Helper to deep-copy a TerrainData object in Unity3D - Updated for Unity 2021.2

TerrainDataCloner.cs

using UnityEngine;

/// <summary>
/// Provides means to deep-copy a TerrainData object because Unitys' built-in "Instantiate" method
/// will miss some things and the resulting copy still shares data with the original.
/// </summary>
public class TerrainDataCloner {
    /// <summary>
    /// Creates a real deep-copy of a TerrainData
    /// </summary>
    /// <param name="original">TerrainData to duplicate</param>
    /// <returns>New terrain data instance</returns>
    public static TerrainData Clone(TerrainData original) {
        TerrainData dup = new TerrainData();

        dup.alphamapResolution = original.alphamapResolution;
        dup.baseMapResolution = original.baseMapResolution;
        dup.detailPrototypes = CloneDetailPrototypes(original.detailPrototypes);
        dup.enableHolesTextureCompression = original.enableHolesTextureCompression;
        dup.heightmapResolution = original.heightmapResolution;
        dup.size = original.size;
        dup.terrainLayers = original.terrainLayers;
        dup.wavingGrassAmount = original.wavingGrassAmount;
        dup.wavingGrassSpeed = original.wavingGrassSpeed;
        dup.wavingGrassStrength = original.wavingGrassStrength;
        dup.wavingGrassTint = original.wavingGrassTint;

        dup.SetAlphamaps(0, 0, original.GetAlphamaps(0, 0, original.alphamapWidth, original.alphamapHeight));
        dup.SetDetailResolution(original.detailResolution, original.detailResolutionPerPatch);
        for (int n = 0; n < original.detailPrototypes.Length; n++) {
            dup.SetDetailLayer(0, 0, n, original.GetDetailLayer(0, 0, original.detailWidth, original.detailHeight, n));
        }
        dup.SetHeights(0, 0, original.GetHeights(0, 0, original.heightmapResolution, original.heightmapResolution));
        dup.SetHoles(0, 0, original.GetHoles(0, 0, original.holesResolution, original.holesResolution));

        dup.treePrototypes = CloneTreePrototypes(original.treePrototypes);
        dup.treeInstances = CloneTreeInstances(original.treeInstances);
        return dup;
    }

    /// <summary>
    /// Deep-copies an array of detail prototype instances
    /// </summary>
    /// <param name="original">Prototypes to clone</param>
    /// <returns>Cloned array</returns>
    static DetailPrototype[] CloneDetailPrototypes(DetailPrototype[] original) {
        DetailPrototype[] protoDuplicate = new DetailPrototype[original.Length];

        for (int n = 0; n < original.Length; n++) {
            protoDuplicate[n] = new DetailPrototype {
                dryColor = original[n].dryColor,
                healthyColor = original[n].healthyColor,
                holeEdgePadding = original[n].holeEdgePadding,
                maxHeight = original[n].maxHeight,
                maxWidth = original[n].maxWidth,
                minHeight = original[n].minHeight,
                minWidth = original[n].minWidth,
                noiseSeed = original[n].noiseSeed,
                noiseSpread = original[n].noiseSpread,
                prototype = original[n].prototype,
                prototypeTexture = original[n].prototypeTexture,
                renderMode = original[n].renderMode,
                useInstancing = original[n].useInstancing,
                usePrototypeMesh = original[n].usePrototypeMesh
            };
        }
        return protoDuplicate;
    }

    /// <summary>
    /// Deep-copies an array of tree prototype instances
    /// </summary>
    /// <param name="original">Prototypes to clone</param>
    /// <returns>Cloned array</returns>
    static TreePrototype[] CloneTreePrototypes(TreePrototype[] original) {
        TreePrototype[] protoDuplicate = new TreePrototype[original.Length];

        for (int n = 0; n < original.Length; n++) {
            protoDuplicate[n] = new TreePrototype {
                bendFactor = original[n].bendFactor,
                prefab = original[n].prefab,
            };
        }
        return protoDuplicate;
    }

    /// <summary>
    /// Deep-copies an array of tree instances
    /// </summary>
    /// <param name="original">Trees to clone</param>
    /// <returns>Cloned array</returns>
    static TreeInstance[] CloneTreeInstances(TreeInstance[] original) {
        TreeInstance[] treeInst = new TreeInstance[original.Length];

        System.Array.Copy(original, treeInst, original.Length);
        return treeInst;
    }
}