Rigidbody.Addforce makes object skip

Question

I'm working on a first person controller and i'm using Rigidbody to make the movement for the controller.

Altough i notice that when i move my character around on a simple plane, it starts skipping(jumping). I don't want to freeze the Y position, because i want my character to be jumping, and go up and down hills ect. Anyone have any tips on making this skipping disappear?

 Direction = new Vector3(0,0,0);
         if (Input.GetKey(KeyCode.W))
         {
             Direction += Vector3.forward;
         }
         if (Input.GetKey(KeyCode.A))
         {
             Direction += Vector3.left;
         }
         if (Input.GetKey(KeyCode.D))
         {
             Direction += Vector3.right;
         }
         if (Input.GetKey(KeyCode.S))
         {
             Direction += Vector3.back;    
         }
         if (Input.GetKey(KeyCode.Space) && CurrentlyJumping == false)
         {
             CurrentlyJumping = true;
         }
             CharSpeed = InputSpeed;
             Direction.Normalize();
             rigidbody.AddRelativeForce (Direction * CharSpeed);

This is the function i'm calling for movement.

Gravity is on by the way

Answer 1

To fix the skipping, what people usually do is lower the gravity when the character 'is grounded' (has ground under his feet). For this to work, first the gravity on the rigidbody has to be disabled. Second, gravity has to be applied manually.

If you want to make the controller less slidy, play with the drag/speed settings to get the desired result.

My usual rigidbody settings.

Also, make sure to always execute additive Physics functions in the FixedUpdate() function:

 var Direction : Vector3 = Vector3.zero;
 var Speed : float = 5;
 var JumpStrength : float = 5;
 var HalfCharacterHeight : float = 1;
 var DefaultGravity : float = 9.81;
 var GroundedGravity : float = 0.1;
 private var gravity : float = 9.81;
 private var isGrounded : boolean = false;
 
 function Update () {

      //we cast a ray downwards to the characters feet, to check if he's grounded
      isGrounded = Physics.Raycast(transform.position, -transform.up, HalfCharacterHeight);

      //change the gravity setting to Default/Grounded gravity based on the result of the raycast
      if(isGrounded) gravity = GroundedGravity;
      else gravity = DefaultGravity;
 
      Direction = Vector3.zero;
      
      //I'm using unity's input manager instead. You can change this in Edit/P.Settings/Input
      Direction.x = Input.GetAxis("Horizontal"); //you can also change this to 
      Direction.z = Input.GetAxis( "Vertical" ); //GetAxisRaw

      if(Direction.magnitude > 0) //if the direction isn't zero normalize it
           Direction = Direction.normalized; //so that diagonal movement isn't faster

      //if the space key was pressed and the character is grounded, jump!
      if(Input.GetKeyDown(KeyCode.Space) && isGrounded) {
           //using Impulse, to make the jump more realistic               
           rigidbody.AddForce( transform.up*JumpStrength,ForceMode.Impulse);
      }
 }
 
 function FixedUpdate () {
      
      if(Direction.magnitude > 0) //if the direction isn't zero add force
           rigidbody.AddRelativeForce(Direction*Speed); 

      rigidbody.AddRelativeForce(-transform.up*gravity); //apply gravity
 }

You could also try changing the Physics(Fixed) timestep in the Edit/Project Settings/Time menu. This can also solve fast rigidbodies flying trough walls.

Time settings

---David

Answer 2

Answer by DezBoyle · Jun 18, 2018 at 06:22 PM

Turn on interpolation on your player's rigidbody.

alt text

capture.png (27.3 kB)

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Richmar1 · Apr 27, 2020 at 04:23 PM 0

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That Solved It. Thanks!

Answer 3

Answer by electricsauce · Mar 04, 2013 at 03:00 PM

You might want to try changing your inputs to:

float h = input.getAxis("Horizontal"); float v = input.getAxis("Vertical"); direction = (h, v, 0);

When you add force with a getbuttondown the full amount of the force is added immediately, but the axis is a little smoother.

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SimonDiamond · Mar 04, 2013 at 09:22 PM 0

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I'll try it out, thanks!

SimonDiamond · Mar 05, 2013 at 08:56 AM 0

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unfortionatly this didn't do much difference, and the GetKeyDown only seems to disable my forward and back. With it i can only go left or right. The cause of the problem is probably behind the skipping aswell.

SimonDiamond · Mar 05, 2013 at 09:01 AM 0

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But the input.getaxis part made my Controller so much better so thanks!

Answer 4

Answer by LunaArgenteus · Mar 04, 2013 at 11:11 PM

Check to see if you have more than one collider active on the object - if you've mistakenly done this, the object will push itself / jerk in unintended directions.

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SimonDiamond · Mar 05, 2013 at 08:40 AM 0

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I only to have one box collider active, without On Trigger. And the floor i'm walking on making my object skip has a simple Mesh Collider. But that shouldn't be a problem...

Answer 5

Answer by SimonDiamond · Mar 05, 2013 at 10:47 AM

Well i guess it's a little embarrassing but i solved the skipping problem by just changing the way i move. I stopped using Rigidbody and simply used transform.translate. With a little help of the nice people answering this question i solved it!

This is the code.

 float h = Input.GetAxis("Horizontal");
         Vector3 Direction = new Vector3(h, 0, 0);
         float CharSpeed = InputSpeed;
         
         if (Input.GetKey(KeyCode.W))
         {
             Direction += Vector3.forward;
         }
         if (Input.GetKey(KeyCode.S))
         {
             Direction += Vector3.back;    
         }
         if (Input.GetKey(KeyCode.A))
         {
             Direction += Vector3.left;    
         }
         if (Input.GetKey(KeyCode.D))
         {
             Direction += Vector3.right;    
         }
         Direction.Normalize();
         transform.Translate(Direction * CharSpeed);

I'm still using Rigidbody for gravity and ect, but the reason why i used AddForce from the start was because i was having problems with the movement adjusting to the camera angle. Hope this will help anyone else who's having similiar problems.

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LunaArgenteus · Mar 05, 2013 at 11:20 AM 0

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The only problem with that is that by using transform.Translate, you are "teleporting" your object and not checking to see if you are hitting anything along the way. Perhaps you might want to consider using a CharacterController.

http://docs.unity3d.com/Documentation/ScriptReference/CharacterController.html

SimonDiamond · Mar 05, 2013 at 12:11 PM 0

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I'm actually trying to create "sort of" my own charactercontroller. That's why i'm not using Unitys CharacterController. But thanks for the advice!

DavidDebnar · Mar 05, 2013 at 12:52 PM 0

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You do realise that by using Translate, you'll also have to write your own physics interaction system. Also, by doing this, you just turned of Y movement, which you said you didn't want to be "freezed", because you want your character to be jumping and going down hills, which won't be happening without a physics engine.

DavidDebnar · Mar 05, 2013 at 12:56 PM 0

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You can also reduce your code to:

 transform.Translate(Vector3(Input.GetAxis("Horizontal"),0,Input.GetAxis("Vertical")).normalized*InputSpeed);

That's 22 lines reduced to 1.

SimonDiamond · Mar 05, 2013 at 01:50 PM 0

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I didn't know that actually...i guess i'm going back to AddForce. Thanks for the advice Dávid. I really appreciate it! You're a sun among stars. Or something.

Rigidbody.Addforce makes object skip

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