Working with trimmed Surfaces

Although I know trimmed surface is often a recurrent question. But somehow couldn’t manage find something pertinent. I’d like to experiment different kind of panelling over an trimmed surface. For instance tried playing its panelling tools, but can’t get a “clean” result. It either cuts off the surface, or other bugs that result from it being a trimmed surface. I’d like to play around with 3 kinds of objects on the surface: squared panel (i.e. Panteon Rome ceiling), linear arrays of circular beams (bamboo) that would follow the shape, and another one have short vertical elements descending from a grid on the surface. For all these cases I’d need to figure out to properly subdivide the surface. I spent quite a while trying to find the solution, but even though reaching the point where my brain is baked still can’t figure it out.
Any help will be greatly appreciated! (29.9 KB)

Q.3dm (178.8 KB)

Many of my “paneling” tasks had trimmed and double-curved surfaces as reference. There are many different strategies to approach this problem, and it depends on the pattern to a great extent.
The trick is quite simple. Simply don’t use such a surface for building up the pattern. It only acts as reference for projections as best, for cutting flanges or as a rough indicator. In general, you should define a boundary, because making a proper frame around the projection space usually helps in visually fitting the pattern into the overall shape.

You basically already draw what you should do. The blue curves indicate the pattern flow. Just learn on how to create pattern from a network of curves. As an alternative, you can create a surface above the actual one and use its better aligned iso-curves as reference. There is no plugin required for all this.