Restrict rotation on X Z for rigidbodies

[Hesham]

Is there a way to restrict rotation for rigidbodies, to only the y-axis?

The reason is that I’m developing a 2d game, and most of the objects are simple planes with textures on them (Sprites). What I want is for them to collide and affect each others trajectory but without any rotation, in order for the plane to be always perfectly facing the camera.

Is this possible?

[anon_59178123]

AFAIK you can do that with a configurable joint, but I’m not sure if this is the best way to do that. For a full rotation lock you can use http://unity3d.com/support/documentation/ScriptReference/Rigidbody-freezeRotation.html Also you can give this a try http://unity3d.com/support/documentation/ScriptReference/Rigidbody-rotation.html I would definitely use this.

[Hesham]

Thanks, but freezing rotation in all axis is not what I intend to do, the sprite is ok to rotate around the y axis.

[Hesham]

Thinking about it, I think the LookAt script will work. I just need to place the target way behind the camera. Gonna try it out tonight and see.

[anon_76008222]

Here’s a great script that will limit an object to either X, Y or Z. You can choose which by changing the value in the Inspector:

public var forceBetweenXYZ:String=“x”;
private var Axis:Vector3;//desired depth
private var Rotation:Vector3;//desired rotation

function Awake(){
Axis=transform.position;//defines the starting X position as the desired X position
Rotation=transform.eulerAngles;//defines the starting rotation as the desired rotation
}
function Update(){//each frame
var spinforce:Vector3=gameObject.rigidbody.angularVelocity;//is the rotational force on this frame
var place:Vector3=gameObject.transform.position;//is the target position in world space on this frame

if(forceBetweenXYZ==“x”){
if(place.x!=Axis.x){//if the current X position IS NOT the desired X position then…
transform.position.x=Axis.x;//go to the desired X position
}
gameObject.rigidbody.angularVelocity.y=0;//stop rotating around y axis
gameObject.rigidbody.angularVelocity.z=0;//stop rotating around z axis
gameObject.transform.rotation.y=Rotation.y;//resets it to the desired y rotation
gameObject.transform.rotation.z=Rotation.z;//resets it to the desired y rotation
}else if(forceBetweenXYZ==“y”){
if(place.y!=Axis.y){//if the current X position IS NOT the desired X position then…
transform.position.y=Axis.y;//go to the desired X position
}
gameObject.rigidbody.angularVelocity.y=0;//stop rotating around y axis
gameObject.rigidbody.angularVelocity.x=0;//stop rotating around z axis
gameObject.transform.rotation.x=Rotation.x;//resets it to the desired y rotation
gameObject.transform.rotation.z=Rotation.z;//resets it to the desired y rotation
}else{
if(place.z!=Axis.z){//if the current X position IS NOT the desired X position then…
transform.position.z=Axis.z;//go to the desired X position
}
gameObject.rigidbody.angularVelocity.y=0;//stop rotating around y axis
gameObject.rigidbody.angularVelocity.x=0;//stop rotating around z axis
gameObject.transform.rotation.y=Rotation.y;//resets it to the desired y rotation
gameObject.transform.rotation.x=Rotation.x;//resets it to the desired y rotation
if(forceBetweenXYZ!=“z”){
print(“FORCING Z BY DEFAULT, USE X, Y, OR Z LOWERCASE”);
}
}
}

Not my script, I think I found it on Unity Answers. Props to the author.

[Wadoman]

I’m not a programmer, but I just did this with this code attached to the gameobject. My code restricts the Z axis and limits the rotation to only the z rotation.

function FixedUpdate () {
	transform.position.z = 0;
	transform.rotation.y = 0;
	transform.rotation.x = 0;
}

I don’t know if this is the most efficient way or proper coding to do it. I am looking into it more right now. If it’s only for a few objects then I think you can get away with it.

[Wadoman]

Ok to update my findings.

Testing on a 3G and Iphone 4. With about 14 objects with this code attached. The iPhone 4 ran fine, but the 3G got about 5 fps. taking out this code brought it back up to 30+FPS. I changed to using Configurable joints(Component → Physics -->Configurable Joint) on each object and it gave me the same affect with no FPS hit. So I would say if you only using it on a couple GameObjects then the previous code should be fine. If you have a lot of on screen GameObjects needing this then I would use the Configurable Joint.

Here is a thread discussing it.
http://forum.unity3d.com/threads/46901-Limiting-movement-rotation-on-the-z-axis?highlight=restrict+axis