Mesh to Part/pl: Difference between revisions

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==Konwersja siatki do obiektów środowiska Część==
==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 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.

Revision as of 09:15, 18 December 2022

Konwersja obiektów środowiska Część do siatek

Konwersja obiektów wyższego poziomu takich jak część środowiska Część, na prostsze obiekty takie jak siatka środowiska Projekt Siatki jest całkiem prostą operacją, gdzie wszystkie ściany obiektu Część są triangulowane. Wynik tej triangulacji (teselacji) jest następnie używany do skonstruowania siatki:

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)

Przykład alternatywny:

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)

Konwersja siatki do obiektów środowiska Część

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)