Make a enemy strafe (zigzag) in one direction

Hello, i am new to c# programming. I have tried to write a script for a enemy to strafe(zigzag) down towards the bottom of the screen. ( top down view ) and i cant get it right.
And yeah i have tried the
Mathf.PingPong method but i dosent realy do what i need it to do. Since i want it to be more random then that.

Do you have any suggestions?

Thanks.

This is my code:

private float rangeX = 2f;
private float speed = 3;


// Update is called once per frame
void Update()
{

transform.Translate(Vector3.forward * Time.deltaTime * speed);
transform.Translate(Vector3.left * Time.deltaTime * speed);

if (transform.position.x < -rangeX)

{
transform.Translate(Vector3.left * Time.deltaTime * speed);
}
if (transform.position.x > rangeX)

{
transform.Translate(Vector3.right * Time.deltaTime * speed);
}

 

Usually for enemies you would use a timer and some values to cause it to behave differently during those time intervals.

Lets say he decides "Hey, I'm gonna strafe!" He would pick an amount of time (or distance) to move left/right, and then do that while he is counting down those timers to return to standing still.

Also, be aware of the difference between

Vector3.right

and

transform.right

: the former is in world space (does not change based on the player's heading), and the latter is in the coordinate space of the transform itself. If your transform is rotated to

Quaternion.identity

, only then are these properties identical. Same goes for

transform.up

and

transform.forward

.

Note also there is no

transform.back

: you just negate

transform.forward

. Same goes for

transform.left

and

transform.down

.

 

You probably already transforming down then to the left in your first two lines in Update() unless you want to move diagonally? The rest of your code seems right without testing.

Code (CSharp):

1. private float rangeX = 2f;
2. private float speed = 3;
3.  
4.  
5. // Update is called once per frame
6. void Update()
7. {
8.  
9. transform.Translate(Vector3.forward * Time.deltaTime * speed);
10. // transform.Translate(Vector3.left * Time.deltaTime * speed); // delete this line if you want to go straight down
11.  
12. if (transform.position.x < -rangeX)
13.  
14. {
15. transform.Translate(Vector3.left * Time.deltaTime * speed);
16. }
17. if (transform.position.x > rangeX)
18.  
19. {
20. transform.Translate(Vector3.right * Time.deltaTime * speed);
21. }

 

Hey, thank you for you answer. Hmm it where kind of hard for me to explain this. But I have made a GIF to try to explain what I want to achieve!

On the top red line the enemy's spawn random and "strafe" downward, I want them to stay at the same rotation like illustrated in the GIF. The green box is the enemy. And since they spawn at random X axis I can't calculate the time at one direction. And it takes away the inbuilt ping pong method. And the blue rectangle is the screen, so I have no walls.

Cheers!

 

Your motion GIF is pure lateral bounce. Move in the direction until you reach the lateral limit, then negate the .x component of your motion, lather rinse, repeat. Use a

Vector3

or

Vector2

for your motion and it becomes as easy as directly adding it to the

transform.position

property.

 

Here it is. Vector3.Left goes (-1,0,0) x, y, z from article below. Same with .Forward and .Right.
So you will have to check the coordinates and see which one fits the screen.

Code (CSharp):

1. private float rangeX = .5f;
2. private float speed = 4;
3.  
4.  
5. // Update is called once per frame
6. void Update()
7. {
8.  
9. transform.Translate(Vector3.(1,0,0) * Time.deltaTime * speed);
10.  
11. if (transform.position.x < -rangeX)
12.  
13. {
14. transform.Translate(Vector3.(-8,0,0) * Time.deltaTime * speed);
15. }
16. if (transform.position.x > rangeX)
17.  
18. {
19. transform.Translate(Vector3.(8,0,0) * Time.deltaTime * speed);
20. }

https://docs.unity3d.com/ScriptReference/Vector3-left.html

Hope this works! Good Luck!

 

I really can't get this to work. It does not go the other way when it gets to the limit?

It where really easy when I made the prototype in Godot Engine. I wish I could just use that code or translate it well. The only option I've found is to use RigidBody and add forces, but then the enemy start colliding with each other and gain speed at random places.

godot code:
func _process(_delta: float) -> void:
if get_position().x <= 0+16:
velocity.x = abs(velocity.x)
if get_position().x >= get_viewport_rect().size.x-16:
velocity.x = -abs(velocity.x)

 

Okay, here's some direct steps:

1. make a blank game object that represents the left side
2. make another one to represent the right side
3. put a script on your moving object that does the following:

- has a Vector3 containing its starting velocity
- has a Vector3 containing its current velocity
- contains two public fields into which you can drag the left and right limit objects for later use

In

Start()

:
- set current velocity equal to initial

Now in

Update()

:

- move the transform.position by the current velocity (make sure to multiply by Time.deltaTime)

- check if the transform.position.x is less than the transform.position.x of the left bounds
---- if it is, then set the .x of your current velocity equal to the

Mathf.Abs()

of what it was before

- check if the transform.position.x is greater than the transform.position.x of the right bounds
---- if it is, then set the .x of your current velocity equal to the

-Mathf.Abs()

of what it was before

If you give it a down and to the right (or down and to the left) initial velocity, that will cause it to ping-pong back and forth the way your GIF shows.

 

I believe I fixed the if statement so that the gameobject can move within the the screen. You may have to play with the numbers (8). Then, the y direction was missing because you want it to move top to down if not your direction put it (0, -1, 0), and I placed that there. Hope it works!

Code (CSharp):

1. private float rangeX = .5f;
2. rangeXDiagonal = 9f;
3. private float speed = 4;
4.  
5. // Update is called once per frame
6. void Update()
7. {
8. transform.Translate(Vector3.(0,1,0) * Time.deltaTime * speed);
9. if (transform.position.x < rangeXDiagonal)
10. {
11. transform.Translate(Vector3.(-8,0,0) * Time.deltaTime * speed);
12. }
13. if (transform.position.x  > rangeXDiagonal)
14. {
15. transform.Translate(Vector3.(8,0,0) * Time.deltaTime * speed);
16. }

 

Thanks for the in-depth description!
But I must have a brain block, can't get this to work! I must have gotten some of the fundamental skills wrong.
Do you know any reference code I could study? I don't understand how to set initial velocity without a RigidBody.

I have manage to do a lot more complex things without any help -.-

I am sorry, but thanks again for your time trying to explain this to me.

 

What I am mentioning above is for you to do your own movement, either without a Rigidbody or with an .isKinematic one, which means Unity Physics will NOT be moving the object, YOU will be moving it in your script.

If you look at the code pattern by @ashkanaral above, it's very close to what I'm suggesting you try. His line 8 is the part that moves the object by the current velocity times Time.deltaTime.

Read my post again; it's virtually pseudocode of exactly the steps that must happen.

 

That code is not valid it would be something like.

transform.Translate(0, 0, 1 * Time.deltaTime * speed);

But the problem reality comes down to how to change the speed. If its in the update method before the if. it will still keep on pushing it in that direction. so lets say I put

transform.Translate(1, 0, 0, * Time.deltaTime * speed);
If (transform.position.x > 1)
transform.Translate(-1, 0, 0 * time deltaTime * speed);

"this will make the object stand still at 2x)
as soon as it not > 2x it will start moving towards 2x again.
So I would need another function I guess then transform.Translate.

A function that sets the objects transform or such in a direction, and not stop until it told to.
I am thinking of a bool. like if right is true keep pushing this direction
edit And WOW I tried that out. it actually worked!

This is my code:

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class CleverEnemy : MonoBehaviour
{
public bool isPlayerMovingRight = true;
public float strafeSpeed = 1f;
public float forwardThrust = 0.5f;
public float boundary = 5f;
// Start is called before the first frame update
void Start()
{

}

// Update is called once per frame
void Update()
{
transform.Translate(Vector3.forward * Time.deltaTime * forwardThrust);

if (transform.position.x > boundary)
isPlayerMovingRight = false;
if (transform.position.x < -boundary)
isPlayerMovingRight = true;

if (isPlayerMovingRight == true)
{
transform.Translate(Vector3.right * Time.deltaTime * strafeSpeed);
}
if (isPlayerMovingRight == false)
{
transform.Translate(Vector3.left * Time.deltaTime * strafeSpeed);
}
}
}

works like a charm.

Thanks everyone that took their time to help me!

 

Hi,

I'd just like to say thanks for posting this code. I have been looking for a way to create a zig zag in my enemies and was struggling. After seeing this I managed to slightly modify it for my game. I was so close to this but couldn't quite get it to work.

You are a star.