CreateUnityMesh.cs

CreateUnityMesh.cs

        var mesh = new Mesh
        {
            vertices = new Vector3[]
            {
                Vector3.zero, 
                Vector3.right, 
                Vector3.right + Vector3.back,
                Vector3.back,
            },
            uv = new Vector2[]
            {
                new Vector2(0, 0),
                new Vector2(1, 0),
                new Vector2(1, 1),
                new Vector2(0, 1),
            },
            triangles = new int[]
            {
                0, 1, 2,
                2, 3, 0
            }
        };

        gameObject.AddComponent<MeshFilter>().mesh = mesh;
        gameObject.AddComponent<MeshRenderer>();