today's chatgpt experiment was a simple one, but one that still left me exhausted because, once again, I had to hold its hand until it came upon an answer
me: In Unity, I have a parent gameobject with a child gameobject inside it. The child gameobject is a plane. I want to be able to rotate the parent gameobject without the plane rotating. How can I accomplish this without changing the hierarchy?
chatgpt: There are a couple of ways to tackle this problem:
- Creating a script for the child gameobject to always maintain a fixed rotation:
In this way, you can rotate the parent object as you want, but the child object will always return to its original rotation. You can do this by using the Update() function, which will keep the child's rotation constant.
Here's an example:
using UnityEngine;
public class MaintainRotation : MonoBehaviour
{
Quaternion initialRotation;
void Start()
{
initialRotation = transform.rotation;
}
void Update()
{
transform.rotation = initialRotation;
}
}
Just attach this script to the child gameobject (the plane). This script will save its rotation at the start of the game and will constantly apply it every frame in the game.
- (FAUNA'S NOTE: yes, 1 again) Using Unity's InverseTransformDirection function:
Another approach is to apply inverse transformations. This way, when you rotate the parent object, the child object will do an inverse rotation to stay in the same orientation. This also needs a script on the child object:
using UnityEngine;
public class InverseRotation : MonoBehaviour
{
public Transform parentTransform;
void Update()
{
Vector3 parentEulerAngles = parentTransform.rotation.eulerAngles;
transform.rotation = Quaternion.Euler(-parentEulerAngles);
}
}
In this script, replace parentTransform with the parent object's transform in the Inspector. The child object will now rotate in the opposite direction to the parent, keeping it looking the same direction as before.
Remember, both methods will keep the child's rotation constant relative to the world, not to the parent object. If you want to keep the rotation constant relative to the parent (for example, if the plane should always face the parent object), you would need a different approach.
me: this doesn't work. The plane rotates 6.28319 radians for every degree the cube rotates
chatgpt: I apologize for the confusion. The issue you are experiencing might be because Euler angles and Quaternion rotations don't exactly behave in the same manner.
You may want to directly compensate for the parent's rotation by applying the inverse of the parent's rotation to the child. You can do this using Quaternion.Inverse() function in Unity.
Here is an example of how you can achieve this:
using UnityEngine;
public class InverseRotation : MonoBehaviour
{
public Transform parentTransform;
void LateUpdate()
{
transform.rotation = Quaternion.Inverse(parentTransform.rotation);
}
}
In this script, parentTransform should be set to the parent object's transform in the Inspector. This script will apply an inverse rotation to the child for every rotation applied to the parent, effectively keeping its orientation the same relative to the world.
Please note that this script uses LateUpdate() instead of Update(). This is to ensure that the parent's rotation has been fully applied for this frame before we compute the inverse. If we were to use Update(), we might get one frame behind, which could result in noticeable jitter or lag in the child's movement.
me: Now the plane just rotates in the opposite direction. I want it to always maintain its initial rotation
chatgpt: I apologize for the confusion. The idea here is to store the initial rotation and apply that rotation every frame to the child gameobject. If you don't want the child to rotate with the parent, then a simple script like the following should be what you need:
using UnityEngine;
public class MaintainRotation : MonoBehaviour
{
private Quaternion initialRotation;
private void Start()
{
initialRotation = transform.rotation;
}
private void Update()
{
transform.rotation = initialRotation;
}
}
Attach this script to the child object. It will save the initial rotation and apply it on every frame, effectively ignoring any rotation that might be inherited from the parent object. Make sure that the object's rotation is set correctly before the game starts, as this will be the rotation that the script maintains.
If the initial rotation should be set programmatically, you can set initialRotation to whatever value you need in the Start() function.
me: This doesn't work because the parent will change the rotation of the child. Convert from a global rotation of 0,0,0 to an appropriate localrotation
chatgpt: I see, you're correct. If the parent object rotates, it will affect the local rotation of its child objects, which might not be the desired effect. To maintain the child's rotation in world space constant while the parent object is rotating, you could use the rotation and localRotation properties of the Transform component.
The rotation property represents the rotation of the object in world space, whereas localRotation represents the rotation relative to the object's parent. So, you could set the localRotation property based on the desired rotation and the rotation of the parent object. The result should be that the child maintains its orientation in world space.
Here is how to do it:
using UnityEngine;
public class MaintainWorldRotation : MonoBehaviour
{
public Quaternion desiredWorldRotation;
void Start()
{
desiredWorldRotation = transform.rotation; // Set to current rotation in world space
}
void Update()
{
// Compute the required local rotation by taking into account the parent's rotation
transform.localRotation = Quaternion.Inverse(transform.parent.rotation) * desiredWorldRotation;
}
}
This script should be attached to the child object (the plane). It records the initial rotation in world space and then in each frame sets the local rotation so that the object maintains its initial orientation in world space, regardless of the rotation of the parent object.
This is where chatgpt finally got it right, even though I had to guide it the whole way there. This really shoulda been a gimme but instead it struggled with it because its conceptualization skills are a mess since it's just spicy autocorrect
