Mesh Scripting: Difference between revisions

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First of all you have to import the Mesh module:
To get access to the {{incode|Mesh}} module you have to import it first:


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==Creation and loading== <!--T:3-->
After that you have access to the Mesh module and the Mesh class which facilitate the functions
of the FreeCAD C++ Mesh-Kernel.

==Creation and Loading== <!--T:3-->
To create an empty mesh object just use the standard constructor:
To create an empty mesh object just use the standard constructor:


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You can also create an object from a file
You can also create an object from a file:


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{{Code|code=
{{Code|code=
mesh = Mesh.Mesh('D:/temp/Something.stl')
mesh = Mesh.Mesh("D:/temp/Something.stl")
}}
}}
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(A list of compatible filetypes can be found under 'Meshes' [[Feature_list#Key features|here]].)


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{{Code|code=
{{Code|code=
planarMesh = [
triangles = [
# triangle 1
# triangle 1
[-0.5000, -0.5000, 0.0000], [0.5000, 0.5000, 0.0000], [-0.5000, 0.5000, 0.0000],
[-0.5000, -0.5000, 0.0000], [0.5000, 0.5000, 0.0000], [-0.5000, 0.5000, 0.0000],
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[-0.5000, -0.5000, 0.0000], [0.5000, -0.5000, 0.0000], [0.5000, 0.5000, 0.0000],
[-0.5000, -0.5000, 0.0000], [0.5000, -0.5000, 0.0000], [0.5000, 0.5000, 0.0000],
]
]
planarMeshObject = Mesh.Mesh(planarMesh)
meshObject = Mesh.Mesh(triangles)
Mesh.show(planarMeshObject)
Mesh.show(meshObject)
}}
}}
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The Mesh-Kernel takes care about creating a topologically correct data structure by sorting
The Mesh-Kernel takes care of creating a topologically correct data structure by sorting coincident points and edges.
coincident points and edges together.

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Later on you will see how you can test and examine mesh data.


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To create regular geometries you can use the Python script {{FileName|BuildRegularGeoms.py}}.
To create regular geometries you can use the Python module {{incode|BuildRegularGeoms}}:


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This script 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.
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:
A toroid, for instance, can be created as follows:


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t = BuildRegularGeoms.Toroid(8.0, 2.0, 50) # list with several thousands triangles
t = BuildRegularGeoms.Toroid(8.0, 2.0, 50) # list with several thousands triangles
m = Mesh.Mesh(t)
m = Mesh.Mesh(t)
Mesh.show(m)
}}
}}
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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 and the lower the coarser the body is.
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 class provides a set of boolean functions that can be used for modeling purposes. It provides union, intersection and difference of two mesh objects.
The {{incode|Mesh}} module also provides three Boolean methods: {{incode|union()}}, {{incode|intersection()}} and {{incode|difference()}}:


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An extensive (though hard to use) source of Mesh related scripting are the unit test scripts of the Mesh-Module.
An extensive, though hard to use, source of mesh related scripting are the unit test scripts of the {{incode|Mesh}} module.
In this unit tests literally all methods are called and all properties/attributes are tweaked.
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 [https://github.com/FreeCAD/FreeCAD/blob/master/src/Mod/Mesh/App/MeshTestsApp.py Unit Test module].
So if you are bold enough, take a look at the [https://github.com/FreeCAD/FreeCAD/blob/master/src/Mod/Mesh/App/MeshTestsApp.py Unit Test module].


Revision as of 10:45, 1 June 2020

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Introduction

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

import Mesh

Creation and loading

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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Mesh
Power user documentation
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