duck

MeshFilter meshFilter = AddComponent<MeshFilter>();
Mesh mesh = new Mesh();

Vector3[] verts = new Vector3[] {
    new Vector3(0, 0, 0),
    new Vector3(1, 0, 0),
    new Vector3(1, 0, 1),
    new Vector3(0, 0, 1)
};

int[] tris = new int[] { 0, 2, 1, 3, 2, 0 };

Vector2[] uv1s = new Vector2[] {
    new Vector2(0, 0),
    new Vector2(1, 0),
    new Vector2(1, 1),
    new Vector2(0, 1)
};


// Assign mesh properties
mesh.vertices = verts;
mesh.uv = uv1s;
mesh.triangles = tris;
mesh.RecalculateNormals();
mesh.RecalculateBounds();
meshFilter.mesh = planeMesh;