vb : how to make surface to brep?

hi,

I make a vb script that change Triangle surfaces to brep.

this is input Triangle surfaces

but, Output Surfaces(brep) is rectangle surfaces.

why ToBrep method make triangle surfaces to rectangle?

I want to make Triangle Surfaces to Triangle Brep...

on the contrary to this, how to make Brep to surfaces?

here is my method

Private Sub RunScript(ByVal Trisurfaces As List(Of Surface), ByRef A As Object)

Dim BrepTris As New List(Of brep)

For Each Trisurface As surface In Trisurfaces
Dim brepfromsrf As Brep
brepfromsrf = rhino.geometry.Brep.CreateFromSurface(Trisurface)
BrepTris.Add(brepfromsrf)
Next

a = BrepTris

thanks

Replies to This Discussion

Permalink Reply by Mostapha Sadeghipour Roudsari on August 31, 2012 at 9:17pm

Hi Kim,

Are the surfaces trimmed surfaces? Seems "create Brep from surface" untrim the surfaces. If this is the case, then you should first build trimmed surfaces and then use create Brep from surfaces to convert them to Breps.

Regards,

Mostapha

Permalink Reply by Kim Dong Wook on August 31, 2012 at 9:48pm

input surfaces are trimmed surfaces and output surfaces(brep) are untrimmed surfaces...

Permalink Reply by David Rutten on September 1, 2012 at 3:51am

Rhino.Geometry.Surface cannot be trimmed. You need a BrepFace class in order to associate trimming information with a surface. What I think is happening is that Kim is confused by the different usage of "surface" in the Rhino SDK and Grasshopper.

In Grasshopper, there is no data-type specifically for Rhino.Geometry.Surface. What is called a "surface" in Grasshopper, is always a Brep with only a single face. I made this choice because I wanted to have surfaces with trimming data.

So what happens here (I think anyway) is that Kim has a list of Grasshopper surfaces which are in fact trimmed breps with a single face each. When he feeds them into the Script component he uses the Surface typehint, which effectively strips all trimming information from the triangles, resulting in the rectangles. Then the Brep.CreateFromSurface method is no longer able to recover the trimming information, it's too late.

Kim: Use a Brep typehint instead, see if that helps.

David Rutten

david@mcneel.com

Poprad, Slovakia

Permalink Reply by Mostapha Sadeghipour Roudsari on September 1, 2012 at 10:27am

Thank you David for clarification.

Kim! Vincet's code is what I meant by "you should first build trimmed surfaces".

Permalink Reply by Kim Dong Wook on September 6, 2012 at 7:50am

always thanks for your reply.

Permalink Reply by Vicente Soler on September 1, 2012 at 9:26am

You can also construct a triangular surface out of an untrimmed surface by having one of the surface parameters collapse into a singularity.

Permalink Reply by Vicente Soler on September 1, 2012 at 9:56am

The code to achieve this would be something like:

Private Sub RunScript(ByVal x As Brep, ByRef A As Object) Dim p() As point3d = x.DuplicateVertices Dim srf As brep = brep.CreateFromCornerPoints(p(0), p(1), p(2), p(2), doc.ModelAbsoluteTolerance) a = srf.Faces(0).tonurbssurface End Sub

Permalink Reply by Kim Dong Wook on September 6, 2012 at 7:49am

thanks for reply~

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