Create individual prefabs

Hi there,

I want to create a pointcloud. For this I have a Chunk class which can create voxel at any position.
Because of the size of my cloud I have to seperate it into several chunks. Each chunk contains 8125 voxel.
For this I created a world class where I instantiate a chunk and then I want to send it the coordiantes for the voxels.
In someway it works and I can see two voxels but then I get
NullReferenceException: Object reference not set to an instance of an object” and I don’t unterstand why. Here is my code:

From world script:

public GameObject chunkPrefab;
public GameObject newChunkObject;
public void CreateChunk(Vector3[] coordinates)
    {
        newChunkObject = Instantiate(chunkPrefab, new Vector3(0,0,0), 
                             Quaternion.Euler(Vector3.zero)) as GameObject;

        Chunk newChunk = newChunkObject.GetComponent<Chunk>();

       newChunk.createBlockAt(0,0, 0);
    }

From chunk script:

public virtual void createBlockAt(int x, int y, int z)
    {
        RenderMesh(Blockdata(x, y, z));  
    }

private MeshData Blockdata(int x, int y, int z)
    {
        meshData.vertices.Add(new Vector3(x - 0.5f, y + 0.5f, z + 0.5f));
        meshData.vertices.Add(new Vector3(x + 0.5f, y + 0.5f, z + 0.5f));
        meshData.vertices.Add(new Vector3(x + 0.5f, y + 0.5f, z - 0.5f));
        meshData.vertices.Add(new Vector3(x - 0.5f, y + 0.5f, z - 0.5f));

        meshData.vertices.Add(new Vector3(x - 0.5f, y - 0.5f, z - 0.5f));
        meshData.vertices.Add(new Vector3(x + 0.5f, y - 0.5f, z - 0.5f));
        meshData.vertices.Add(new Vector3(x + 0.5f, y - 0.5f, z + 0.5f));
        meshData.vertices.Add(new Vector3(x - 0.5f, y - 0.5f, z + 0.5f));

        meshData.AddQuadTriangles();
        
        return meshData;
    }

private void RenderMesh(MeshData meshData)
    {
        filter.mesh.Clear();
        filter.mesh.vertices = meshData.vertices.ToArray();
        filter.mesh.triangles = meshData.triangles.ToArray();
        filter.mesh.RecalculateNormals()
   }

the error always ends in RenderMesh method.

I Also tried to send my chunk along with the methods but nothing changed. Hope someone can help me.
Thank you.

EDIT:
My prefab contains a script which creates individual meshes. I can change the mesh by individual coordinates.

Got it:

 private void RenderMesh(MeshData meshData)
    {
        MeshFilter filter = GetComponent<MeshFilter>();
        filter.mesh.Clear();
        filter.mesh.vertices = meshData.vertices.ToArray();
        filter.mesh.triangles = meshData.triangles.ToArray();
        filter.mesh.RecalculateNormals();
    }

Need to create the mesh in my function. In someway it is empty when I call it from world.