Trimmed surfaces become untrimmed surfaces through c# or python script

Scripting
,
1

Hello,

I would like to filter out surfaces whose air is less than a given value, for example y =2 m2 (like the green surface in the figure). I tried the scripts in C# and Python, it works but I get untrimmed surfaces instead of trimmed surfaces. With the item operator (for example i=101) I can find the trimmed surfaces but it boring and takes a lot of time each time the geometry changes.

You will find attached the rhino and grasshopper file to clearly see my problem.

with C#
private void RunScript(List x, double y, ref object A)
{
List filteredSurfaces = new List();
foreach (Brep brep in x)
{
{double area = brep.GetArea();
if (area < y)
{
filteredSurfaces.Add(brep.Surfaces[0]);
}
}
}
A = filteredSurfaces;
}

Thank you in advance for your help

filter_surface.3dm (1.0 MB)
filter_surface.gh (19.1 KB)

question_untrimmedsurface
question_untrimmedsurface1269Ă—456 119 KB

2

Hi @msgatrong, you likely want to iterate brep.Faces, measure the face Area and then filter out brep faces. A brep.Surface points to the underlying (untrimmed) surface of a brep face.

filter_by_brep_face_area.gh (10.9 KB)

_
c.

3

Thank you for your suggestion. I rewrote the script but it doesn’t work the function “brep.Faces[i].GetArea()” to get the air from the faces

private void RunScript(List x, double y, ref object A)
{
List filteredSurfaces = new List();
foreach (Brep brep in x)
{
int imax = brep.Faces.Count;
Console.WriteLine(“number of faces {imax}”);
for (int i = 0; i < imax ; i += 1)
{double area = brep.Faces[i].GetArea();
if (area < y)
{
filteredSurfaces.Add(brep.Faces[i]); //
}
}
}
A = filteredSurfaces;
}

4

Hi @msgatrong, GetArea() accepts breps not brep faces. You can get the area without converting a brep face to a brep, see below python example.

filter_by_brep_face_area_py.gh (14.1 KB)

_
c.

1 Like
5

You need to first convert brep.Faces[i] into a Brep with a single face using the method brep.Faces[i].DuplicateFace(False). The brep that DuplicateFace returns can be used to get area.

A Brep with a single face is what you are calling a “trimmed surface” . There is no such thing as a surface in a RhinoCommon document. There are only Breps. If a Brep has more than one face Rhino users call it a polysurface and if it has only one face it is called a surface (either trimmed or untrimmed).

After running your area test you may want to add the Brep that DuplicasteFace gave you to your list rather than the BrefFace.

1 Like
6

This also works for me if you want to use .DuplicateFace and .GetArea():

#! python 2
import Rhino

def FilterBrepFaces(brep, y):
    faces = []
    for i, face in enumerate(brep.Faces):
        area = brep.Faces[i].DuplicateFace(False).GetArea()
        if area < y:
            faces.append(face)
    return faces

a = FilterBrepFaces(brep, y)

it filters out brep faces not breps though. I guess this is what was asked for in the OP.

filter_by_brep_face_area_py.gh (13.3 KB)

_
c.

1 Like
7

it works, thank you very much for your help @clement @jim