how to subdivide a surface using Python script?

Replies to This Discussion

Permalink Reply by Grasshope on September 18, 2015 at 1:57am

Dear buggers, advice is greatly appreciated! Thanks!

Permalink Reply by Anton Szilasi on September 18, 2015 at 7:30am

Hi Grasshope,

While I didn't write that component myself. You need the RhinoCommon Mesh.CreateFromBrep method 

search for it in the RhinoCommon - http://4.rhino3d.com/5/rhinocommon/

http://4.rhino3d.com/5/rhinocommon/

Permalink Reply by Mostapha Sadeghipour Roudsari on September 22, 2015 at 4:32pm

Hi Grasshoppe,

Anton is right. You just need to set a number of meshing parameters based on the gridSize.

Here is the sample code that you can find in Honeybee_Generate Test Points:

https://github.com/mostaphaRoudsari/Honeybee/blob/master/src/Honeyb...

Mostapha

Permalink Reply by Grasshope on September 22, 2015 at 9:20pm

Thank you Anton and Mostapha!

I did a brute force "copy and paste" test of the following code, and it didn't work with the warning of unable to determine the length of the brep objects.

I'm sure I get it wrong in this way, and I hope you can point out how to correct the errors.

import Rhino as rc
import Grasshopper.Kernel as gh
from itertools import chain
import System.Threading.Tasks as tasks
import rhinoscriptsyntax as rs

mesh = []

def createMesh(brep, gridSize):
    ## mesh breps
    def makeMeshFromSrf(i, inputBrep):
        try:
            mesh[i] = rc.Geometry.Mesh.CreateFromBrep(inputBrep, meshParam)[0]
            inputBrep.Dispose()
        except:
            print 'Error in converting Brep to Mesh...'
            pass

    # prepare bulk list for each surface
    mesh = [None] * len(brep)

    # set-up mesh parameters for each surface based on surface size
    meshParam = rc.Geometry.MeshingParameters.Default
    meshParam.MaximumEdgeLength = gridSize
    meshParam.MinimumEdgeLength = gridSize
    meshParam.GridAspectRatio = 1

    for i in range(len(mesh)): makeMeshFromSrf(i, brep[i])
    
    return mesh

createMesh(brep, 0.1)

Attachments:

• brepToMesh_v001.gh, 4 KB

Permalink Reply by Stephen Maher on September 23, 2015 at 7:32am

Grasshope,

Make sure you have input parameter "brep" set to 'List Access' and Type Hint 'Brep' (see screen capture below). I've also added a "gridSize" input parameter so you can control the number of mesh faces.

Hope this helps.

/SPM

Permalink Reply by Stephen Maher on September 23, 2015 at 7:33am

File attached.

Attachments:

• brepToMesh_v001_SPM.gh, 4 KB

Permalink Reply by Grasshope on September 29, 2015 at 11:46pm

Thank very much, Stephen!

I found that unexploded Brep object will not be properly processed by the code: only the first surface within the Brep object will be converted to a mesh.

Can you kindly advise the rhinoscript to explode a Brep surface?

Thank you!

Attachments:

• GhPython_v005.gh, 36 KB

Permalink Reply by Stephen Maher on September 30, 2015 at 12:32pm

The easiest solution is to use the [Deconstruct Brep] component and plug in the output faces into Python. You would have to do this for the [Honeybee_Generate Test Points] component as well.

Concerning your second question below, that has to do with the way we call the function. In the Honeybee component, you will notice that Mostapha creates a new list from 'createMesh' and passes that through another function as an argument. So the organization is a bit different from what you're doing.

Hope this helps.

/SPM

Permalink Reply by Anton Szilasi on September 30, 2015 at 12:47pm

Hi Grasshope

Is this what you are looking for? Check out the component Brep to Mesh

Cheers,

Anton

Attachments:

• BreptoMesh AJZ 30.9.2015.gh, 40 KB

Permalink Reply by Grasshope on September 30, 2015 at 9:55am

Hi Stephen, 

I also wonder why in your GH file the brep node must be set as "List Access" to take a group of Breps, whereas in Mostapha's Honeybee_Generate Test Points component, the _testSurface node set as "Item Access" can take a group of Brep as input using the same Python code...