Mesh to Part/sv: Difference between revisions
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== Konvertera Del objekt till Nät == |
== Konvertera Del objekt till Nät == |
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Converting higher-level objects such as [[Part Module|Part shapes]] into simpler objects such as [[Mesh Module|meshes]] is a pretty simple operation, where all faces of a Part object get triangulated. The result of that triangulation (tessellation) is then used to construct a mesh: (let's assume our document contains one part object) |
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Att konvertera högnivåobjekt som [[Part Module/sv|Del former]] till enklare objekt som [[Mesh Module/sv|nät]] är en ganska enkel operation, där alla ytor på ett Del objekt blir triangulerade. Resultatet av denna triangulering (tessellering) används sedan till att konstruera ett nät: (Låt oss anta att vårt dokument innehåller ett Del objekt) |
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<syntaxhighlight> |
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</div> |
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#let's assume our document contains one part object |
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import Mesh |
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faces = [] |
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shape = FreeCAD.ActiveDocument.ActiveObject.Shape |
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triangles = shape.tessellate(1) # the number represents the precision of the tessellation) |
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for tri in triangles[1]: |
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face = [] |
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for i in range(3): |
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vindex = tri[i] |
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face.append(triangles[0][vindex]) |
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faces.append(face) |
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m = Mesh.Mesh(faces) |
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Mesh.show(m) |
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</syntaxhighlight> |
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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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<syntaxhighlight> |
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import Mesh |
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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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mesh=Mesh.Mesh() |
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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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{{Code|code= |
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</syntaxhighlight> |
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import Mesh |
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== Converting Meshes to Part objects == |
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obj = FreeCADGui.Selection.getSelection()[0] # a Part object must be preselected |
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Converting Meshes to Part objects is an extremely important operation in CAD work, because very often you receive 3D data in mesh format from other people or outputted from other applications. Meshes are very practical to represent free-form geometry and big visual scenes, as it is very lightweight, but for CAD we generally prefer higher-level objects that carry much more information, such as the idea of solid, or faces made of curves instead of triangles. |
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shp = obj.Shape |
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faces = [] |
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triangles = shp.tessellate(1) # the number represents the precision of the tessellation |
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Converting meshes to those higher-level objects (handled by the [[Part Module]] in FreeCAD) is not an easy operation. Meshes can be made of thousands of triangles (for example when generated by a 3D scanner), and having solids made of the same number of faces would be extremely heavy to manipulate. So you generally want to optimize the object when converting. |
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for tri in triangles[1]: |
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face = [] |
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for i in tri: |
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face.append(triangles[0][i]) |
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faces.append(face) |
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m = Mesh.Mesh(faces) |
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FreeCAD currently offers two methods to convert Meshes to Part objects. The first method is a simple, direct conversion, without any optimization: |
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Mesh.show(m) |
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<syntaxhighlight> |
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}} |
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import Mesh,Part |
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mesh = Mesh.createTorus() |
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shape = Part.Shape() |
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shape.makeShapeFromMesh(mesh.Topology,0.05) # the second arg is the tolerance for sewing |
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solid = Part.makeSolid(shape) |
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Part.show(solid) |
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Alternative example: |
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</syntaxhighlight> |
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The second method offers the possibility to consider mesh facets coplanar when the angle between them is under a certain value. This allows to build much simpler shapes: (let's assume our document contains one Mesh object) |
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<syntaxhighlight> |
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# let's assume our document contains one Mesh object |
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import Mesh,Part,MeshPart |
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faces = [] |
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mesh = App.ActiveDocument.ActiveObject.Mesh |
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segments = mesh.getPlanes(0.00001) # use rather strict tolerance here |
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for i in segments: |
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if len(i) > 0: |
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# a segment can have inner holes |
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wires = MeshPart.wireFromSegment(mesh, i) |
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# we assume that the exterior boundary is that one with the biggest bounding box |
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if len(wires) > 0: |
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ext=None |
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max_length=0 |
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for i in wires: |
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if i.BoundBox.DiagonalLength > max_length: |
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max_length = i.BoundBox.DiagonalLength |
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ext = i |
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wires.remove(ext) |
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# all interior wires mark a hole and must reverse their orientation, otherwise Part.Face fails |
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for i in wires: |
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i.reverse() |
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# make sure that the exterior wires comes as first in the lsit |
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wires.insert(0, ext) |
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faces.append(Part.Face(wires)) |
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shell=Part.Compound(faces) |
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Part.show(shell) |
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#solid = Part.Solid(Part.Shell(faces)) |
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#Part.show(solid) |
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{{Code|code= |
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</syntaxhighlight> |
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import Mesh |
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{{docnav|Topological data scripting|Scenegraph}} |
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import MeshPart |
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obj = FreeCADGui.Selection.getSelection()[0] # a Part object must be preselected |
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[[Category:Poweruser Documentation]] |
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shp = obj.Shape |
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[[Category:Python Code]] |
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mesh = FreeCAD.ActiveDocument.addObject("Mesh::Feature", "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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<div class="mw-translate-fuzzy"> |
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== Konvertera Nät till Del objekt == |
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</div> |
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Konvertering av Nät till Del objekt är en mycket viktig operation i CAD arbete, eftersom du mycket ofta tar emot 3D data i nätformat från andra människor eller utmatade från andra applikationer. Nät är mycket praktiskt för att representera friformsgeometri och stora visuella scener, eftersom den är mycket kompakt, men för CAD föredrar vi i allmänhet mer högnivåobjekt som bär mycket mer information, som solider, eller ytor som är skapade av kurvor istället för trianglar. |
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</div> |
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<div class="mw-translate-fuzzy"> |
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Konvertering av nät till dessa högnivåobjekt (hanterat av [[Part Module/sv|Del Modulen]] i FreeCAD) är inte en lätt operation. Nät kan vara gjord av tusentals trianglar (till exempel när de är genererade av en 3D skanner), och att ha solider gjorda med samma antal ytor skulle bli väldigt tungrott att manipulera. Så generellt sett så vill du optimera objektet när du konverterar. |
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</div> |
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<div class="mw-translate-fuzzy"> |
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FreeCAD erbjuder för närvarande två metoder för att konvertera Nät till Del objekt. Den första metoden är en enkel, direkt konvertering, utan någon optimering: |
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</div> |
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{{Code|code= |
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import Mesh |
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import Part |
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mesh = Mesh.createTorus() |
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shape = Part.Shape() |
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shape.makeShapeFromMesh(mesh.Topology, 0.05) # the second arg is the tolerance for sewing |
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solid = Part.makeSolid(shape) |
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Part.show(solid) |
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}} |
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<div class="mw-translate-fuzzy"> |
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Den andra metoden erbjuder möjligheten att anse nätfasetter koplanära när vinkeln mellan dem är under ett visst värde. Detta tillåter uppbyggnad av mycket enklare former: (Låt oss anta att vårt dokument innehåller ett Nät objekt) |
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</div> |
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{{Code|code= |
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import Mesh |
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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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mesh = obj.Mesh |
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segments = mesh.getPlanarSegments(0.00001) # use rather strict tolerance here |
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faces = [] |
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for i in segments: |
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if len(i) > 0: |
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# a segment can have inner holes |
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wires = MeshPart.wireFromSegment(mesh, i) |
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# we assume that the exterior boundary is that one with the biggest bounding box |
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if len(wires) > 0: |
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ext = None |
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max_length=0 |
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for i in wires: |
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if i.BoundBox.DiagonalLength > max_length: |
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max_length = i.BoundBox.DiagonalLength |
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ext = i |
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wires.remove(ext) |
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# all interior wires mark a hole and must reverse their orientation, otherwise Part.Face fails |
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for i in wires: |
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i.reverse() |
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# make sure that the exterior wires comes as first in the list |
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wires.insert(0, ext) |
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faces.append(Part.Face(wires)) |
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solid = Part.Solid(Part.Shell(faces)) |
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Part.show(solid) |
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}} |
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{{Powerdocnavi{{#translation:}}}} |
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[[Category:Developer Documentation{{#translation:}}]] |
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[[Category:Python Code{{#translation:}}]] |
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{{Mesh Tools navi{{#translation:}}}} |
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<languages/> |
Revision as of 21:13, 23 August 2020
Konvertera Del objekt till Nät
Att konvertera högnivåobjekt som Del former till enklare objekt som nät är en ganska enkel operation, där alla ytor på ett Del objekt blir triangulerade. Resultatet av denna triangulering (tessellering) används sedan till att konstruera ett nät: (Låt oss anta att vårt dokument innehåller ett Del objekt)
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)
Konvertera Nät till Del objekt
Konvertering av Nät till Del objekt är en mycket viktig operation i CAD arbete, eftersom du mycket ofta tar emot 3D data i nätformat från andra människor eller utmatade från andra applikationer. Nät är mycket praktiskt för att representera friformsgeometri och stora visuella scener, eftersom den är mycket kompakt, men för CAD föredrar vi i allmänhet mer högnivåobjekt som bär mycket mer information, som solider, eller ytor som är skapade av kurvor istället för trianglar.
Konvertering av nät till dessa högnivåobjekt (hanterat av Del Modulen i FreeCAD) är inte en lätt operation. Nät kan vara gjord av tusentals trianglar (till exempel när de är genererade av en 3D skanner), och att ha solider gjorda med samma antal ytor skulle bli väldigt tungrott att manipulera. Så generellt sett så vill du optimera objektet när du konverterar.
FreeCAD erbjuder för närvarande två metoder för att konvertera Nät till Del objekt. Den första metoden är en enkel, direkt konvertering, utan någon optimering:
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)
Den andra metoden erbjuder möjligheten att anse nätfasetter koplanära när vinkeln mellan dem är under ett visst värde. Detta tillåter uppbyggnad av mycket enklare former: (Låt oss anta att vårt dokument innehåller ett Nät objekt)
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)
- 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