Unity-Technologies/UnityCsReference · error · Exception

no duplication of scenes is allowed

Error message

no duplication of scenes is allowed

What it means

Lightmapping.BakeMultipleScenes explicitly rejects duplicate scene paths in the input string[] with System.Exception, because Unity loads each path additively for the combined bake and duplicates would conflict. The comparison is an exact string equality check (ordinal, case-sensitive).

Source

Thrown at Editor/Mono/GI/Lightmapping.bindings.cs:608

        public static extern LightingSettings GetLightingSettingsForScene(Scene scene);

        [FreeFunction]
        public static extern LightingDataAsset GetLightingDataAssetForScene(Scene scene);

        [FreeFunction(ThrowsException = true)]
        public static extern void SetLightingDataAssetForScene(Scene scene, LightingDataAsset lda);

        public static void BakeMultipleScenes(string[] paths)
        {
            if (paths.Length == 0)
                return;

            for (int i = 0; i < paths.Length; i++)
            {
                for (int j = i + 1; j < paths.Length; j++)
                {
                    if (paths[i] == paths[j])
                        throw new System.Exception("no duplication of scenes is allowed");
                }
            }

            if (!EditorSceneManager.SaveCurrentModifiedScenesIfUserWantsTo())
                return;

            var sceneSetup = EditorSceneManager.GetSceneManagerSetup();

            // Restore old scene setup once the bake finishes
            Action OnBakeFinish = null;
            OnBakeFinish = () =>
            {
                EditorSceneManager.SaveOpenScenes();
                if (sceneSetup.Length > 0)
                    EditorSceneManager.RestoreSceneManagerSetup(sceneSetup);
                Lightmapping.bakeCompleted -= OnBakeFinish;
            };

View on GitHub (pinned to 225b0fbdb5)

Solutions

1. Deduplicate paths before calling: paths = paths.Distinct(System.StringComparer.Ordinal).ToArray();
2. Build the array from a HashSet<string> using an ordinal comparer.
3. Reject empty/null entries and verify each path resolves to a distinct scene.

Example fix

// before
Lightmapping.BakeMultipleScenes(paths);
// after
var deduped = paths.Where(p => !string.IsNullOrEmpty(p))
                   .Distinct(System.StringComparer.Ordinal)
                   .ToArray();
Lightmapping.BakeMultipleScenes(deduped);

var deduped = paths.Where(p => !string.IsNullOrEmpty(p))
                   .Distinct(System.StringComparer.Ordinal)
                   .ToArray();
Lightmapping.BakeMultipleScenes(deduped);

When it happens

Trigger: Passing a string[] containing the same path twice (e.g. {"Assets/A.unity", "Assets/A.unity"}); building the array from selection/dependencies without dedup; including the active scene path that is also listed.

Common situations: Programmatic multi-scene bake scripts that assemble paths from a set that lost uniqueness; path strings that differ only by casing are treated as distinct (and both load), while exact duplicates throw.

Related errors

• index must be between 0 and {albedoTexturePropertiesCount -
• index must be between 0 and {emissiveTexturePropertiesCount
• index must be between 0 and {transmissiveTextureCount - 1},
• index must be between 0 and {transmissiveTexturePropertiesCo
• index must be between 0 and {GetCookieCount() - 1}, but was

AI-assisted analysis of Unity-Technologies/UnityCsReference@225b0fbdb5 (2026-08-13). Data as JSON: /api/errors/ef238c74f0375e1d. Report an issue: GitHub.