Mesh to Part/es: Difference between revisions
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== |
== Converting Part objects to Meshes == |
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La conversión de objetos de alto nivel, tales como [[Part Module/es|formas de Piezas]] en objetos más simples como [[Mesh Module/es|mallas]] es una operación bastante sencilla, en la que todas las caras de un objeto Pieza son triangularizadas. El resultado de esa triangulación (o teselado) se utiliza para construir una malla: |
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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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<syntaxhighlight> |
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#let's assume our document contains one part object |
#let's assume our document contains one part object |
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import Mesh |
import Mesh |
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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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</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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En ocasiones, la triangulación ofrecida por ''OpenCascade'' para algunas caras es bastante fea. Si la cara tiene un espacio de parámetros rectangular y no contiene ningún agujero o curvas de corte también puedes crear una malla por tu cuenta: |
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<syntaxhighlight> |
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import Mesh |
import Mesh |
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def makeMeshFromFace(u,v,face): |
def makeMeshFromFace(u,v,face): |
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return mesh |
return mesh |
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</syntaxhighlight> |
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== Convertir Mallas en objetos Pieza == |
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== Converting Meshes to Part objects == |
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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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La conversión de mallas en objetos Pieza es una operación muy importante en el trabajo de CAD, ya que a menudo se reciben datos 3D en formato de malla de otras personas o son generados con otras aplicaciones. Las mallas son muy prácticas para representar la geometría de forma libre y para grandes escenas visuales, ya que son muy ligeras. Pero, por lo general, el CAD prefiere objetos de nivel superior que llevan mucha más información, como la idea de sólidos, o caras hechas de curvas, en lugar de triángulos. |
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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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La conversión de las mallas a esos objetos de nivel superior (manejados por el [[Part Module/es|Módulo de Piezas]] en FreeCAD) no es una operación fácil. Las mallas pueden tener miles de triángulos (por ejemplo, los generados por un escáner 3D), y si los sólidos se hacen con el mismo número de caras, serían extremadamente pesados de manipular. Así que por lo general, se desea optimizar el objeto durante la conversión. |
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FreeCAD actualmente ofrece dos métodos para convertir mallas en piezas. El primer método es una conversión sencilla, directa, sin ningún tipo de optimización: |
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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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<syntaxhighlight> |
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import Mesh,Part |
import Mesh,Part |
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mesh = Mesh.createTorus() |
mesh = Mesh.createTorus() |
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Part.show(solid) |
Part.show(solid) |
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</syntaxhighlight> |
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El segundo método ofrece la posibilidad de considerar coplanares las facetas de malla que forman entre si un pequeño ángulo. Esto permite la construcción de formas mucho más simples: |
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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 |
# let's assume our document contains one Mesh object |
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import Mesh,Part,MeshPart |
import Mesh,Part,MeshPart |
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#Part.show(solid) |
#Part.show(solid) |
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</syntaxhighlight> |
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{{clear}} |
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<languages/> |
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{{languages/es | {{en|Mesh to Part}} {{fr|Mesh to Part/fr}} {{it|Mesh to Part/it}} {{ru|Mesh to Part/ru}} {{se|Mesh to Part/se}} }} |
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⚫ | |||
⚫ |
Revision as of 20:42, 30 September 2014
Converting Part objects to Meshes
Converting higher-level objects such as Part shapes into simpler objects such as 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)
#let's assume our document contains one part object
import Mesh
faces = []
shape = FreeCAD.ActiveDocument.ActiveObject.Shape
triangles = shape.tessellate(1) # the number represents the precision of the tessellation)
for tri in triangles[1]:
face = []
for i in range(3):
vindex = tri[i]
face.append(triangles[0][vindex])
faces.append(face)
m = Mesh.Mesh(faces)
Mesh.show(m)
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:
import Mesh
def makeMeshFromFace(u,v,face):
(a,b,c,d)=face.ParameterRange
pts=[]
for j in range(v):
for i in range(u):
s=1.0/(u-1)*(i*b+(u-1-i)*a)
t=1.0/(v-1)*(j*d+(v-1-j)*c)
pts.append(face.valueAt(s,t))
mesh=Mesh.Mesh()
for j in range(v-1):
for i in range(u-1):
mesh.addFacet(pts[u*j+i],pts[u*j+i+1],pts[u*(j+1)+i])
mesh.addFacet(pts[u*(j+1)+i],pts[u*j+i+1],pts[u*(j+1)+i+1])
return mesh
Converting Meshes to Part objects
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.
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.
FreeCAD currently offers two methods to convert Meshes to Part objects. The first method is a simple, direct conversion, without any optimization:
import Mesh,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 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)
# let's assume our document contains one Mesh object
import Mesh,Part,MeshPart
faces = []
mesh = App.ActiveDocument.ActiveObject.Mesh
segments = mesh.getPlanes(0.00001) # use rather strict tolerance here
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 lsit
wires.insert(0, ext)
faces.append(Part.Face(wires))
shell=Part.Compound(faces)
Part.show(shell)
#solid = Part.Solid(Part.Shell(faces))
#Part.show(solid)