Convert Part objects to meshes
Converting higher-level objects such as Part shapes to simpler objects such as meshes is a pretty straightforward operation where all faces of a Part object get triangulated. The result of that triangulation (tessellation) is then used to construct a mesh:
import Mesh
obj = FreeCADGui.Selection.getSelection()[0] # a Part object must be preselected
shp = obj.Shape
faces = []
triangles = shp.tessellate(1) # the number represents the precision of the tessellation
for tri in triangles[1]:
face = []
for i in tri:
face.append(triangles[0][i])
faces.append(face)
m = Mesh.Mesh(faces)
Mesh.show(m)
Alternative example:
import Mesh
import MeshPart
obj = FreeCADGui.Selection.getSelection()[0] # a Part object must be preselected
shp = obj.Shape
mesh = FreeCAD.ActiveDocument.addObject("Mesh::Feature", "Mesh")
mesh.Mesh = MeshPart.meshFromShape(
Shape=shp,
LinearDeflection=0.01,
AngularDeflection=0.025,
Relative=False)
Convert meshes to Part objects
Converting meshes to Part objects is a common operation. Very often you will receive 3D data in a mesh format. Meshes are quite practical for representing free-form geometry and big visual scenes, as they are very lightweight. But in FreeCAD we generally prefer higher-level objects, solids, that can carry much more information and allow for curved faces.
Converting meshes to those higher-level objects (handled by the Part Workbench in FreeCAD) is not an easy operation. Meshes can contain thousands of triangles (for example when generated by a 3D scanner), and solids made of the same number of faces would be extremely difficult to manipulate. So you generally want to optimize the object when converting.
FreeCAD currently offers two methods to convert meshes to Part objects. The first method is a simple, direct conversion without any optimization:
import Mesh
import Part
mesh = Mesh.createTorus()
shape = Part.Shape()
shape.makeShapeFromMesh(mesh.Topology, 0.05) # the second arg is the tolerance for sewing
solid = Part.makeSolid(shape)
Part.show(solid)
The second method offers the possibility to consider mesh facets co-planar when the angle between them is under a certain value, reducing the number of faces in the final result:
import Mesh
import Part
import MeshPart
obj = FreeCADGui.Selection.getSelection()[0] # a Mesh object must be preselected
mesh = obj.Mesh
segments = mesh.getPlanarSegments(0.00001) # use rather strict tolerance here
faces = []
for i in segments:
if len(i) > 0:
# a segment can have inner holes
wires = MeshPart.wireFromSegment(mesh, i)
# we assume that the exterior boundary is that one with the biggest bounding box
if len(wires) > 0:
ext = None
max_length=0
for i in wires:
if i.BoundBox.DiagonalLength > max_length:
max_length = i.BoundBox.DiagonalLength
ext = i
wires.remove(ext)
# all interior wires mark a hole and must reverse their orientation, otherwise Part.Face fails
for i in wires:
i.reverse()
# make sure that the exterior wires comes as first in the list
wires.insert(0, ext)
faces.append(Part.Face(wires))
solid = Part.Solid(Part.Shell(faces))
Part.show(solid)
This page is retrieved from https://wiki.freecad.org/Mesh_to_Part