Functions for getting and applying inverse transforms

TransformInverter.cs

using UnityEngine;

/// <summary>
/// Provides utility methods for inverting transforms in Unity.
/// </summary>
public static class TransformInverter
{
    /// <summary>
    /// Inverts the local transform of the target based on the source transform.
    /// Equivalent to the LocalInvert method in the original MonoBehaviour.
    /// </summary>
    /// <param name="target">The Transform to apply the inversion to.</param>
    /// <param name="source">The Transform to take the inverse from.</param>
    public static void InvertLocal(Transform target, Transform source)
    {
        if (source == null || target == null)
        {
            Debug.LogWarning("InvertLocal: Source or target transform is null.");
            return;
        }

        // Get the source's local transform components
        Vector3 sourceLocalPosition = source.localPosition;
        Quaternion sourceLocalRotation = source.localRotation;
        Vector3 sourceLocalScale = source.localScale;

        // Invert the scale
        Vector3 inverseScale = new Vector3(
            sourceLocalScale.x != 0 ? 1f / sourceLocalScale.x : 0,
            sourceLocalScale.y != 0 ? 1f / sourceLocalScale.y : 0,
            sourceLocalScale.z != 0 ? 1f / sourceLocalScale.z : 0
        );
        target.localScale = inverseScale;

        // Invert the rotation
        Quaternion inverseRotation = Quaternion.Inverse(sourceLocalRotation);
        target.localRotation = inverseRotation;

        // Invert the position
        Vector3 scaledPosition = Vector3.Scale(inverseScale, sourceLocalPosition);
        Vector3 rotatedPosition = inverseRotation * scaledPosition;
        Vector3 inversePosition = -rotatedPosition;
        target.localPosition = inversePosition;
    }

    /// <summary>
    /// Inverts the global (world) transform of the target based on the source transform.
    /// Equivalent to the GlobalInvert method in the original MonoBehaviour.
    /// </summary>
    /// <param name="target">The Transform to apply the inversion to.</param>
    /// <param name="source">The Transform to take the inverse from.</param>
    public static void InvertGlobal(Transform target, Transform source)
    {
        if (source == null || target == null)
        {
            Debug.LogWarning("InvertGlobal: Source or target transform is null.");
            return;
        }

        // Get the source's world transform components
        Vector3 sourceWorldPosition = source.position;
        Quaternion sourceWorldRotation = source.rotation;
        Vector3 sourceWorldScale = source.lossyScale;

        // Invert the scale
        Vector3 inverseScale = new Vector3(
            sourceWorldScale.x != 0 ? 1f / sourceWorldScale.x : 0,
            sourceWorldScale.y != 0 ? 1f / sourceWorldScale.y : 0,
            sourceWorldScale.z != 0 ? 1f / sourceWorldScale.z : 0
        );
        target.localScale = inverseScale;

        // Invert the rotation
        Quaternion inverseRotation = Quaternion.Inverse(sourceWorldRotation);
        target.rotation = inverseRotation;

        // Invert the position
        Vector3 scaledPosition = Vector3.Scale(inverseScale, sourceWorldPosition);
        Vector3 rotatedPosition = inverseRotation * scaledPosition;
        Vector3 inversePosition = -rotatedPosition;
        target.position = inversePosition;
    }

    /// <summary>
    /// Retrieves the inverse local transform components based on the source transform.
    /// </summary>
    /// <param name="source">The Transform to take the inverse from.</param>
    /// <param name="inversePosition">Output inverse local position.</param>
    /// <param name="inverseRotation">Output inverse local rotation.</param>
    /// <param name="inverseScale">Output inverse local scale.</param>
    public static void GetInverseLocal(Transform source, out Vector3 inversePosition, out Quaternion inverseRotation, out Vector3 inverseScale)
    {
        if (source == null)
        {
            Debug.LogWarning("GetInverseLocal: Source transform is null.");
            inversePosition = Vector3.zero;
            inverseRotation = Quaternion.identity;
            inverseScale = Vector3.one;
            return;
        }

        // Get the source's local transform components
        Vector3 sourceLocalPosition = source.localPosition;
        Quaternion sourceLocalRotation = source.localRotation;
        Vector3 sourceLocalScale = source.localScale;

        // Invert the scale
        inverseScale = new Vector3(
            sourceLocalScale.x != 0 ? 1f / sourceLocalScale.x : 0,
            sourceLocalScale.y != 0 ? 1f / sourceLocalScale.y : 0,
            sourceLocalScale.z != 0 ? 1f / sourceLocalScale.z : 0
        );

        // Invert the rotation
        inverseRotation = Quaternion.Inverse(sourceLocalRotation);

        // Invert the position
        Vector3 scaledPosition = Vector3.Scale(inverseScale, sourceLocalPosition);
        Vector3 rotatedPosition = inverseRotation * scaledPosition;
        inversePosition = -rotatedPosition;
    }

    /// <summary>
    /// Retrieves the inverse global (world) transform components based on the source transform.
    /// </summary>
    /// <param name="source">The Transform to take the inverse from.</param>
    /// <param name="inversePosition">Output inverse world position.</param>
    /// <param name="inverseRotation">Output inverse world rotation.</param>
    /// <param name="inverseScale">Output inverse world scale.</param>
    public static void GetInverseGlobal(Transform source, out Vector3 inversePosition, out Quaternion inverseRotation, out Vector3 inverseScale)
    {
        if (source == null)
        {
            Debug.LogWarning("GetInverseGlobal: Source transform is null.");
            inversePosition = Vector3.zero;
            inverseRotation = Quaternion.identity;
            inverseScale = Vector3.one;
            return;
        }

        // Get the source's world transform components
        Vector3 sourceWorldPosition = source.position;
        Quaternion sourceWorldRotation = source.rotation;
        Vector3 sourceWorldScale = source.lossyScale;

        // Invert the scale
        inverseScale = new Vector3(
            sourceWorldScale.x != 0 ? 1f / sourceWorldScale.x : 0,
            sourceWorldScale.y != 0 ? 1f / sourceWorldScale.y : 0,
            sourceWorldScale.z != 0 ? 1f / sourceWorldScale.z : 0
        );

        // Invert the rotation
        inverseRotation = Quaternion.Inverse(sourceWorldRotation);

        // Invert the position
        Vector3 scaledPosition = Vector3.Scale(inverseScale, sourceWorldPosition);
        Vector3 rotatedPosition = inverseRotation * scaledPosition;
        inversePosition = -rotatedPosition;
    }

    /// <summary>
    /// Retrieves the inverse local transform as a TransformData structure based on the source transform.
    /// </summary>
    /// <param name="source">The Transform to take the inverse from.</param>
    /// <returns>A TransformData struct containing the inverse position, rotation, and scale.</returns>
    public static TransformData GetInverseLocal(Transform source)
    {
        GetInverseLocal(source, out Vector3 inversePosition, out Quaternion inverseRotation, out Vector3 inverseScale);
        return new TransformData(inversePosition, inverseRotation, inverseScale);
    }

    /// <summary>
    /// Retrieves the inverse global (world) transform as a TransformData structure based on the source transform.
    /// </summary>
    /// <param name="source">The Transform to take the inverse from.</param>
    /// <returns>A TransformData struct containing the inverse position, rotation, and scale.</returns>
    public static TransformData GetInverseGlobal(Transform source)
    {
        GetInverseGlobal(source, out Vector3 inversePosition, out Quaternion inverseRotation, out Vector3 inverseScale);
        return new TransformData(inversePosition, inverseRotation, inverseScale);
    }

    /// <summary>
    /// Represents a set of transformation data: position, rotation, and scale.
    /// </summary>
    public struct TransformData
    {
        public Vector3 Position;
        public Quaternion Rotation;
        public Vector3 Scale;

        /// <summary>
        /// Initializes a new instance of the TransformData struct.
        /// </summary>
        /// <param name="position">The position component.</param>
        /// <param name="rotation">The rotation component.</param>
        /// <param name="scale">The scale component.</param>
        public TransformData(Vector3 position, Quaternion rotation, Vector3 scale)
        {
            Position = position;
            Rotation = rotation;
            Scale = scale;
        }
    }
}