Unity-Technologies/UnityCsReference · error · ArgumentNullException

Mesh array is null

Error message

Mesh array is null

What it means

Thrown by the Mesh[] overload of AcquireReadOnlyMeshData when the meshes array is null. The method acquires read-only CPU access to the mesh vertex/index data of multiple meshes and requires a non-null array.

Source

Thrown at Editor/Mono/MeshUtility.bindings.cs:59

            if (uvCount != 3 * triCount)
            {
                Debug.LogError("mesh contains " + triCount + " triangles but " + uvCount + " uvs are provided");
                return false;
            }
            return SetPerTriangleUV2NoCheck(src, triUV);
        }

        extern internal static Vector2[] ComputeTextureBoundingHull(Texture texture, int vertexCount);

        public static Mesh.MeshDataArray AcquireReadOnlyMeshData(Mesh mesh)
        {
            return new Mesh.MeshDataArray(mesh, false);
        }

        public static Mesh.MeshDataArray AcquireReadOnlyMeshData(Mesh[] meshes)
        {
            if (meshes == null)
                throw new ArgumentNullException(nameof(meshes), "Mesh array is null");
            return new Mesh.MeshDataArray(meshes, meshes.Length, false);
        }

        public static Mesh.MeshDataArray AcquireReadOnlyMeshData(List<Mesh> meshes)
        {
            if (meshes == null)
                throw new ArgumentNullException(nameof(meshes), "Mesh list is null");
            return new Mesh.MeshDataArray(NoAllocHelpers.ExtractArrayFromList(meshes), meshes.Count, false);
        }
    }
}

View on GitHub (pinned to 225b0fbdb5)

Solutions

1. Allocate and populate the array before calling; if no meshes exist, handle that case explicitly rather than passing null.
2. Null-check the array and log which source produced null.
3. Use the List<Mesh> overload if you already have a list, to avoid manual array management.

Example fix

// before
var data = MeshUtility.AcquireReadOnlyMeshData(meshes);

// after
if (meshes == null || meshes.Length == 0) return;
var data = MeshUtility.AcquireReadOnlyMeshData(meshes);

if (meshes == null || meshes.Length == 0) return;

static bool HasMeshes(Mesh[] m) => m != null && m.Length > 0;

try { var data = MeshUtility.AcquireReadOnlyMeshData(meshes); }
catch (ArgumentNullException ex) when (ex.ParamName == "meshes") { Debug.LogWarning("No meshes to acquire."); }

When it happens

Trigger: Calling AcquireReadOnlyMeshData((Mesh[])null), or passing an array reference that was never allocated. Distinct from the single-Mesh overload and the List<Mesh> overload, which have their own null checks.

Common situations: Editor tooling that collects meshes from a hierarchy and passes the result without checking for null (e.g. when no meshes were found). A field defaulting to null passed directly.

Related errors

• Mesh list is null
• src
• triUV
• Unknown vertex format {format}
• Scene path cannot be null or empty.

AI-assisted analysis of Unity-Technologies/UnityCsReference@225b0fbdb5 (2026-08-13). Data as JSON: /api/errors/a99ddfe5bf6df271. Report an issue: GitHub.