# Mesh Scripting

## Contents

### Introduction

First of all you have to import the Mesh module:

```
import Mesh
```

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

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')
```

(A list of compatible filetypes can be found under 'Meshes' here.)

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

```
planarMesh = [
# 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],
]
planarMeshObject = Mesh.Mesh(planarMesh)
```

The Mesh-Kernel takes care about creating a topological correct data structure by sorting coincident points and edges together.

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

### Modeling

To create regular geometries you can use the Python script BuildRegularGeoms.py.

```
import BuildRegularGeoms
```

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. To create a toroid, for instance, can be done as follows:

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

The first two parameters define the radiuses 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 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.

```
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
Finally, a full example that computes the intersection between a sphere and a cylinder that intersects the sphere.
import Mesh, BuildRegularGeoms
sphere = Mesh.Mesh( BuildRegularGeoms.Sphere(5.0, 50) )
cylinder = Mesh.Mesh( BuildRegularGeoms.Cylinder(2.0, 10.0, True, 1.0, 50) )
diff = sphere
diff.difference(cylinder)
d = FreeCAD.newDocument()
d.addObject("Mesh::Feature","Diff_Sphere_Cylinder").Mesh=diff
d.recompute()
```

### Examining and Testing

### Write your own Algorithms

### Exporting

You can even write the mesh to a python module:

```
m.write("D:/Develop/Projekte/FreeCAD/FreeCAD_0.7/Mod/Mesh/SavedMesh.py")
import SavedMesh
m2 = Mesh.Mesh(SavedMesh.faces)
```

### Odds and Ends

An extensive (though hard to use) source of Mesh related scripting are the unit test scripts of the Mesh-Module. In this 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.