Yes, I read through about 30 different similar titles before posting this. However, there wasn't anything relevant to what I need. I'm trying to set my camera's Y-axis to follow the player as it moves through the level; however, I don't want the camera to move up and down whilst jumping so I follow the camera's transform.position.y and NOT the player's.
void Pjump()
{
if (Input.GetKeyDown(KeyCode.Space) && onFloor==true
|| Input.GetKeyDown(KeyCode.W) && onFloor==true)
{
player.velocity = new Vector2(0, jump);
onFloor = false;
isJumping = true; // Static Variable to pass onto CamFollow script
}
}
isJumping is set false inside an OnCollisionEnter2d() and called inside of a FixedUpdate().
Now for the CamFollow script
using System.Collections;
using System.Collections.Generic;
using UnityEngine;
public class CamFollow : MonoBehaviour
{
private GameObject p1;
private bool isFollow;
[Header("Camera Offset Values")]
[SerializeField]
private float xOff;
[SerializeField]
private float yOff;
void Start()
{
p1 = GameObject.FindWithTag("Player");
isFollow = true;
}
void FixedUpdate()
{
if (isFollow)
{
if (Pmove.isJumping == false) // This code works fine
{
transform.position = new Vector3(p1.transform.position.x + xOff, p1.transform.position.y + yOff,
transform.position.z);
}
if(Pmove.isJumping == true) // This is where the problem is: Y-Axis
{
transform.position = new Vector3(p1.transform.position.x + xOff, transform.position.y + yOff,
transform.position.z);
}
}
}
}
When the player jumps, the player and all non-UI objects vanish until the player touches the ground.
Related
Context
So I'm making a clone of Crossy Roads where the camera follows the player. It does some linear interpolation (Lerp) after moving, and the camera starts moving away from the player in the positive direction (x-axis until camera reaches to a certain range where player is not visible enough). Things I have tried is by flagging it, but I think I'm doing it wrong.
Problem
I have done my camera movements accordingly, but I am having an issue where the conditions are not properly met. I'm get the offset camera after not moving, but it does not the Lerp, and vice-versa. I want both to happen after a certain condition after the game starts. When the player moves, the camera follows it in Lerp. However, once the player is "Idle", its still Lerping. I want the camera to continue by itself and at the same time focus at the player's object.
Example
Camera with Lerp, but not moving away from the player
Camera moving away, but not following player with lerp
Code
CameraController.cs
using System.Collections;
using System.Collections.Generic;
using UnityEngine;
/*
** Camera following player (Smoothing and angle): https://youtu.be/4HpC--2iowE
** Maximo: https://www.youtube.com/watch?v=bXNFxQpp2qk&ab_channel=iHeartGameDev
** Moving character relative to camera: https://forum.unity.com/threads/moving-character-relative-to-camera.383086/
** Camera follow v2: https://youtu.be/Jpqt2gRHXtc?list=PLq_nO-RwB516fNlRBce0GbtJSfysAjOgU
*/
public class CameraController : MonoBehaviour
{
public GameObject player;
public PlayerControl playerControlScript;
private Vector3 newCameraPos;
public bool stillIdle;
void Start()
{
stillIdle = false;
PlayerControl playerControlScript = GetComponent<PlayerControl>();
}
void LateUpdate()
{
player = GameObject.FindGameObjectWithTag("Player");
if (playerControlScript.GetfirstInput()) //True
{
stillIdle = true;
newCameraPos = Vector3.Lerp(transform.position, playerControlScript.transform.position, Time.deltaTime);
transform.position = new Vector3(newCameraPos.x, 1, newCameraPos.z);
}
if (stillIdle)
transform.position = new Vector3(transform.position.x + 0.69f * Time.deltaTime, transform.position.y, transform.position.z); //Moving camera away effect
}
}
PlayerControl.cs
public class PlayerControl : MonoBehaviour
{
bool firstInput;
Vector3 startPos;
Vector3 endPos;
public bool GetfirstInput() //I was learning how to have a Get function while my member was private from another script file
{
return firstInput;
}
void Update()
{
if (Input.GetButtonDown("up") || Input.GetButtonDown("left") || Input.GetButtonDown("right") || Input.GetButtonDown("down"))
{
//if game starts
{
//Other variables being initialized here
firstInput = true;
}
}
}
}
Hierarchy/Inspector
Main Camera
Player Object
Some help would be appreciate it. I feel I have been staring at this problem and I bet it is something minimal and small from just thinking it.
Let me know if you need clarifications. I'm happy to edit and answer them for everyone
If player in your game does not change, you don't have to find the player reference in each LateUpdate().
I notice that once stillIdle is set true, it never goes back to false, is this your intention to do that?
You call Lerp when playerControlScript.GetfirstInput() is true, so maybe we need to look at its implementation. Maybe it turns true in some conditions you do not intend it to.
Maybe Try this
public class PlayerControl : MonoBehaviour
{
private bool _hasFireFirstInput = false;
private bool _isIdle = true;
public bool IsIdle => _isIdle;
public bool HasFireFirstInput => _hasFireFirstInput;
private void Update()
{
if (Input.GetButton("Horizontal") || Input.GetButton("Vertical"))
{
_hasFireFirstInput = true;
_isIdle = false;
Vector3 pos = transform.position;
pos = new Vector3(pos.x, pos.y, pos.z + .2f * Time.deltaTime);
transform.position = pos;
}
else
{
_isIdle = true;
}
}
}
I use Input.GetButton() rather than Input.GetButtonDown(), since the later only return true at the frame the button is pressed, meaning that if i long-press the button, it will return false after the next frame.
public class CameraController : MonoBehaviour
{
[SerializeField] PlayerControl _playerControlScript;
[SerializeField] Vector3 _offset;
[SerializeField] float _lerpSpeed;
bool _iskeepLerping = false;
float _lerpVal = 0f;
private void LateUpdate()
{
if (!_playerControlScript.HasFireFirstInput)
{
return;
}
if (_playerControlScript.IsIdle)
{
MoveAway();
}
else
{
Lerp();
}
}
private void MoveAway()
{
_iskeepLerping = false;
transform.position = new Vector3(transform.position.x + 0.69f * Time.deltaTime, transform.position.y, transform.position.z);
}
private void Lerp()
{
if (!_iskeepLerping)
{
_lerpVal = 0f;
}
Vector3 newCameraPos = Vector3.Lerp(transform.position, _playerControlScript.transform.position + _offset, _lerpVal);
transform.position = newCameraPos;
_lerpVal += _lerpSpeed * Time.deltaTime;
_iskeepLerping = true;
}
}
I'm making a 2D game where the player moves left and right while dodging falling objects, I put triggers so it doesn't leave the screen but sometimes when it collides with these triggers it passes this collider. I sent an image of the colliders, the Player inspector and also a collider.
Here my Player code
using System.Collections;
using System.Collections.Generic;
using UnityEngine;
public class Ball : MonoBehaviour
{
public bool isRight;
public float speed;
public Transform pointR;
public Transform pointL;
Rigidbody2D rb;
private SpriteRenderer sprite;
private float maxSpeed;
[Header("PowerUps")]
public float force;
// Start is called before the first frame update
void Start()
{
rb = GetComponent<Rigidbody2D>();
sprite = GetComponent<SpriteRenderer>();
maxSpeed = 600f;
}
void Update()
{
if(Input.GetMouseButtonDown(0))
{
isRight = !isRight;
}
}
void FixedUpdate()
{
if(isRight)
{
rb.velocity = new Vector2(speed, 0);
rb.AddForce(rb.velocity,ForceMode2D.Force );
sprite.flipX = true;
if(rb.velocity.x >= maxSpeed)
{
rb.velocity = new Vector2(maxSpeed, 0);
}
}
else
{
rb.velocity = new Vector2(-speed, 0 );
rb.AddForce(rb.velocity, ForceMode2D.Force );
sprite.flipX = false;
}
}
void OnTriggerEnter2D(Collider2D collider)
{
if(collider.gameObject.tag =="ColliderL")
{
isRight = !isRight;
}
if(collider.gameObject.tag == "ColliderR")
{
isRight = !isRight;
}
// For PowerUps
if(collider.gameObject.tag == "SpeedUp")
{
StartCoroutine(Seconds());
}
}
IEnumerator Seconds()
{
rb.AddForce(rb.velocity * force);
yield return new WaitForSeconds(5f);
rb.AddForce(rb.velocity * -force);
}
}
I would ideally need to see your scene setup to further pinpoint your mistakes. But these are a few common mistakes that are made:
Tags are case-sensitive. Also, make sure to assign them.
Your collider on one of the object is not 2D; There is Collider, then there is Collider2D.
Your collider is not marked as trigger.
Though there are a few non-related problems with your setup:
rb.velocity.collider doesn't exist. You are looking for rb.velocity.
Ideally you want to set physics changes (velocity, in your case) to FixedUpdate() instead.
If you do want to get colliders from RigidBody, use GetAttachedColliders.
Assuming you are setting up a border which the player can never pass through, you should use a full collider instead of a trigger. This uses OnCollisionEnter2D.
new Vector2(speed, 0* Time.deltaTime);
0 * Time.deltaTime does nothing, since you are multiplying by 0.
What you are looking for is probably new Vector2(speed * Time.deltaTime, 0);. But you don't need to multiply the speed by deltaTime since you are not moving the ball manually via it's Transform.
rb.velocity = new Vector2(speed, 0); should be your result.
I have a physics enabled sphere in my scene and a character that i can move around using WASD. now what i want is that as soon as player hits the ball it should not be physics enabled anymore and move along with player as like the player is holding it in the hands.
What i have tried so far:
i was able to do it but not at all perfect how i want it to be. i tried OnCollisionEnter to detect the collision, i made the sphere a child of the player, i used isKinematic = true as soon as collision is detected and i used Vector3.MoveTowards for the object to follow the position as the player.
I have attached two reference videos below
Reference Clip(The style i am aiming for):https://www.youtube.com/watch?v=fi-GB0RwLr0
MyVersion(This is what i am able to do):https://www.youtube.com/watch?v=JtV11KHY4pU
overall, if you watch the clips you can see how my version is very rigid, stucky, buggy, not so light weight feeling at all. Cut me a slack as well if i did anything way wrong, i started unity like just in the previous month.
This is my Player script through which i am controlling it all
using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.SceneManagement;
public class Player : MonoBehaviour
{
public float MoveSpeed;
[SerializeField]private Rigidbody playerRig;
[SerializeField] private Rigidbody ballRig;
[SerializeField] private GameObject Ball;
[SerializeField] private GameObject heldObj;
private bool isTouching = false;
private Vector3 offset = new Vector3(0, 1, 3);
private Vector3 force;
public float jump;
private bool isGrounded = true;
private void Start()
{
Ball = GameObject.FindGameObjectWithTag("Ball");
ballRig.GetComponent<Rigidbody>();
playerRig.GetComponent<Rigidbody>();
}
void Update()
{
float x = Input.GetAxis("Horizontal");
float z = Input.GetAxis("Vertical");
playerRig.velocity = new Vector3(x*MoveSpeed, playerRig.velocity.y,z*MoveSpeed);
Vector3 vel = playerRig.velocity;
vel.y = 0;
if (vel.x != 0 || vel.z != 0)
{
transform.forward = vel;
}
if(transform.position.y < -10)
{
GameOver();
}
ReleaseTheBall();
if (isTouching == true)
{
ballRig.transform.position = Vector3.MoveTowards(ballRig.transform.position, playerRig.transform.position, 5f);
}
}
void Jump()
{
force = new Vector3(0, jump, 0);
if (Input.GetKeyDown(KeyCode.Space) && isGrounded == true)
{
isGrounded = false;
playerRig.AddForce(force, ForceMode.Impulse);
}
}
private void OnCollisionEnter(Collision collision)
{
if(collision.gameObject.tag == "Ball" && heldObj == null)
{
ballRig.isKinematic = true;
// ballRig.constraints = RigidbodyConstraints.FreezeRotation;
ballRig.transform.parent = playerRig.transform;
isTouching = true;
Debug.Log(" BALL PICKED UP AND MOVING ");
heldObj = Ball;
}
}
public void ReleaseTheBall()
{
if (Input.GetKeyDown(KeyCode.Space) && heldObj != null)
{
isTouching = false;
heldObj = null;
ballRig.transform.parent = null;
//ballRig.constraints = RigidbodyConstraints.None;
ballRig.isKinematic = false;
//Vector3 forceDirection = new Vector3(playerRig.transform.position.x, 0, playerRig.transform.position.z);
Vector3 rotationDirection = new Vector3(playerRig.transform.rotation.x, playerRig.transform.rotation.y, playerRig.transform.rotation.z);
ballRig.AddForce(new Vector3(transform.position.x,0,transform.position.z) * 5, ForceMode.Impulse);
ballRig.AddTorque(rotationDirection * 1);
Debug.Log("BALL RELEASED");
}
}
public void GameOver()
{
SceneManager.LoadScene(SceneManager.GetActiveScene().buildIndex);
}
}
i know there could be some very inefficient lines of code here, feel free to call out those lines as well.
So, basically what i want is that i want my player to pick up the ball as soon as it hits it and the ball should move exactly like player as if he is holding the ball in his hands and when i hit the spacebar i want the ball to be released into the direction i am looking(this part is also very tricky for me), what i am trying to do is i want to do exactly like in the refrence clip. Thanks a lot in advance.
one more thing, when i stop pressing any key to move(WASD), my player transform keeps changing values up and down and it slightly starts moving. i mean when i dont press any key, it still kinda moves.
First of all, you have indeed quite a lot of lines that aren't useful in here and that could be optimized.
Anyway, I hope this will do what you want it to do:
using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.SceneManagement;
[RequireComponent(typeof(Rigidbody))]
public class Player : MonoBehaviour {
[Header("Movement Setup")]
[Tooltip("Translation speed in m/s")]
[SerializeField] float _TranslationSpeed;
[Tooltip("Rotation speed in °/s")]
[SerializeField] float _RotationSpeed;
[Tooltip("Interpolation speed [0;1]")]
[SerializeField] float _InterpolationSpeed;
[Tooltip("Strength for jumps")]
[SerializeField] float _JumpingStrength;
[Tooltip("Strength for shoots")]
[SerializeField] float _ShootingStrength;
[Header("Other Settings")]
[Tooltip("Where the helded item will be placed")]
[SerializeField] Transform _ContactPoint;
[Tooltip("Which layers should be considered as ground")]
[SerializeField] LayerMask _GroundLayer;
// The player's rigid body
Rigidbody _Rigidbody;
// Is the player on the ground
bool _IsGrounded;
// Rigidbody of what's the player is helding. Null if the player isn't holding anything
Rigidbody _HeldedItemRigidbody;
// Getter to _IsGrounded, return true if the player is grounded
public bool IsGrounded { get { return _IsGrounded; } }
private void Start() {
_Rigidbody = GetComponent<Rigidbody>(); // The player's rigidbody could be serialized
}
void FixedUpdate() {
float horizontalInput, verticalInput;
// Getting axis
horizontalInput = Input.GetAxis("Horizontal");
verticalInput = Input.GetAxis("Vertical");
// Moving toward the x
Vector3 moveVect = transform.forward * _TranslationSpeed * Time.fixedDeltaTime * verticalInput;
_Rigidbody.MovePosition(_Rigidbody.position + moveVect);
// Rotating the player based on the horizontal input
float rotAngle = horizontalInput * _RotationSpeed * Time.fixedDeltaTime;
Quaternion qRot = Quaternion.AngleAxis(rotAngle, transform.up);
Quaternion qRotUpRight = Quaternion.FromToRotation(transform.up, Vector3.up);
Quaternion qOrientationUpRightTarget = qRotUpRight * _Rigidbody.rotation;
Quaternion qNewUpRightOrientation = Quaternion.Slerp(_Rigidbody.rotation, qOrientationUpRightTarget, Time.fixedDeltaTime * _InterpolationSpeed); // We're using a slerp for a smooth movement
_Rigidbody.MoveRotation(qRot * qNewUpRightOrientation);
// This prevents the player from falling/keep moving if there is no input
if (_IsGrounded) _Rigidbody.velocity = Vector3.zero;
_Rigidbody.angularVelocity = Vector3.zero;
if (transform.position.y < -10) GameOver();
if (Input.GetKey(KeyCode.Mouse0) && _HeldedItemRigidbody != null) ShootTheBall();
if (!_IsGrounded) return; // What's below this won't be executed while jumping
if (Input.GetKey(KeyCode.Space)) Jump();
}
void Jump() {
_IsGrounded = false;
_Rigidbody.AddForce(_JumpingStrength * transform.up, ForceMode.Impulse);
}
private void OnCollisionEnter(Collision collision) {
// Checking if the player encountered a ground object
if ((_GroundLayer & (1 << collision.gameObject.layer)) > 0) _IsGrounded = true;
if (collision.gameObject.tag == "Ball") { // this can be improved as tags are error prone
// Setting the item position to contact point
collision.gameObject.transform.position = _ContactPoint.position;
// Getting the rigidbody
_HeldedItemRigidbody = collision.gameObject.GetComponent<Rigidbody>();
// Setting the parent
_HeldedItemRigidbody.transform.parent = transform;
// Setting the body to be kinematic
_HeldedItemRigidbody.isKinematic = true;
// Stopping any movement or rotation
_HeldedItemRigidbody.velocity = Vector3.zero;
_HeldedItemRigidbody.angularVelocity = Vector3.zero;
}
}
public void ShootTheBall() {
// Reverting what's done in OnCollisionEnter
_HeldedItemRigidbody.transform.parent = null;
_HeldedItemRigidbody.isKinematic = false;
// Adding force for the shoot
_HeldedItemRigidbody.AddForce(transform.forward * _ShootingStrength, ForceMode.Impulse);
// Resetting helding item to null
_HeldedItemRigidbody = null;
}
public void GameOver() {
SceneManager.LoadScene(SceneManager.GetActiveScene().buildIndex);
}
}
You have to add a layer, and set the ground to this new layer.
Set up the variable as you like, don't hesitate to mess up with it a little bit to find what suits you (and don't forget to set up the player's mass (in rigidbody) as well!!)
Exemple of setup for the player script
Last things, you have to add an empty game object to your player which will be where the ball will be placed. I know it's a little bit dirty but place it a bit far from the player (more than the ball's radius) or it will bug. We could do something programatically to fix the ball at a spot and adapt this spot to the ball's radius.
This is an example of player
As you can see, I have the empty "player" gameobject which has the rigidbody, the collider and the player script.
The GFX item which is just the capsule.
If you don't know about this: the player game object is actually on the floor (at the player's feet) so it's better for movements. If you do this, don't forget to adjust the player's capsule collider to fit the GFX.
I also have the contact point.
Forget about the nose stuff, it's just a way to see where the player is facing when you just have a capsule.
If you have any question, feel free to ask.
Im working on a first person shooter. I have an aim function, which puts the pistol right in front of the camera, to make it look like your holding it in front of you. Im trying to make it so the pistol will also rotate with the camera on the Z axis, so that way the pistol wont stay still, because that looks odd and gets in the way. To do this, I tried this:
GPR.gun.transform.rotation = Quaternion.Euler(0, 0, plrCam.transform.rotation.z);, however this ends up rotating the gun very slightly around the z axis, and mainly rotating it around the y axis whenever I move my camera. I am a beginner programmer in Unity so please try to make answers more digestible to beginners so I can understand it. Here is my full script:
using System.Collections.Generic;
using UnityEngine;
public class PistolFire : MonoBehaviour
{
//Gun Properties
public float range = 50f;
public float damage = 10f;
//Sensitivity decrease for looking down the sights
public float downSights = 5f;
//Other vars
private playerGunControls playerGun;
private GameObject plrCam;
private Camera fpsCam;
private ParticleSystem muzzleFlash;
private GameObject impactEffect;
private bool aimed = false;
private GameObject aimPos;
private GunPickupRaycast GPR;
private GameObject handPos;
private GameObject Player;
// Start is called before the first frame update
void Start()
{
//Getting objects because gun is instantiated, so this is necessary
plrCam = GameObject.Find("Player Camera");
playerGun = plrCam.GetComponent<playerGunControls>();
fpsCam = plrCam.GetComponent<Camera>();
muzzleFlash = GetComponentInChildren<ParticleSystem>();
impactEffect = GameObject.Find("Impact Effect");
aimPos = GameObject.Find("aimPos");
GPR = plrCam.GetComponent<GunPickupRaycast>();
handPos = GameObject.Find("Hand Pos");
Player = GameObject.Find("Player");
}
// Update is called once per frame
void Update()
{
//Check for shoot button down
if (Input.GetButtonDown("Fire1"))
{
if (playerGun.holding == "Pistol")
{
Shoot();
}
}
//Check if aim button down
if (Input.GetButton("Fire2"))
{
if (playerGun.holding == "Pistol")
{
Aim();
}
}
//Check if no longer aiming to reset to normal
if (aimed == true && !(Input.GetButton("Fire2")))
{
Unaim();
}
}
void Shoot()
{
muzzleFlash.Play();
RaycastHit hit;
if(Physics.Raycast(plrCam.transform.position, plrCam.transform.forward, out hit, range))
{
Debug.Log(hit.transform.name);
Health health = hit.transform.GetComponent<Health>();
if (health != null)
{
health.TakeDamage(damage);
}
//Instantiate the Impact Effect
GameObject IE = Instantiate(impactEffect, hit.point, Quaternion.identity);
Destroy(IE, 1.5f);
}
}
void Aim()
{
aimed = true;
Debug.Log("Aiming");
GPR.gun.transform.position = aimPos.transform.position;
GPR.gun.transform.rotation = Quaternion.Euler(0, 0, plrCam.transform.rotation.z);
}
void Unaim()
{
GPR.gun.transform.position = handPos.transform.position;
Debug.Log("No longer aiming");
aimed = false;
}
}
I fixed my problem by making the gun a child of my camera instead of a child of my player.
So i made a little side scroller that uses a prefab to spawn bullets.
My problem is that it only shoots to one side... the Right.
I need it to fire to the left as well. I've already made a variable to see if the player is looking to the right or left.
I've tried to put the Speed to -20 and i've tried to rotate it 180 degrees on it's Z axis. I tested if the bullet script even picked up the change from the player movement script and it does.
Player Movement script
using System.Collections;
using System.Collections.Generic;
using UnityEngine;
public class PlayerMovement : MonoBehaviour
{
public GameObject bullet;
private Rigidbody2D myRigidbody;
private float speed = 15;
private bool facingRight;
private bool ground = false;
private float jump = 23;
// Start is called before the first frame update
void Start()
{
facingRight = true;
myRigidbody = GetComponent<Rigidbody2D>();
}
// Update is called once per frame
void FixedUpdate()
{
float horizontal = Input.GetAxis("Horizontal");
Movement(horizontal);
Flip(horizontal);
if (Input.GetKey("w"))
{
if (ground)
{
GetComponent<Rigidbody2D>().velocity = new Vector2(GetComponent<Rigidbody2D>().velocity.x, jump);
}
}
if(facingRight == false)
{
bullet.GetComponent<bullet>().left = true;
}
if (facingRight == true)
{
bullet.GetComponent<bullet>().left = false;
}
}
void OnTriggerEnter2D()
{
ground = true;
}
void OnTriggerExit2D()
{
ground = false;
}
private void Movement(float horizontal)
{
myRigidbody.velocity = new Vector2(horizontal * speed,myRigidbody.velocity.y);
}
private void Flip(float horizontal)
{
if (horizontal > 0 && !facingRight || horizontal < 0 && facingRight)
{
facingRight = !facingRight;
Vector3 theScale = transform.localScale;
theScale.x *= -1;
transform.localScale = theScale;
}
}
}
Weapon script
using System.Collections;
using System.Collections.Generic;
using UnityEngine;
public class weapon : MonoBehaviour
{
// Start is called before the first frame update
public bool right;
public Transform firepointR;
public GameObject bulletPrefab;
// Update is called once per frame
void Update()
{
if (Input.GetKeyDown("space"))
{
Debug.Log("Oh well");
Shoot();
}
}
void Shoot()
{
Instantiate(bulletPrefab, firepointR.position, firepointR.rotation);
}
}
bullet script
using System.Collections;
using System.Collections.Generic;
using UnityEngine;
public class bullet : MonoBehaviour
{
public bool left;
public float speed = 20;
public Rigidbody2D rb;
// Start is called before the first frame update
void Start()
{
rb.velocity = transform.right * speed;
}
// Update is called once per frame
void FixedUpdate()
{
Debug.Log(speed);
if (left == false)
{
transform.Rotate(0, 0, 180);
}
}
}
As i previously said i need my bullet (prefab) to go the opposite direction but whatever i do right now it will always go right.
Expanding on my comment:
Did you try reversing the velocity?
rb.velocity = -(transform.right * speed);
Note: There are instances when using a negative float wont return the opposite of the positive result. However, in this example, it will work just fine.
I imagine this will work also (and is probably the correct way of doing it):
rb.velocity = transform.left * speed;