How to merge trimmed surfaces

I need some help, please! I created a surface out of trimmed patches. Now I would like to merge the edges but nothing works for trimmed edges. I´m not able to loft the surface like I want to so I had to use the patch command an trimm the edges… Anyone some advice?

@jen, you might post the file.


v3_1.7z (73.0 KB)

Upload the .3dm file directly. You can use the vertical arrow icon in the row of icons above where you type your post.

v3_1.3dm (291.4 KB)

Do you want to MergeSrf or Join the surfaces?

MergeSrf doesn’t work with trimmed surfaces due to how the math of NURBS surfaces works.

Join wil work on trimmed surfaces, but only if the adjacent edges are within tolerance of each other. In you file the adjacent edges are not close to each other.

well, at the end I need one closed surface that I can extrude and will be one solid volume. I also tried to “patch” between and create a new surface by lofting the trimmed borders but that will not let me join all polyfurfaces later, couldn´t figure out why. so that´s why I need a way to match both edges of these trimmed surfaces… just really don´t kow how…

A single surface for your geometry will be very difficult or impossible to create.

You can ExtrudeSrf with Solid=Yes the individual surfaces within a polysurface. BooleanUnion the resulting solids to create a single solid.

There is no direct method to match two trimmed edges.

so I did before like you said. Boolean didn´t work. the solids seamed to be right next to each other but they would´t match to be one. that´s why I thought I go back to where the file is now and try to match the edges somehow…
Anyway, thanks a lot for your help and trying!!

@jen, i think doing it with one of the 4 tiles would be easiest. Create a surface and rebuild it, say using 6x6 points and degree 5. Then move the controlpoint U and V rows so the surfaces are constrained outside the trim (where the blue line is in my file). At this area the surface edges need to match so the control points need to constrain it there.

Next turn points on for the surface and move the center control points vertically. If you then Trim with the red curves in my file from top view and the green one in the middle you could finish it by mirroring.

v3_1_c.3dm (347.1 KB)


i was talking about creating a polysurface (surfaces joined together), not using the unjoined surfaces you currently have. Also when Boolean operations don’t work you can always try separately using Trim and/or Split, Delete and Join.

thank you soo much !!!
so may I asked how you build the one surface? Still don´t quite understand how it works so that I´m able to build it on my on.

@jen, building one of the 4 surfaces flat should be easiest, from one corner to the center of the whole part. Then insert rows of controlpoints using _InsertControlPoint where you need them to constrain the surface where it is required. You might turn points on for the example i’ve posted above to understand how i made it.

If you move surface points vertical you’ll need to fiddle a bit with them until it looks as desired. Take care that the surface stays flat where they need to be joined later. Finally _Trim from top starting with the red curves. (I did _ExendSrf the surface before slightly so i get beyond the green line in the middle). Then i trimmed where the blue lines are and mirrored a copy over X, then in front view (No Copy) over X. Then _ArrayPolar with 2 copies…


Thank you soo much for your help!!! really saved my day :slight_smile:
and much easier than I made it in my head :wink: