Wish for Split: Add "Curve" and "Surface" options in the Command line

Years ago I requested for this improvement of the “Split” command to be made, and now I will repeat my request, because it’s too essential and could speed up the work that involves splitting of models multiple times per day. In fact, many Rhino users are unaware that couple of “hidden” options exist for this tool that are accessible by typing “crv” or “srf” in the Command line, hence they struggle to split certain models the way they want due to inability to combine curves, surface edges and surfaces for the splitting process.


For now, aliases work well - I have ‘tt’ as Trim and ‘ttc’ as ! SelNone _Trim Crv for example.


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Hi Pascal, I’m aware of these hidden options since years, however, I’m pretty sure that the majority of Rhino users have no idea that they even exist. Also, having a 3d mouse makes my workflow slower when I’m forced to type aliases in the Command line. If the “Curve” and “Surface” options where included in the Command line next to the existing “Isocurve” option, they would be much easier to pick with the mouse. And would be visible to all Rhino users. :slight_smile:

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I understand the logic, but in this case, wouldn’t it be better to indicate ( Type Shrink ) to avoid adding too many options in the command line…

Then under Type : Isocure Curve …

This seems to me to be more in line with how Rhino handle sub options in the Cmd Line

Just an idea…

Rodolfo Santos

In contrast to other tools where Rhino should remember a certain option from the Command line, being able to combine different types of geometry (surface, edge, usocurve) to split a model is essential in many cases, this is why having those 3 options shown simultaneously next to each other is more intuitive and easier to use. :slight_smile: Not to mention that it saves mouse clicks.

Makes sense.

My concern was that if you change the rules for one specific tool, why not for all others tools then …
It’s like guessing that one command has more importance than the others and depending on the user needs, this may vary.

But I understand your point of view : direct access & efficiency.

Rodolfo Santos

It’s related to the kind of things one has to do while using a certain tool. For example, splitting with several types of geometry (surface, curve /also used to pick surface edge/, isocurve) that could be quickly changed and combined multiple times while the command is still active requires multiple mouse clicks, this is why a direct access to those options makes more sense. The user basically tells Rhino: “I want you to split this model with these 3 surfaces, these 7 curves, that isocurve and these 2 additional surfaces that I forgot to pick initially. Now be good and do it for me conveniently”. :slight_smile:
On the other hand, tools such as “! _ReplaceEdge” or “! _Extend” only need one option to be pre-selected to complete the command. They also benefit from that by remembering the last option, so that it could be used for the next time within the current session.

I can tell you that is not going to work very well with Isocurves the way it works now. In order to split with Isocurve you need to pick only one surface to be split and that surface needs to stand alone - it can’t be joined to another. After you select the Isocurve option you don’t get to pick crvs or srfs because Rhino wants to know what direction Isocurve you want and what point on the one surface the user wants the isocurve to be located. The same is true of the point option. When you select that option you are only allowed to split one curve at the users chosen points.

If you want to pick some combination of crvs, srfs and edges why not just use the subobject selection?

I’m talking about splitting a surface, not curves. :wink:
On the Isocurve subject. If Rhino asks you for a direction, you just change it and voila. Then the rest options should be visible again. Can’t see anything impossible here.

Thanks Bobi for your thread, after 20 years I learned something new (didn’t know about this hidden “filters”).
A “section” option that allow user to pick two points that define a cutting plane would be useful too (in the same way SplitFace works)


I had no idea either.

“A feature a user doesn’t know about is the same as that feature not existing.”

The Rhino UI hides a lot of features which makes it seem like quite a basic application. It’s good that these user forums exist to show people otherwise, but not everyone who uses Rhino come here.


For this kind of splitting a surface I use one of the following methods:

  1. I preliminary build a plane or a more complex splitting surface. Sometimes I prefer to build a curve and then use it to extrude a history-enabled Extrude surface, because it lets me modify the curve and see if the updated extruded surface has the optimal shape that I need to use as a splitting surface. Or, I simply modify the control points of the splitting surface. I used this method here:

  2. I use the “Geodesic curve” tool, a.k.a. the ! _ShortPath command. It tries to create the shortest curve between two points on the surface.

  3. I also use the “Section” tool, a.k.a. ! _Section, which is very similar to the “Geodesic curve” except that it’s dependent of the current CPlane’s XY-axis and creates a straight projection (when viewed from top view) between two points on the surface.


Are those hidden options implemented in Rhino for Mac ?
Tried in V7 but seems to not react.

My understanding of it is that the message " Select Cutting Object" is the generic option allowing to pick any type of valid cutting object. Then specifying a class of object through options seems not that necessary.

Is this interpretation correct ?

Rodolfo Santos


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