Control player while moving it in a direction

I want to be able to control the player left right and jump while constantly moving it in a direction at a constant speed. Is there any way to do this? I've tried moving the player forward using AddForce(), but it moves faster over time.

 

I forgot to mention that I'm making a 3D project, sorry.

 

If you just want to move left and right while going at constant speed, and you're not interested in physics. You can set the Rigidbody speed directly to a speed you want. leaving the Y axis free so as not to prevent the jump.

Code (CSharp):

1. Vector3 vel = rigidbody.velocity;
2. vel.x = movement.x * speed;
3. vel.z = movement.z * speed;
4. rigidbody.velocity = vel;

 

(sorry for replying late)

I've tried your code and it didn't work, it generated an error: The name 'movement' does not exist in the current context

 

sorry I used it for me in a project. movement is a vector used to describe the direction to make the object walk.
I called my movement vector and updated it in Update like this:

Code (CSharp):

1. float Horizontal = Input.GetAxis("Horizontal");
2. float Vertical = Input.GetAxis("Vertical");
3. movement = (transform.right * Horizontal + transform.forward * Vertical);

if you want to move based on how the camera is facing then use this:

Code (CSharp):

1. movement = (Camera.main.transform.right * Horizontal + Camera.main.transform.forward * Vertical);

PS: speed is a float, you decide to indicate the speed at which the rigidbody moves