How to divide B-Spline surface or SmartSurface along rule lines, resulting in individual surfaces.
This can be done with the Project Trim tool's Impose Onto setting. Here's how:
1. Extract the rule lines onto the surface using the Extract Iso-parametric lines tool, set to Multiple Curves.
2. Select these Iso-lines in a selection set.
3. Select the Project Trim tool, Direction: Orthogonal, Output Mode: Impose Onto. Select the surface and accept.
4. Drop the resulting SmartSurface with the Drop tool with Solids toggled on and set To Surfaces.