Microtile derivatives

[markriegler]

Of all the available microtiles, only a couple have correctly implemented derivatives w.r.t. the tile parameters. Some don't have it and some show wrong derivatives (compared to derivatives obtained using finite differences).

Here is a list of tiles which have these wrong derivatives:

• Chi
• EllipsVoid
• CubeVoid
• InverseCross3D

[markriegler]

• EllipsVoid and CubeVoid seem to cause trouble because of the rotation matrices.
• The problem with Chi and InverseCross3D might be due to the tile's patches (partially) having degree 2

[markriegler]

The problems with Chi and InverseCross3D didn't have to anything with the degree. The derivatives are only dependent on the control points since they are Bezier patches