Wish: Failed split to become smarter and more user-friendly

Quite often Rhino fails to make a successful split of a surface or a polysurface, and the Command line warning says: “Split failed, objects may not intersect or intersections may not split object.”
Currently, right after the aforementioned warning message, Rhino will “forget” and deselect all the cutting objects that were chosen for the “Split” command, forcing the user to selected them again. Rhino would be much more user-friendly if it lets you continue adding more cutting objects after the warning message, which indicated that the last selection was not enough to make a proper split. Being able to add extra cutting objects while the previously selected ones are still active would save a lot of time, and reduce the mouse clicks and camera manipulation in cases with multiple cutting objects.

Here is a usual example from my workflow. Lets say that my goal is to split a surface via a combination of 50 surface edges, curves and surfaces. If I miss to select some tiny 1 mm cutting object, Rhino warns me with the “Split failed, objects may not intersect or intersections may not split object.” and unfortunately deselects the cutting objects that took me long time to pick one by one, forcing me to spend a lot of time to select them again including the one tiny cutting object I missed to pick initially.

So, I see two good possible solutions here:

  1. Keep the last selection of cutting objects selected after the warning message, even though they failed to split the desired object(a).
  2. Add a Command line option called “Save selected cutting objects”, so that the user could click on in and Rhino will automatically save that as a one-click selection for future split operations.

I think that the 1st solution is easier to implement by the programmers.

My second proposition is to finally add the HIDDEN options to split via curves or surfaces, which could be evoked by typing “crv” or “srf” in the Command line, respectively! I already asked for this enhancement in several topics in the past, but so far these options are still hidden and many Rhino users even don’t know about their existence, resulting into lots of struggles with failed Trim and Split operations, and far less enjoyable experience overall. As we all know, splitting a surface by adjacent surfaces (especially fillets tangent to the surface to be split) sometimes fails and the only solution is to either use the hidden “crv” option or to preliminary duplicate the surface edge and use the output curve. Having visible clickable options “curve” and “surface” in the command line all the time during the Split and Trim commands will make the experience of many Rhino users so much easier.


What are the “hidden options”? What do they do and how are they used?

I’m with you!
Making the crv filter selection a visible option for trim and split would be amazing!

Teaching users this trick is hard.

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I made a short video for you to show how the hidden options are evoked by typing “crv” or “srf” in the Command line and what’s the benefit of knowing their existence. They both help in situations where the “Split” and “Trim” commands fail for some reason.

adding (or removing) additional cutters would be great. for both command _split and _trim

I would love another enhancement:

chained Isocurves
currently splitting with Isocurves only works for a single surface.
I would love to split across multiple surfaces by selecting a starting Isocurve, and the option should select the isocurves that fits best over an edge…and also swapping U-V …
a very simple example:

the workflow could be like this:
select objects to split (multiple surfaces, polysurfaces)
option Isocurve
option Shrink = yes
option chained Isocurve
→ select starting surface
→ select first Isocurve … auto selection

or for multiple surfaces:
select isocurve on first surface
select isocurve on next surface

:heart: :broken_heart:

kind regards -tom

“crv” and “srf” are not options of the Trim and Split commands. Instead they are one shot selection filters which work with any command when an object needs to be selected.

Start a command such as Move, Copy, Rebuild, Trim, Split, etc.

When the command asks for an object type crv or srf and enter. Only curves or surfaces can be selected as the object(s).

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similarly i would like to select chain of curves in arraycrv command

What do you mean by “chain of curves”? How is that different from a polycurve?

polysurface edges for instance. now you can only select one subobject=edge, but you want your array to follow multiple edges

Chained isocurves
How should this work here ?

the behaviour could be similar to
continuety can be position or tangent / max angle.
u or v selected by best match (smaller angle)

for this corner:
with option tangent - no chain selected, additional isocurve-selection necessary.
with option position - or with a big tangent-tolerance-angle - closest Point, best fit u or v

and as it is an option - if their is any doubt, it should do nothing - better then something wrong.