Hi Quirin,

this is essentially what SubSurface does. If you want a custom trim
edge (something which is not possible with curves since the 'edge' of
a curve is always a single parameter) you somehow have to provide
additional information.
Here are some examples of how this could possibly be solved:

1) Trim a BRep with a closed curve, and keep the parts inside/outside
the curve region
2) Trim a BRep with a closed brep, and keep the parts inside/outside
the brep volume
3) Trim a BRep and supply an extra point (or multiple points) which is
on or near the section you wish to keep

--
David Rutten
[email protected]
Robert McNeel & Associates


On Mar 6, 2:19 pm, quirin <[email protected]> wrote:
> just an idea, but can't you use the curve parameters to decide which
> part to trim.
> when i trim a curve in rhino with parameters ranging from "0 to x" the
> result is either "0 to y" or "y to x"...
> but this would only work for curves as surfaces keep the untrim
> information.
>
> quirin
>
> On Mar 6, 12:48 pm, KCCaine <[email protected]> wrote:
>
> > Without knowing exactly what jojo had in mind I can add the following,
> > which might help him/her get a clearer understanding (I know it would
> > help me!):
>
> > When you capture a trimmed surface into grasshopper is does come in as
> > described by Rhino. If you generate a grid of UV points on this
> > surface these populate over the trimmed surface. However, if you try
> > to extract an isoparametric subset of the same surface this operation
> > works on an untrimmed surface. This is also true of the surface box
> > command. This seems much the same as if you were to rebuild the
> > surface in Rhino, but the Rhino rebuild function allows you to
> > maintain the surface as trimmed. Is it possible to have a retrim (true/
> > false) option on these types of operations?
>
> > Thx
>
> > KwaiChang
>
> > On Mar 6, 10:46 am, David Rutten <[email protected]> wrote:
>
> > > Ok, the answer is no.
>
> > > Trimming is always tricky in 2D because it's not obvious which parts
> > > are meant to be kept.
> > > I'll add a Split component to multiple breps and breps+curves, but I'm
> > > not sure how a Trim component would work.
>
> > > If you have any ideas, I'd love to hear them.
>
> > > --
> > > David Rutten
> > > [email protected]
> > > Robert McNeel & Associates
>
> > > On Mar 5, 11:26 pm, CMRHM <[email protected]> wrote:
>
> > > > Sorry for not asking clearly. I mean trimming two interconnected
> > > > surfaces. There is no custom curves involved.
>
> > > > But may be you provided the answer already, I will try remaping and
> > > > projecting tonight.
>
> > > > On Mar 5, 4:19 pm, David Rutten <[email protected]> wrote:
>
> > > > > You can copy trims fro another surface, either by remapping the curves
> > > > > onto the new UV domain or by projecting the curves, but I haven't
> > > > > added a component yet that will allow you to trim with custom curves.
>
> > > > > Using the Solid components is the closest you can get at the moment.
>
> > > > > --
> > > > > David Rutten
> > > > > [email protected]
> > > > > Robert McNeel & Associates
>
> > > > > On Mar 5, 10:55 pm, CMRHM <[email protected]> wrote:
>
> > > > > > Hi, David:
>
> > > > > > Is there a component in GH for trimming a surface? I can't find it. 
> > > > > > It
> > > > > > looks SubSrf is close, but it is not.
>
> > > > > > Thanks.
>
> > > > > > On Mar 5, 2:11 pm, David Rutten <[email protected]> wrote:
>
> > > > > > > Hi Jojo,
>
> > > > > > > 1) I don't follow. If you reference a trimmed surface in 
> > > > > > > Grasshopper
> > > > > > > it gets importer as a trimmed surface. The geometry is not 
> > > > > > > altered in
> > > > > > > the slightest. This is probably one of those: "I know that you 
> > > > > > > believe
> > > > > > > you understand what you think I said, but I'm not sure you realize
> > > > > > > that what you heard is not what I meant." moments...
>
> > > > > > > 2) Sorry, can't do. The geometry that Grasshopper generates is 
> > > > > > > drawn
> > > > > > > on top of the Rhino model. I.e. Rhino has no idea it all exists 
> > > > > > > and
> > > > > > > thus is unable to include it in selection logic. Someday we might 
> > > > > > > be
> > > > > > > able to get around this, but it will almost certainly involve a
> > > > > > > special working mode/command.
>
> > > > > > > 3) I'm working on Undo/Redo. The project got shelved a while ago 
> > > > > > > as I
> > > > > > > was trying to get these damn data-trees up and running.
>
> > > > > > > --
> > > > > > > David Rutten
> > > > > > > [email protected]
> > > > > > > Robert McNeel & Associates
>
> > > > > > > On Mar 5, 5:20 pm, jojowasmydog <[email protected]> wrote:
>
> > > > > > > > Firstly, I have use grasshoppers for two school projects and I 
> > > > > > > > totally
> > > > > > > > in love with the program! Thanks for the great work! If it 
> > > > > > > > could be
> > > > > > > > better, I would suggest this possible options.
>
> > > > > > > > 1) Recognization of Trim surface: when surface is trim in rhino,
> > > > > > > > grasshopper does not recognice and reconstruct the uv curve 
> > > > > > > > according
> > > > > > > > to the new geometry of the surface, it would be good if there 
> > > > > > > > is a
> > > > > > > > buttom to make grasshopper recognice the end of the trim edge.
>
> > > > > > > > 2) selecting in rhino and feekback to grashopper: quite often, 
> > > > > > > > when a
> > > > > > > > project gets bigger, I really wish I can select from rhino and 
> > > > > > > > know
> > > > > > > > which line is drawn in grasshopper.
>
> > > > > > > > 3) Record history inside grasshopper: this is a bit like the 
> > > > > > > > undo
> > > > > > > > function but a bit more complicated in a sense. I try Generative
> > > > > > > > component and they have this already. Would be great if 
> > > > > > > > grasshopper
> > > > > > > > can undo. And also have a record history.- Hide quoted text -
>
> > > - Show quoted text -

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