Mesh Scripting

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Introduction

To get access to the Mesh module you have to import it first:

import Mesh

Creation

To create an empty mesh object just use the standard constructor:

mesh = Mesh.Mesh()

You can also create an object from a file:

mesh = Mesh.Mesh("D:/temp/Something.stl")

Or create it out of a set of triangles described by their corner points:

triangles = [
# triangle 1
[-0.5000, -0.5000, 0.0000], [0.5000, 0.5000, 0.0000], [-0.5000, 0.5000, 0.0000],
#triangle 2
[-0.5000, -0.5000, 0.0000], [0.5000, -0.5000, 0.0000], [0.5000, 0.5000, 0.0000],
]
meshObject = Mesh.Mesh(triangles)
Mesh.show(meshObject)

The Mesh-Kernel takes care of creating a topologically correct data structure by sorting coincident points and edges.

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Modeling

To create regular geometries you can use the Python module BuildRegularGeoms:

import BuildRegularGeoms

This module provides methods to define simple rotation bodies like spheres, ellipsoids, cylinders, toroids and cones. And it also has a method to create a simple cube. A toroid, for instance, can be created as follows:

t = BuildRegularGeoms.Toroid(8.0, 2.0, 50) # list with several thousands triangles
m = Mesh.Mesh(t)
Mesh.show(m)

The first two parameters define the radii of the toroid and the third parameter is a sub-sampling factor for how many triangles are created. The higher this value the smoother the mesh.

The Mesh module also provides three Boolean methods: union(), intersection() and difference():

m1, m2              # are the input mesh objects
m3 = Mesh.Mesh(m1)  # create a copy of m1
m3.unite(m2)        # union of m1 and m2, the result is stored in m3
m4 = Mesh.Mesh(m1)
m4.intersect(m2)    # intersection of m1 and m2
m5 = Mesh.Mesh(m1)
m5.difference(m2)   # the difference of m1 and m2
m6 = Mesh.Mesh(m2)
m6.difference(m1)   # the difference of m2 and m1, usually the result is different to m5

Here is an example that creates a pipe using the difference() method:

import FreeCAD, Mesh, BuildRegularGeoms
cylA = Mesh.Mesh(BuildRegularGeoms.Cylinder(2.0, 10.0, True, 1.0, 36))
cylB = Mesh.Mesh(BuildRegularGeoms.Cylinder(1.0, 12.0, True, 1.0, 36))
cylB.Placement.Base = (FreeCAD.Vector(-1, 0, 0)) # move cylB to avoid co-planar faces
pipe = cylA
pipe = pipe.difference(cylB)
pipe.flipNormals() # somehow required
d = FreeCAD.ActiveDocument
d.addObject("Mesh::Feature", "Pipe").Mesh = pipe
d.recompute()

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Exporting

You can even write a mesh to a python module:

import os
path = os.environ.get("APPDATA") + "/FreeCAD/Macro/SavedMesh.py"
m.write(path)
import SavedMesh
m2 = Mesh.Mesh(SavedMesh.faces)

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Notes

An extensive, though hard to use, source of mesh related scripting are the unit test scripts of the Mesh module. In these unit tests literally all methods are called and all properties/attributes are tweaked. So if you are bold enough, take a look at the Unit Test module.

See also: Mesh API.

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