Split face


I want split this BrepFace into 3 BrepFaces

I can get the vertical split curve from the wired model.

I’ve tried split using BrepFace.Split function, but I can’t get the result that I need.

I’m working with rhinoCommon and c#


It would help if you could post the code you use that is not working for you…

I try split the face three ways:

if (!face.IsPlanar())
    // 1
    // split is empty
    Surface[] split = face.Split(0, 1);
    // 2
    // wired contains all vertical curves from face model 
    Curve[] wired = face.ToBrep().GetWireframe(1).Where(c => c.PointAtStart.Z != c.PointAtEnd.Z).ToArray<Curve>();
    // The brep is a horizontal brep
    Brep split2 = face.Split(wired, 1);

    // 3
    // idem case 2
    Curve[] iso = face.TrimAwareIsoCurve(0, 1);
    Brep split3 = face.Split(iso, RhinoDoc.ActiveDoc.ModelAbsoluteTolerance);

In case 1 you use the split along isocurve at parameter value of 1. Maybe the value of 1 is not in the domain of the surface underlying the face, or parameter of 1 only available outside trimmed regions.

In case 2, you use a tolerance of 1, which may be a bit large.

In case 3, again you use an iso curve at parameter value 1. Are you sure that the curve is on the surface?

Sorry, but I don’t understand your responses:

Case 1: How Can I get the correct second parameter?

Case 2: I try with lower tolerance values but not get the desired result

Can you give me an example of how Split the face into 3 segments?


any idea?

A surface has two parameters: U and V (0 and 1). These parameters have domains, within which they describe the surface.

If you say face.Split(0,1) you split the face at U-parameter value of 1. But, it is not at all clear that the value of 1 is inside the U-domain, and if it is in the U-domain that it is “visible” (i.e. not trimmed).

You must first determine the value of the parameter at which you want to split.

But, how I can set the value parameter?

In the next image

I can get the vertical curve to split the surface in two parts, but I don’t know how call the split function

The command below works on the file attached. Can you share your file with the surface that does not want to be split?

ObjRef sRef;
Result res = RhinoGet.GetOneObject("Select brep-face to split", false, ObjectType.Surface, out sRef);
if (res != Result.Success)
    return res;

BrepFace face = sRef.Surface() as BrepFace;
if (null == face)
    return Result.Failure;

Curve[] wired = face.ToBrep().GetWireframe(1).Where(c => c.PointAtStart.Z != c.PointAtEnd.Z).ToArray();

Brep splitted = face.Split(wired, doc.ModelAbsoluteTolerance);
if (null != splitted)

return Result.Success;

FaceSplit.3dm (29.3 KB)

1 Like

Can you explain this row for me?
What does it do and how does it work? :slight_smile:

I do it differently like extruding the curve first so i have a srf that splits them but a crv would be way better and faster.
I’m using vb.net but I dont understand the Where(c =&gt; c.PointAtStart.Z != c.PointAtEnd.Z) part.

Just see you dont use curves to split but use the wireframe. Its still early i Guess xD

This is taken exactly from the OP’s code, where for this specific case he was interested in the vertical lines.

Hi menno.

Brep splitted = face.Split(wired, doc.ModelAbsoluteTolerance);

Brep splitted is a polysurface, and from rhino, if I exec explode command, splitted is divided in 3 segments. The result that I need

But,from code, I don’t know how explode splitted

and jordy1989, the line

Curve[] wired = face.ToBrep().GetWireframe(1).Where(c => c.PointAtStart.Z != c.PointAtEnd.Z).ToArray();

returns an array with all vertical curves that composing the face model.

Ah, I see.

Try this:

foreach(BrepFace f in splitted.Faces)
    doc.Objects.AddBrep(f.DuplicateFace(false)); // duplicate face will create a separate brep of each face
1 Like

Yeah!! it works!!!

Thank you very much!

I owe you a beer … or several !! =)

EDIT: the bucle is:

foreach(BrepFace f in splitted.Faces)
    doc.Objects.AddBrep(f.DuplicateFace(false)); // duplicate face will create a separate brep of each face

Excellent. Glad I could help - it took a while for me to understand your needs.