Flipping a 2D Character that has physics objects attached to it

Hi guys

I'm prototyping a little game that has 2D characters with ragdoll physics as well as animations.

When I'd like to flip the character horizontally, animations work totally fine if I just scale the model by -1 in the Y axis. However physics breaks.

What's the correct / best way of flipping such character horizontally?

Just to give you an idea, I'm attaching a screenshot of the character. We're using: 2D Colliders, Rigid Bodies, and 2D Hinge joints.

Many thanks!

 

You can just use Transform.rotation instead of Transform.scale.
If you add 180 or subtract 180 degrees in the inspector on one of the axis it should flip your character.

Edit: If your character is a sprite you can also use the "flip" option of the Renderer.

 

Thanks Kaart. That was a good idea, but I've tried it and it also breaks physics. It looks like there's a conflict with the rigid bodies and joints when the character is rotated on the Y axis by 180 degrees. Collisions seem to work well at first sight.

Perhaps if we were using the 3D physics engine this wouldn't have been the case.

(Just correcting what I said above - the scale was on the X axis, so the rotation was on the Y axis)

Any other ideas would be appreciated.

 

You can't rotate using transform (or translate as a matter of fact) and Rigidbody2D, because the rigidbody2D have its own rotation: https://docs.unity3d.com/ScriptReference/Rigidbody2D-rotation.html

 

So, I can't scale, and can't rotate. I can't flip the sprite because it's a character composed of many sprites: leg, torso, etc, and we will have animation clips playing on these characters.

I thought about using the 3D physics engine (just to allow for rotation around the Y axis) but that would prevent us from using the stuff that's only in the 2D physics engine.

Any ideas would be appreciated...

 

Code (CSharp):

1. Quaternion rotation = Quaternion.LookRotation(myMove, Vector3.up);
2. transform.rotation = rotation;

appears to work well with rigibody2D
also :
https://weeklycoder.com/2015/07/20/unity-simple-2d-rotation-script/

 

Not sure I understand what you mean Samacvuk. What's "myMove" in your script?

Also, about your link, I'm not trying to rotate the 2D character, but literally "flip" it so the same animations and physics setup can be used when it's facing left or right...

 

myMove is just a generic name for a variable representing the direction you want to rotate and Vector3.up is the default value (you don't need to type it)

 

did you manage to solve this ?
Thanks

 

Took a whole day but i found a solution !
1) Storage all Rigidbody Rotations and the JointAngleLimits2D min/max OnAwake.
2) Calculate the angleoffset for all the connected Rigidboody (attachedRigidbody.rotation - connectedBody.rotation).
!!you need to use the valuse that you will receive OnAwake!!.
3) Flip the Objekt.
4)
JointAngleLimits2D temp = joint2D.limits;
temp.min = limit.min * -1 + angleoffset * 2;
temp.max = limit.max * -1 + angleoffset * 2;
joint2D.limits = temp;

on flip back just pass the defoult valuse-

works for me,hope it helps,

 

If you are using normal map for 2drenderer, scaling negatively on x axis also breaks rendering.

 

In Built-in RenderPipeline you can setup the shader to deal with the negativscaling,i guess."no idea on URP and HDRP". Negativscaling is the easiest way to flip but curses a lot of trouble.I simply find no easi and good way to flip my carackter, thet works for all scenarios.

 

Good Day If there're still people struggling to this,

I fixed mine by flipping the parent of all Physics objects you can see below, it might not be smooth but it does the job for me.

Code (CSharp):

1. public Transform Physics_Parent;
2. public Transform Holder;
3.  
4.  
5. public Transform Animation;
6. public Transform real;
7.  
8. public void flip()
9. {
10.        
11.  
12.      
13.         Holder.transform.parent = real;
14.         Physics_Parent.transform.parent = Holder;
15.  
16.         Vector3 theScale1 = Animation.localScale;
17.         theScale1.x *= -1;
18.         Animation.localScale = theScale1;
19.  
20.         Vector3 theScale = Holder.localScale;
21.         theScale.x *= -1;
22.         Holder.localScale = theScale;
23.  
24.         Physics_Parent.transform.parent = real;
25.         Holder.transform.parent = null;
26.  
27.        
28.  
29.  
30.  
31.  
32. }