Subdivide the bicubic surface up to eight times to increase the number of vertices and tangents. Then translate the vertices for a smaller region of the image for more precision. You should warp the surface with a small number of subdivisions to obtain the best results. After applying some deformations to a large portion of the surface, subdivide the surface further and perform deformations on a more localized region of the surface.

To subdivide extended bicubics:

1. From the Extended Bicubic Vertices menu, click Subdivide.

   
   

   You can click the subdivide button up to eight times to further subdivide the surface.

2. Transform the tangents to achieve the effect you want.

To move the reference point:

1. Select the reference point.

   The reference point turns red when selected.

2. Drag the reference point to a new location, or use the X, Y and Z fields to assign a new coordinate for the reference point.

To rotate multiple surface points:

1. Set the reference point values you want to use as the axis of origin using the X, Y, Z Reference Point fields.
2. Select multiple surface points by pressing Ctrl and dragging to select the surface points.
3. From the Edit Mode box, select Rotate.

   A 3D trackball appears on the reference point.

4. Use the 3D trackball to rotate the reference point and selected points.

   All selected points rotate around the reference point.

To scale multiple surface points:

1. Set the reference point values you want to use as the axis of origin using the X, Y, Z Reference Point fields.
2. Select multiple surface points by pressing Ctrl and dragging to select the surface points.
3. From the Edit Mode box, select Scale.
4. Drag in a direction in the image window to scale accordingly.