Mesh to Part/tr: Difference between revisions
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{{docnav|Topological data scripting|Scenegraph}} |
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{{TOCright}} |
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⚫ | Converting higher-level objects such as [[ |
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{{Code|code= |
{{Code|code= |
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#let's assume our document contains one part object |
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import Mesh |
import Mesh |
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obj = FreeCADGui.Selection.getSelection()[0] # a Part object must be preselected |
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shp = obj.Shape |
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faces = [] |
faces = [] |
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shape = FreeCAD.ActiveDocument.ActiveObject.Shape |
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triangles = |
triangles = shp.tessellate(1) # the number represents the precision of the tessellation |
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for tri in triangles[1]: |
for tri in triangles[1]: |
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face = [] |
face = [] |
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for i in |
for i in tri: |
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face.append(triangles[0][i]) |
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face.append(triangles[0][vindex]) |
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faces.append(face) |
faces.append(face) |
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m = Mesh.Mesh(faces) |
m = Mesh.Mesh(faces) |
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Mesh.show(m) |
Mesh.show(m) |
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}} |
}} |
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Sometimes the triangulation of certain faces offered by OpenCascade is quite ugly. If the face has a rectangular parameter space and doesn't contain any holes or other trimming curves you can also create a mesh on your own: |
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Alternative example: |
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{{Code|code= |
{{Code|code= |
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import Mesh |
import Mesh |
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import MeshPart |
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def makeMeshFromFace(u,v,face): |
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(a,b,c,d)=face.ParameterRange |
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pts=[] |
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for j in range(v): |
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for i in range(u): |
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s=1.0/(u-1)*(i*b+(u-1-i)*a) |
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t=1.0/(v-1)*(j*d+(v-1-j)*c) |
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pts.append(face.valueAt(s,t)) |
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obj = FreeCADGui.Selection.getSelection()[0] # a Part object must be preselected |
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shp = obj.Shape |
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for j in range(v-1): |
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for i in range(u-1): |
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mesh.addFacet(pts[u*j+i],pts[u*j+i+1],pts[u*(j+1)+i]) |
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mesh.addFacet(pts[u*(j+1)+i],pts[u*j+i+1],pts[u*(j+1)+i+1]) |
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return mesh |
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mesh.Mesh = MeshPart.meshFromShape( |
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Shape=shp, |
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LinearDeflection=0.01, |
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AngularDeflection=0.025, |
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Relative=False) |
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}} |
}} |
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⚫ | Converting |
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⚫ | 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. |
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⚫ | Converting meshes to those higher-level objects (handled by the [[Part |
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⚫ | Converting meshes to those higher-level objects (handled by the [[Part_Workbench|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. |
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{{Code|code= |
{{Code|code= |
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import Mesh |
import Mesh |
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import Part |
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mesh = Mesh.createTorus() |
mesh = Mesh.createTorus() |
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shape = Part.Shape() |
shape = Part.Shape() |
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shape.makeShapeFromMesh(mesh.Topology,0.05) # the second arg is the tolerance for sewing |
shape.makeShapeFromMesh(mesh.Topology, 0.05) # the second arg is the tolerance for sewing |
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solid = Part.makeSolid(shape) |
solid = Part.makeSolid(shape) |
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Part.show(solid) |
Part.show(solid) |
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}} |
}} |
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The second method offers the possibility to consider mesh facets |
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: |
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{{Code|code= |
{{Code|code= |
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import Mesh |
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# let's assume our document contains one Mesh object |
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import |
import Part |
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import MeshPart |
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obj = FreeCADGui.Selection.getSelection()[0] # a Mesh object must be preselected |
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faces = [] |
faces = [] |
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for i in segments: |
for i in segments: |
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if len(i) > 0: |
if len(i) > 0: |
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# a segment can have inner holes |
# a segment can have inner holes |
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wires = MeshPart.wireFromSegment(mesh, i) |
wires = MeshPart.wireFromSegment(mesh, i) |
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# we assume that the exterior boundary is that one with the biggest bounding box |
# we assume that the exterior boundary is that one with the biggest bounding box |
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if len(wires) > 0: |
if len(wires) > 0: |
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ext=None |
ext = None |
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max_length=0 |
max_length=0 |
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for i in wires: |
for i in wires: |
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if i.BoundBox.DiagonalLength > max_length: |
if i.BoundBox.DiagonalLength > max_length: |
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max_length = i.BoundBox.DiagonalLength |
max_length = i.BoundBox.DiagonalLength |
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ext = i |
ext = i |
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wires.remove(ext) |
wires.remove(ext) |
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# all interior wires mark a hole and must reverse their orientation, otherwise Part.Face fails |
# all interior wires mark a hole and must reverse their orientation, otherwise Part.Face fails |
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for i in wires: |
for i in wires: |
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i.reverse() |
i.reverse() |
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# make sure that the exterior wires comes as first in the |
# make sure that the exterior wires comes as first in the list |
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wires.insert(0, ext) |
wires.insert(0, ext) |
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faces.append(Part.Face(wires)) |
faces.append(Part.Face(wires)) |
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shell=Part.Compound(faces) |
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#Part.show(solid) |
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}} |
}} |
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{{docnav|Topological data scripting|Scenegraph}} |
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{{Powerdocnavi{{#translation:}}}} |
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[[Category:Python Code{{#translation:}}]] |
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{{Mesh Tools navi{{#translation:}}}} |
Latest revision as of 01:13, 22 August 2021
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)
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- FreeCAD scripting: Python, Introduction to Python, Python scripting tutorial, FreeCAD Scripting Basics
- Modules: Builtin modules, Units, Quantity
- Workbenches: Workbench creation, Gui Commands, Commands, Installing more workbenches
- Meshes and Parts: Mesh Scripting, Topological data scripting, Mesh to Part, PythonOCC
- Parametric objects: Scripted objects, Viewproviders (Custom icon in tree view)
- Scenegraph: Coin (Inventor) scenegraph, Pivy
- Graphical interface: Interface creation, Interface creation completely in Python (1, 2, 3, 4, 5), PySide, PySide examples beginner, intermediate, advanced
- Macros: Macros, How to install macros
- Embedding: Embedding FreeCAD, Embedding FreeCADGui
- Other: Expressions, Code snippets, Line drawing function, FreeCAD vector math library (deprecated)
- Hubs: User hub, Power users hub, Developer hub
- Miscellaneous: Import mesh, Export mesh, Create mesh from shape, Regular solid, Unwrap Mesh, Unwrap Face
- Modifying: Harmonize normals, Flip normals, Fill holes, Close hole, Add triangle, Remove components, Remove components by hand, Smooth, Refinement, Decimation, Scale
- Boolean: Union, Intersection, Difference
- Cutting: Cut mesh, Trim mesh, Trim mesh with a plane, Create section from mesh and plane, Cross-sections
- Components and segments: Merge, Split by components, Create mesh segments, Create mesh segments from best-fit surfaces