direction.normalized * moveSpeed * Time.deltaTime;
45. transform.position += moveVector;
46. }
47. }
48. void Flee () {
49. Vector3 direction = transform.position - target.position;
50. direction.y = 0;
51. if(direction.magnitude < safeDistance){
52. transform.rotation = Quaternion.Slerp(transform.rotation, Quaternion.LookRotation(direction), rotationSpeed * Time.deltaTime);
53. Vector3 moveVector = direction.normalized * moveSpeed * Time.deltaTime;
54. transform.position += moveVector;
55. }
56. }
57. void Arrive (){
58. Vector3 direction = target.position - transform.position;
59. direction.y = 0;
60. float distance = direction.magnitude;
61. float decelerationFactor = distance / 5;
62. float speed = moveSpeed * decelerationFactor;
63. transform.rotation = Quaternion.Slerp(transform.rotation, Quaternion.LookRotation(direction), rotationSpeed * Time.deltaTime);
64. Vector3 moveVector = direction.normalized * Time.deltaTime * speed;
65. transform.position += moveVector;
66. }
67. void Pursuit (){
68. int iterationAhead = 30;
69. var targetSpeed = target.gameObject.GetComponent<Move>().instantVelocity;
70. Vector3 targetFuturePosition = target.transform.position + (targetSpeed * iterationAhead);
71. Vector3 direction = targetFuturePosition - transform.position;
72. direction.y = 0;
73. transform.rotation = Quaternion.Slerp(transform.rotation, Quaternion.LookRotation(direction), rotationSpeed * Time.deltaTime);
74. if(direction.magnitude > minDistance){
75. Vector3 moveVector = direction.normalized * moveSpeed * Time.deltaTime;
76. transform.position += moveVector;
77. }
78. }
79. void Evade (){
80. int iterationAhead = 30;
81. var targetSpeed = target.gameObject.GetComponent<Move>().instantVelocity;
82. Vector3 targetFuturePosition = target.position + (targetSpeed * iterationAhead);
83. Vector3 direction = transform.position - targetFuturePosition;
84. direction.y = 0;
85. transform.rotation = Quaternion.Slerp(transform.rotation, Quaternion.LookRotation(direction), rotationSpeed * Time.deltaTime);
86. if(direction.magnitude < safeDistance){
87. Vector3 moveVector = direction.normalized * moveSpeed * Time.deltaTime;
88. transform.position += moveVector;
89. }
90. }
91. }
92.  
93.  

 

thanks but this code not work for me!

Code (CSharp):

1. using System.Collections;
2. using System.Collections.Generic;
3. using UnityEngine;
4.  
5. public class Move : MonoBehaviour {
6.  
7. public int moveSpeed = 10;
8. public Vector3 instantVelocity;
9. void Start () {
10. instantVelocity = Vector3.zero;
11. }
12. void Update () {
13. Vector3 pos = transform.position;
14. var horMovement = Input.GetAxis("Horizontal");
15. var forwardMovement = Input.GetAxis("Vertical");
16. if (horMovement == 1) {
17. transform.Translate(transform.right * horMovement * Time.deltaTime * moveSpeed);
18. }
19. if (forwardMovement == 1) {
20. transform.Translate(transform.forward * forwardMovement * Time.deltaTime * moveSpeed);
21. }
22. instantVelocity = transform.position - pos;
23. }
24. }
25.  

Code (CSharp):

1.  
2.  
3.  
4.  
5. using System.Collections;
6. using System.Collections.Generic;
7. using UnityEngine;
8.  
9. public class SteeringBehaviours : MonoBehaviour {
10.  
11. public Transform target;
12. public float moveSpeed = 6.0f;
13. public float rotationSpeed = 1.0f;
14. private int minDistance = 5;
15. private int safeDistance = 60;
16. public enum AIState {Idle, Seek, Flee, Arrive, Pursuit, Evade}
17. public AIState currentState;
18. void Update () {
19. switch(currentState){
20. case AIState.Idle:
21. break;
22. case AIState.Seek:
23. Seek();
24. break;
25. case AIState.Flee:
26. Flee();
27. break;
28. case AIState.Arrive:
29. Arrive();
30. break;
31. case AIState.Pursuit:
32. Pursuit();
33. break;
34. case AIState.Evade:
35. Evade();
36. break;
37. }
38. }
39. void Seek (){
40. Vector3 direction = target.position - transform.position;
41. direction.y = 0;
42. transform.rotation = Quaternion.Slerp(transform.rotation, Quaternion.LookRotation(direction), rotationSpeed * Time.deltaTime);
43. if(direction.magnitude > minDistance){
44. Vector3 moveVector = direction.normalized * moveSpeed * Time.deltaTime;
45. transform.position += moveVector;
46. }
47. }
48. void Flee () {
49. Vector3 direction = transform.position - target.position;
50. direction.y = 0;
51. if(direction.magnitude < safeDistance){
52. transform.rotation = Quaternion.Slerp(transform.rotation, Quaternion.LookRotation(direction), rotationSpeed * Time.deltaTime);
53. Vector3 moveVector = direction.normalized * moveSpeed * Time.deltaTime;
54. transform.position += moveVector;
55. }
56. }
57. void Arrive (){
58. Vector3 direction = target.position - transform.position;
59. direction.y = 0;
60. float distance = direction.magnitude;
61. float decelerationFactor = distance / 5;
62. float speed = moveSpeed * decelerationFactor;
63. transform.rotation = Quaternion.Slerp(transform.rotation, Quaternion.LookRotation(direction), rotationSpeed * Time.deltaTime);
64. Vector3 moveVector = direction.normalized * Time.deltaTime * speed;
65. transform.position += moveVector;
66. }
67. void Pursuit (){
68. int iterationAhead = 30;
69. var targetSpeed = target.gameObject.GetComponent<Move>().instantVelocity;
70. Vector3 targetFuturePosition = target.transform.position + (targetSpeed * iterationAhead);
71. Vector3 direction = targetFuturePosition - transform.position;
72. direction.y = 0;
73. transform.rotation = Quaternion.Slerp(transform.rotation, Quaternion.LookRotation(direction), rotationSpeed * Time.deltaTime);
74. if(direction.magnitude > minDistance){
75. Vector3 moveVector = direction.normalized * moveSpeed * Time.deltaTime;
76. transform.position += moveVector;
77. }
78. }
79. void Evade (){
80. int iterationAhead = 30;
81. var targetSpeed = target.gameObject.GetComponent<Move>().instantVelocity;
82. Vector3 targetFuturePosition = target.position + (targetSpeed * iterationAhead);
83. Vector3 direction = transform.position - targetFuturePosition;
84. direction.y = 0;
85. transform.rotation = Quaternion.Slerp(transform.rotation, Quaternion.LookRotation(direction), rotationSpeed * Time.deltaTime);
86. if(direction.magnitude < safeDistance){
87. Vector3 moveVector = direction.normalized * moveSpeed * Time.deltaTime;
88. transform.position += moveVector;
89. }
90. }
91. }
92.  
93.  

 

thanks but this code not work for me!

Code (CSharp):

1. using System.Collections;
2. using System.Collections.Generic;
3. using UnityEngine;
4.  
5. public class Move : MonoBehaviour {
6.  
7. public int moveSpeed = 10;
8. public Vector3 instantVelocity;
9. void Start () {
10. instantVelocity = Vector3.zero;
11. }
12. void Update () {
13. Vector3 pos = transform.position;
14. var horMovement = Input.GetAxis("Horizontal");
15. var forwardMovement = Input.GetAxis("Vertical");
16. if (horMovement == 1) {
17. transform.Translate(transform.right * horMovement * Time.deltaTime * moveSpeed);
18. }
19. if (forwardMovement == 1) {
20. transform.Translate(transform.forward * forwardMovement * Time.deltaTime * moveSpeed);
21. }
22. instantVelocity = transform.position - pos;
23. }
24. }
25.  

Code (CSharp):

1.  
2.  
3.  
4.  
5. using System.Collections;
6. using System.Collections.Generic;
7. using UnityEngine;
8.  
9. public class SteeringBehaviours : MonoBehaviour {
10.  
11. public Transform target;
12. public float moveSpeed = 6.0f;
13. public float rotationSpeed = 1.0f;
14. private int minDistance = 5;
15. private int safeDistance = 60;
16. public enum AIState {Idle, Seek, Flee, Arrive, Pursuit, Evade}
17. public AIState currentState;
18. void Update () {
19. switch(currentState){
20. case AIState.Idle:
21. break;
22. case AIState.Seek:
23. Seek();
24. break;
25. case AIState.Flee:
26. Flee();
27. break;
28. case AIState.Arrive:
29. Arrive();
30. break;
31. case AIState.Pursuit:
32. Pursuit();
33. break;
34. case AIState.Evade:
35. Evade();
36. break;
37. }
38. }
39. void Seek (){
40. Vector3 direction = target.position - transform.position;
41. direction.y = 0;
42. transform.rotation = Quaternion.Slerp(transform.rotation, Quaternion.LookRotation(direction), rotationSpeed * Time.deltaTime);
43. if(direction.magnitude > minDistance){
44. Vector3 moveVector = direction.normalized * moveSpeed * Time.deltaTime;
45. transform.position += moveVector;
46. }
47. }
48. void Flee () {
49. Vector3 direction = transform.position - target.position;
50. direction.y = 0;
51. if(direction.magnitude < safeDistance){
52. transform.rotation = Quaternion.Slerp(transform.rotation, Quaternion.LookRotation(direction), rotationSpeed * Time.deltaTime);
53. Vector3 moveVector = direction.normalized * moveSpeed * Time.deltaTime;
54. transform.position += moveVector;
55. }
56. }
57. void Arrive (){
58. Vector3 direction = target.position - transform.position;
59. direction.y = 0;
60. float distance = direction.magnitude;
61. float decelerationFactor = distance / 5;
62. float speed = moveSpeed * decelerationFactor;
63. transform.rotation = Quaternion.Slerp(transform.rotation, Quaternion.LookRotation(direction), rotationSpeed * Time.deltaTime);
64. Vector3 moveVector = direction.normalized * Time.deltaTime * speed;
65. transform.position += moveVector;
66. }
67. void Pursuit (){
68. int iterationAhead = 30;
69. var targetSpeed = target.gameObject.GetComponent<Move>().instantVelocity;
70. Vector3 targetFuturePosition = target.transform.position + (targetSpeed * iterationAhead);
71. Vector3 direction = targetFuturePosition - transform.position;
72. direction.y = 0;
73. transform.rotation = Quaternion.Slerp(transform.rotation, Quaternion.LookRotation(direction), rotationSpeed * Time.deltaTime);
74. if(direction.magnitude > minDistance){
75. Vector3 moveVector = direction.normalized * moveSpeed * Time.deltaTime;
76. transform.position += moveVector;
77. }
78. }
79. void Evade (){
80. int iterationAhead = 30;
81. var targetSpeed = target.gameObject.GetComponent<Move>().instantVelocity;
82. Vector3 targetFuturePosition = target.position + (targetSpeed * iterationAhead);
83. Vector3 direction = transform.position - targetFuturePosition;
84. direction.y = 0;
85. transform.rotation = Quaternion.Slerp(transform.rotation, Quaternion.LookRotation(direction), rotationSpeed * Time.deltaTime);
86. if(direction.magnitude < safeDistance){
87. Vector3 moveVector = direction.normalized * moveSpeed * Time.deltaTime;
88. transform.position += moveVector;
89. }
90. }
91. }
92.  
93.