Create simple mesh

gistfile1.cs

static void Create()
{
    float x = 512.0f;
    float y = 341.0f;

    Mesh mesh = (Mesh)AssetDatabase.LoadAssetAtPath("Assets/UI/SimpleMesh.asset", typeof(Mesh));
    if( mesh == null)
    {
        mesh = new Mesh();
        mesh.name = "SimpleMesh";
        float vx = x * 0.5f, vy = y * 0.5f;
        mesh.vertices = new Vector3[]{
            Vector3.left * vx + Vector3.up * vy,
            Vector3.right * vx + Vector3.up * vy,
            Vector3.right * vx + Vector3.down * vy,
            Vector3.left * vx + Vector3.down * vy
        };

        mesh.triangles = new int[]{
            0, 1, 2,
            2, 3, 0
        };

        mesh.uv = new Vector2[]{
            new Vector2(1.0f, 1.0f),
            new Vector2(0.0f, 1.0f),
            new Vector2(0.0f, 0.0f),
            new Vector2(1.0f, 0.0f)
        };

        mesh.RecalculateNormals ();
        mesh.RecalculateBounds ();
        mesh.Optimize ();
        
        AssetDatabase.CreateAsset(mesh, "Assets/UI/SimpleMesh.asset");
        AssetDatabase.SaveAssets();
    }
    mesh.RecalculateBounds();
}