Problem with making mesh at runtime. (Unity3d)

Question

I'm trying to make mesh with Vector3 data from database at runtime.

Here is my code

private IEnumerator CreateShape()
{
    int count = 0;

    triangles = new int[x_size * y_size * 6];

    //index buffer
    for (int i = 0; i < x_size - 1; i++)
    {
        for (int j = 0; j < y_size - 1; j++)
        {
            triangles[((i * y_size + j) * 6) + 0] = i * y_size + j;
            triangles[((i * y_size + j) * 6) + 1] = (i + 1) * y_size + j;
            triangles[((i * y_size + j) * 6) + 2] = i * y_size + j + 1;
            triangles[((i * y_size + j) * 6) + 3] = i * y_size + j + 1;
            triangles[((i * y_size + j) * 6) + 4] = (i + 1) * y_size + j;
            triangles[((i * y_size + j) * 6) + 5] = (i + 1) * y_size + j + 1;
        }
        yield return new WaitForSeconds(0.01f);
    }
}

And check updates for updating Mesh data..

private void UpdateMesh()
{
    mesh.Clear();

    mesh.vertices = vertices;
    mesh.triangles = triangles;
    mesh.RecalculateNormals();
}

Vertices data has no problem, cuz i checked it with different way.

private void OnDrawGizmos()
{
    if (vertices[x_size * y_size - 1] != Vector3.zero)
    {
        for (int i = 0; i < x_size - 1; i++)
        {
            for (int j = 0; j < y_size - 1; j++)
            {
                Gizmos.DrawSphere(vertices[i * y_size + j], .1f);
            }
        }
    }
}

Checked whether vertices data is wrong or not with gizmos but the data has no probs:

It should form a simple plane mesh shape, but it goes back to the start point and continue making in the middle of mesh-create-process..

What i expected:

But it goes wrong:

It seemed somehow internal index buffer calculation goes wrong..

Vertices data is about 160,000ea Vector3, and tris is also about 160,000*6 = 1,000,000ea integer.

Maybe the data is too much for making mesh while runtime at all..?

or.. the axis is changed when x value become larger than y value..?

Why this happens? How can i fix this?

Answer 1

As said per default meshes in unity have an index buffer of 16-bit (= UInt16) meaning the maximum index is 65535.

If you want to go higher (like with your mesh) you will need to change the Mesh.indexFormat to 32-bit (= UInt32), allowing a maximum index of 4294967295.

Note though that not all GPU support this!