PythonOCC omogoča enostavnejšo uporabo jedra modelirnika OpenCascade v jeziku Python. Prednost Pythona v primerjavi z C++ je:

• Prenosljivosti. Programi se interpretirajo in jih ni potrebno prevajati zato delujejo na vseh operacijskih sistemih. So pa nekoliko počasnejši.
• Enostavnejša namestitev potrebnih knjižnic, brez zahtevne konfiguracije povezovalnih parametrov, ki so značilni za C++.
• Lažje učenje jezika. V interaktivnem načinu obstaja tudi refleksija oziroma dinamično prepoznavanje možnih ukazov v objektu.

Za vaje, si je potrebno na osebnem računalniku z 64-bitnimi Windows-i pripraviti okolje po naslednjih korakih:

1. ​Anaconda upravljalnik paketov.
2. V terminalu napišite ukaz: conda install -c https://conda.anaconda.org/dlr-sc pythonocc-core=0.17
3. ​PyCharm urejevalnik.
4. Ustvarite datoteko core-hello.py z naslednjo vsebino in preverite ali vam prikaže kocko v 3D.

   from OCC.Display.SimpleGui import init_display
   from OCC.BRepPrimAPI import BRepPrimAPI_MakeBox
   
   display, start_display, add_menu, add_function_to_menu = init_display()
   my_box = BRepPrimAPI_MakeBox(10., 20., 30.).Shape()
   
   display.DisplayShape(my_box, update=True)
   start_display()
   

Predstavitev CAD-jedra Open CASCADE na primerih

Osnove gradnje modelov so podane na strani PythonOcc/primitives in PythonOcc/elbow

Uvod v modeliranje PythonOCC s 3D primitivi

V tem primeru je namen pokazati enostavne aplikacije:

• izdelava menuja in dva podmenuja
• ta dva menuja izdelata: i. kocko in ii. cilinder

Najprej kličemo knjižnico za enostaven uporabniški vmesnik SimpleGUI:

# -*- coding: utf-8 -*- 
from OCC.Display.SimpleGui import *

V naslednjem koraku inicializiramo funkcije za display:

display, start_display, add_menu, add_function_to_menu = init_display()

Nato definiramo dve funkciji, ki izdelata kocko in cilinder:

def kocka(event=None):
    from OCC.BRepPrimAPI import BRepPrimAPI_MakeBox
    display.EraseAll()
    my_box= BRepPrimAPI_MakeBox(10., 20., 30.)
    display.DisplayShape(my_box.Shape())

def valj(event=None):
    from OCC.BRepPrimAPI import BRepPrimAPI_MakeCylinder
    display.EraseAll()
    my_cylinder = BRepPrimAPI_MakeCylinder(60, 200)
    display.DisplayShape(my_cylinder.Shape())

Izdelava menija 'simple test' in dodajanje funkcij v podmenije:

add_menu('enostaven primer')
add_function_to_menu('enostaven primer', kocka)
add_function_to_menu('enostaven primer', valj)

Na koncu renderiramo 3D model:

display.View_Iso()
display.FitAll()

start_display() # Zanka start_display() je neskončna

Namesto uporabe klasičnih primitivov, lahko kocko zgradimo tudi z izvlekom žičnega modela.

# -*- coding: utf-8 -*-
## Izdelava kocke

from OCC.Display.SimpleGui import *
from OCC.BRepPrimAPI import *
from OCC.gp import *
from OCC.GC import *
from OCC.BRepBuilderAPI import *
#from OCC.TopoDS import *

display, start_display, add_menu, add_function_to_menu = init_display()

#Definiranje točk v prostoru
aPnt1 = gp_Pnt(0 , 0 , 0)
aPnt2 = gp_Pnt(10 , 0, 0)
aPnt3 = gp_Pnt(10 , 10 , 0)
aPnt4 = gp_Pnt(0, 10 , 0)

#Izdelava segmentov--definiranje geometrije
aSegment1 = GC_MakeSegment(aPnt1 , aPnt2)
aSegment2 = GC_MakeSegment(aPnt2 , aPnt3)
aSegment3 = GC_MakeSegment(aPnt3 , aPnt4)
aSegment4 = GC_MakeSegment(aPnt4 , aPnt1)

#Izdelava robov -- definiranje topologije
aEdge1 = BRepBuilderAPI_MakeEdge(aSegment1.Value())
aEdge2 = BRepBuilderAPI_MakeEdge(aSegment2.Value())
aEdge3 = BRepBuilderAPI_MakeEdge(aSegment3.Value())
aEdge4 = BRepBuilderAPI_MakeEdge(aSegment4.Value())

'''
#Robove se lahko določi tudi direktno s točkami:
aEdge1 = BRepBuilderAPI_MakeEdge(aPnt1, aPnt2)
aEdge2 = BRepBuilderAPI_MakeEdge(aPnt2, aPnt3)
aEdge3 = BRepBuilderAPI_MakeEdge(aPnt3, aPnt4)
aEdge4 = BRepBuilderAPI_MakeEdge(aPnt4, aPnt1)
'''
#Povezovanje robov v mrežo
aWire  = BRepBuilderAPI_MakeWire(aEdge1.Edge() , aEdge2.Edge() ,\
                                 aEdge3.Edge(), aEdge4.Edge())

#Telo: Iz profila se izdela telo
myFaceProfile = BRepBuilderAPI_MakeFace(aWire.Wire())

aPrismVec = gp_Vec(0 , 0 , 10)

myBody = BRepPrimAPI_MakePrism(myFaceProfile.Face() , aPrismVec).Shape()

#Spodaj so zakomentirani ukazi za prikazovanje posameznih delov.
'''
#Prikaz točk
display.DisplayShape(aPnt1)
display.DisplayShape(aPnt2)
display.DisplayShape(aPnt3)
display.DisplayShape(aPnt4)
'''
'''
#Prikaz robov
display.DisplayShape(aEdge1.Shape())
display.DisplayShape(aEdge2.Shape())
display.DisplayShape(aEdge3.Shape())
display.DisplayShape(aEdge4.Shape())
'''
'''
#Prikaz mreže
display.DisplayShape(aWire.Shape())
'''
'''
#Prikaz profila
display.DisplayShape(myFaceProfile.Shape())
'''
#Prikaz telesa
display.DisplayShape(myBody)

start_display()

Slikovni pregled izdelave 3D modela

1. Definiranje točk v prostoru:

    aPnt1 = gp_Pnt(x_1 , y_1 , z_1) --> aPnt4 = gp_Pnt(x_4 , y_4 , z_4)
   

2. Iz točk v prostoru se tvori robove (en rob je sestavljen iz najmanj dveh točk):

   myEdge1 = BRepBuilderAPI_MakeEdge(aPnt1, aPnt2) --> myEdge4 = BRepBuilderAPI_MakeEdge(aPnt4, aPnt1)
   

3. Ko imamo vse robove izdelamo mrežo:

   myWire  = BRepBuilderAPI_MakeWire(aEdge1.Edge() , aEdge2.Edge() ,aEdge3.Edge(), aEdge4.Edge())
   

4. Iz mreže tvorimo površino (mreža mora biti zaprta):

   myFace = BRepBuilderAPI_MakeFace(myWire)
   

5. Definiranje prostorskega vektorja, ki bo določal smer izvleka (ekstrudiranja) površine:

   myVec = gp_Vec(n_x , n_y , n_z)
   

6. Z površino in smernim vektorjem izdelamo 3D model:

   myBody = BRepPrimAPI_MakePrism(myFace.Face() , myVec)
   

Pregled uporabljenih OCC knjižnic

## Importanje različnih knjižnic

# Uporabniški vmesnik GUI
from OCC.Display.SimpleGui import *

# Matematična knjižnica
import math

# OpenCascade
from OCC.gp import * #točke
from OCC.BRepBuilderAPI import * #gradimo robove, segmente, mreže ...
from OCC.BRepPrimAPI import * #izdelava osnovnih geometrijskih primitivov
from OCC.BRepFilletAPI import * #izdelava zaokrožitev

Točnejša navodila, opis funkcij in knjižnic lahko dobimo v PythonOCC dokumentaciji.

Inicializacija zaslona in izdelava grafičnega vmesnika

# OCC.Display.SimpleGui.init_display() returns multiple
# values which are assigned here
display, start_display, add_menu, add_function_to_menu = \
init_display()
draw_bottle() #kličemo CAD model, ki ga želimo prikazati na zaslonu
start_display()

Risanje točk v prostoru

Izdelava točk v prostoru je najosnovnejša operacija v OCC.

# Definiranje začetnih točk
aPnt1 = gp_Pnt(-myWidth / 2. , 0 , 0)
aPnt2 = gp_Pnt(-myWidth / 2. , -myThickness / 4. , 0)
aPnt3 = gp_Pnt(0 , -myThickness / 2. , 0)
aPnt4 = gp_Pnt(myWidth / 2. , -myThickness / 4. , 0)
aPnt5 = gp_Pnt(myWidth / 2. , 0 , 0)

Izdelava robnih elementov

V naslednjem koraku se iz začetnih točk izdela robove:

# Definiranje geometrije
aArcOfCircle = GC_MakeArcOfCircle(aPnt2,aPnt3 ,aPnt4)
aSegment1 = GC_MakeSegment(aPnt1 , aPnt2)
aSegment2 = GC_MakeSegment(aPnt4 , aPnt5)

# Definiranje topologije
aEdge1 = BRepBuilderAPI_MakeEdge(aSegment1.Value())
aEdge2 = BRepBuilderAPI_MakeEdge(aArcOfCircle.Value())
aEdge3 = BRepBuilderAPI_MakeEdge(aSegment2.Value())

Povezovanje robnih elementov v mreže

Robne elemente se v nadaljevanju združi v mrežo.

# Izdelava mreže
aWire  = BRepBuilderAPI_MakeWire(aEdge1.Edge() , aEdge2.Edge() ,aEdge3.Edge())

Uporaba funkcij za izdelavo objektov v prostoru

# Izdelava celotnega profila - mirror
xAxis = gp_OX()
aTrsf = gp_Trsf()
aTrsf.SetMirror(xAxis)
aBRepTrsf = BRepBuilderAPI_Transform(aWire.Shape() , aTrsf)
aMirroredShape = aBRepTrsf.Shape()
aMirroredWire = topods_Wire(aMirroredShape)
mkWire = BRepBuilderAPI_MakeWire()
mkWire.Add(aWire.Wire())
mkWire.Add(aMirroredWire)
myWireProfile = mkWire.Wire()

# Telo: Iz profila se izdela telo (Funkcija izvleka 3D)
myFaceProfile = BRepBuilderAPI_MakeFace(myWireProfile)
aPrismVec = gp_Vec(0 , 0 , myHeight)
myBody = BRepPrimAPI_MakePrism(myFaceProfile.Face() , aPrismVec)

Risanje geometrijskih primitivov

V OCC že obstajajo funkcije za izdelavo geometrijskih primitivov (kocka, valj,...), kar je prikazano na spodnjem primeru.

from OCC.Display.SimpleGui import *
from OCC.BRepPrimAPI import *

display, start_display, add_menu, add_function_to_menu = init_display()
my_box = BRepPrimAPI_MakeBox(10.,20.,30.).Shape()
# ali my_cylinder = BRepPrimAPI_MakeCylinder(neckAx2 , myNeckRadius , myNeckHeight), kjer so spremenljivke že preddefinirane 

display.DisplayShape(my_box) # ali display.DisplayShape(my_cylinder)
start_display()

Risanje različnih tipov robov

##Copyright 2009-2015 Thomas Paviot (tpaviot@gmail.com)
##
##This file is part of pythonOCC.
##
##pythonOCC is free software: you can redistribute it and/or modify
##it under the terms of the GNU Lesser General Public License as published by
##the Free Software Foundation, either version 3 of the License, or
##(at your option) any later version.
##
##pythonOCC is distributed in the hope that it will be useful,
##but WITHOUT ANY WARRANTY; without even the implied warranty of
##MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
##GNU Lesser General Public License for more details.
##
##You should have received a copy of the GNU Lesser General Public License
##along with pythonOCC.  If not, see <http://www.gnu.org/licenses/>.

import math

from OCC.gp import gp_Pnt, gp_Lin, gp_Ax1, gp_Dir, gp_Elips, gp_Ax2
from OCC.BRepBuilderAPI import (BRepBuilderAPI_MakeEdge,
                                BRepBuilderAPI_MakeVertex)
from OCC.TColgp import TColgp_Array1OfPnt
from OCC.Geom import Geom_BezierCurve

from OCC.Display.SimpleGui import init_display
display, start_display, add_menu, add_function_to_menu = init_display()


def edge(event=None):
    # The blue edge
    BlueEdge = BRepBuilderAPI_MakeEdge(gp_Pnt(-80, -50, -20),
                                       gp_Pnt(-30, -60, -60))
    V1 = BRepBuilderAPI_MakeVertex(gp_Pnt(-20, 10, -30))
    V2 = BRepBuilderAPI_MakeVertex(gp_Pnt(10, 7, -25))
    YellowEdge = BRepBuilderAPI_MakeEdge(V1.Vertex(), V2.Vertex())

    #The white edge
    line = gp_Lin(gp_Ax1(gp_Pnt(10, 10, 10), gp_Dir(1, 0, 0)))
    WhiteEdge = BRepBuilderAPI_MakeEdge(line, -20, 10)

    #The red edge
    Elips = gp_Elips(gp_Ax2(gp_Pnt(10, 0, 0), gp_Dir(1, 1, 1)), 60, 30)
    RedEdge = BRepBuilderAPI_MakeEdge(Elips, 0, math.pi/2)

    # The green edge and the both extreme vertex
    P1 = gp_Pnt(-15, 200, 10)
    P2 = gp_Pnt(5, 204, 0)
    P3 = gp_Pnt(15, 200, 0)
    P4 = gp_Pnt(-15, 20, 15)
    P5 = gp_Pnt(-5, 20, 0)
    P6 = gp_Pnt(15, 20, 0)
    P7 = gp_Pnt(24, 120, 0)
    P8 = gp_Pnt(-24, 120, 12.5)
    array = TColgp_Array1OfPnt(1, 8)
    array.SetValue(1, P1)
    array.SetValue(2, P2)
    array.SetValue(3, P3)
    array.SetValue(4, P4)
    array.SetValue(5, P5)
    array.SetValue(6, P6)
    array.SetValue(7, P7)
    array.SetValue(8, P8)
    curve = Geom_BezierCurve(array)
    ME = BRepBuilderAPI_MakeEdge(curve.GetHandle())
    GreenEdge = ME
    V3 = ME.Vertex1()
    V4 = ME.Vertex2()

    display.DisplayColoredShape(BlueEdge.Edge(), 'BLUE')
    display.DisplayShape(V1.Vertex())
    display.DisplayShape(V2.Vertex())
    display.DisplayColoredShape(WhiteEdge.Edge(), 'WHITE')
    display.DisplayColoredShape(YellowEdge.Edge(), 'YELLOW')
    display.DisplayColoredShape(RedEdge.Edge(), 'RED')
    display.DisplayColoredShape(GreenEdge.Edge(), 'GREEN')
    display.DisplayShape(V3)
    display.DisplayShape(V4, update=True)

if __name__ == '__main__':
    edge()
    start_display()

Risanje prerezane piramide

##Copyright 2009-2015 Thomas Paviot (tpaviot@gmail.com)
##
##This file is part of pythonOCC.
##
##pythonOCC is free software: you can redistribute it and/or modify
##it under the terms of the GNU Lesser General Public License as published by
##the Free Software Foundation, either version 3 of the License, or
##(at your option) any later version.
##
##pythonOCC is distributed in the hope that it will be useful,
##but WITHOUT ANY WARRANTY; without even the implied warranty of
##MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
##GNU Lesser General Public License for more details.
##
##You should have received a copy of the GNU Lesser General Public License
##along with pythonOCC.  If not, see <http://www.gnu.org/licenses/>.

import math
from OCC.gp import gp_Dir, gp_Pln, gp_Ax3, gp_XOY
from OCC.BRepPrimAPI import BRepPrimAPI_MakeBox
from OCC.BRepOffsetAPI import BRepOffsetAPI_DraftAngle
from OCC.Precision import precision_Angular
from OCC.BRep import BRep_Tool_Surface
from OCC.TopExp import TopExp_Explorer
from OCC.TopAbs import TopAbs_FACE
from OCC.Geom import Handle_Geom_Plane_DownCast
from OCC.TopoDS import topods_Face

from OCC.Display.SimpleGui import init_display
display, start_display, add_menu, add_function_to_menu = init_display()


def draft_angle(event=None):
    S = BRepPrimAPI_MakeBox(200., 300., 150.).Shape()
    adraft = BRepOffsetAPI_DraftAngle(S)
    topExp = TopExp_Explorer()
    topExp.Init(S, TopAbs_FACE)
    while topExp.More():
        face = topods_Face(topExp.Current())
        surf = Handle_Geom_Plane_DownCast(BRep_Tool_Surface(face)).GetObject()
        dirf = surf.Pln().Axis().Direction()
        ddd = gp_Dir(0, 0, 1)
        if dirf.IsNormal(ddd, precision_Angular()):
            adraft.Add(face, ddd, math.radians(15), gp_Pln(gp_Ax3(gp_XOY())))
        topExp.Next()
    adraft.Build()
    display.DisplayShape(adraft.Shape(), update=True)


if __name__ == '__main__':
    draft_angle()
    start_display()

Izdelava primera Bottle z uporabo programskega jezika Python in knjižnice OCC

Naslednji primer prikazuje izdelavo primera BottleCAD. Podrobnejši razdelek posameznih delov programske kode dobimo na ​MakeBottleCAD(C++).

##Copyright 2011 Simon Kulovec (simon.kulovec@lecad.si) 
##Uredil in posodobil 2015 Dejan Penko (dejan.penko@lecad.fs.uni-lj.si)
##Example: MakeCADBottle
##This file is part of pythonOCC.

## Importanje različnih knjižnic

# Uporabniški vmesnik GUI
from OCC.Display.SimpleGui import *

# OpenCascade
from OCC.gp import *
from OCC.TopoDS import *
from OCC.GC import *
from OCC.BRepBuilderAPI import *
from OCC.BRepPrimAPI import *
from OCC.BRepFilletAPI import *
from OCC.BRepAlgoAPI import *
from OCC.Geom import *
from OCC.Geom2d import *
from OCC.GCE2d import *
from OCC.BRep import *
from OCC.BRepLib import *
from OCC.BRepOffsetAPI import *
from OCC.TopTools import *
from OCC.TopAbs import *
from OCC.TopExp import *

import math

#Naslednja podprograma "face_is_plane" in "geom_plane_from_face" sta napisana za pomoč v nadaljevanju programa
def face_is_plane(face):
    """
    Vrne True če je TopoDS_Shape ravnina, False v nasprotnem primeru
    """
    hs = BRep_Tool_Surface(face)
    downcast_result = Handle_Geom_Plane.DownCast(hs)
    # Vrednost je "null", če se izvedba tega podprograma ne izvede pravilo ali je ni mogoče izvesti. Iz tega sledi, da profil ni ravnina
    if downcast_result.IsNull():
        return False
    else:
        return True

def geom_plane_from_face(aFace):
    """
    Vrne subjekt geometrične ravnine iz ravninske površine
    """
    return Handle_Geom_Plane.DownCast(BRep_Tool_Surface(aFace)).GetObject()

def show_bottle(aRes):
    display.EraseAll()
    #print (dir(display))
    display.DisplayShape(aRes)

def define_body(myWidth, myThickness, myHeight):
    ## Definiranje začetnih točk
    aPnt1 = gp_Pnt(-myWidth / 2. , 0 , 0)
    aPnt2 = gp_Pnt(-myWidth / 2. , -myThickness / 4. , 0)
    aPnt3 = gp_Pnt(0 , -myThickness / 2. , 0)
    aPnt4 = gp_Pnt(myWidth / 2. , -myThickness / 4. , 0)
    aPnt5 = gp_Pnt(myWidth / 2. , 0 , 0)

    ## Definiranje geometrije
    aArcOfCircle = GC_MakeArcOfCircle(aPnt2,aPnt3 ,aPnt4)
    aSegment1 = GC_MakeSegment(aPnt1 , aPnt2)
    aSegment2 = GC_MakeSegment(aPnt4 , aPnt5)

    ## Definiranje topologije
    #Definiranje robov
    aEdge1 = BRepBuilderAPI_MakeEdge(aSegment1.Value())
    aEdge2 = BRepBuilderAPI_MakeEdge(aArcOfCircle.Value())
    aEdge3 = BRepBuilderAPI_MakeEdge(aSegment2.Value())
    #Definiranje robov iz mreže
    aWire  = BRepBuilderAPI_MakeWire(aEdge1.Edge() , aEdge2.Edge() ,aEdge3.Edge())

    ## Izdelava celotnega profila - mirror
    #Definiramo os zrcaljenja (os X)
    xAxis = gp_OX()
    #Nastavimo "zrcalo"
    aTrsf = gp_Trsf()
    aTrsf.SetMirror(xAxis)
    #Uporabimo zrcalno transformacijo
    aBRepTrsf = BRepBuilderAPI_Transform(aWire.Shape() , aTrsf)
    #Zrcalno obliko dobimo nazaj iz transformacije in pretvorimo v mrežo
    aMirroredShape = aBRepTrsf.Shape()
    aMirroredWire = topods_Wire(aMirroredShape) 
    #Kombiniramo dve konsistentni mreži
    mkWire = BRepBuilderAPI_MakeWire()
    mkWire.Add(aWire.Wire())
    mkWire.Add(aMirroredWire)
    myWireProfile = mkWire.Wire()

    ## Telo:
    #Iz profila se izdela telo
    myFaceProfile = BRepBuilderAPI_MakeFace(myWireProfile)
    aPrismVec = gp_Vec(0 , 0 , myHeight)
    myBody = BRepPrimAPI_MakePrism(myFaceProfile.Face() , aPrismVec)

    #Dodamo zaokrožitve (fillet) s pomočjo t. i. Explorerja
    mkFillet = BRepFilletAPI_MakeFillet(myBody.Shape())

    anEdgeExplorer = TopExp_Explorer(myBody.Shape(), TopAbs_EDGE)

    while anEdgeExplorer.More():
        anEdge = topods.Edge(anEdgeExplorer.Current())
        mkFillet.Add(myThickness / 12.0, anEdge)

        anEdgeExplorer.Next()

    myBody = mkFillet

    ##Dodajanje grla na steklenico
    neckLocation = gp_Pnt(0, 0, myHeight)
    neckNormal = gp_DZ()
    neckAx2 = gp_Ax2(neckLocation, neckNormal)

    myNeckRadius = myThickness / 4
    myNeckHeight = myHeight / 10

    mkCylinder = BRepPrimAPI_MakeCylinder(neckAx2 , myNeckRadius , myNeckHeight)
                                          
    myNeck = mkCylinder;

    myBody = BRepAlgoAPI_Fuse(myBody.Shape(), myNeck.Shape())

    ## Izdelava votle steklenice
    #CILJ: Poiščemo najvišji Z profil in ga odstranimo
    faceToRemove = None
    zMax = -1;

    #Če želimo najti najvišji Z profil, katerega želimo odstraniti iz lupine, je potrebno iti skozi vse profile
    aFaceExplorer = TopExp_Explorer(myBody.Shape(), TopAbs_FACE)
    while aFaceExplorer.More():
        aFace = topods.Face(aFaceExplorer.Current())

        if face_is_plane(aFace):
            aPlane = geom_plane_from_face(aFace)

            # We want the highest Z face, so compare this to the previous faces
            aPnt = aPlane.Location()
            aZ = aPnt.Z()
            if aZ > zMax:
                zMax = aZ
                faceToRemove = aFace

        aFaceExplorer.Next()
    
    facesToRemove = TopTools_ListOfShape()
    facesToRemove.Append(faceToRemove)
    myBody = BRepOffsetAPI_MakeThickSolid(myBody.Shape() , facesToRemove , \
                                          -myThickness/50 , 1.e-3)
    
    ## Navoj na vratu steklenice:
    #Ustvarjanje površine
    aCyl1 = Geom_CylindricalSurface(gp_Ax3(neckAx2) , myNeckRadius * 0.99)
    aCyl2 = Geom_CylindricalSurface(gp_Ax3(neckAx2) , myNeckRadius * 1.05)

    #Definiranje 2D krivulje navoja 
    aPnt = gp_Pnt2d(2. * math.pi , myNeckHeight / 2.)
    aDir = gp_Dir2d(2. * math.pi , myNeckHeight / 4.)
    aAx2d = gp_Ax2d(aPnt , aDir)
        
    aMajor = 2.0 * math.pi
    aMinor = myNeckHeight / 10.
    
    anEllipse1 = Geom2d_Ellipse(aAx2d , aMajor , aMinor)
    anEllipse2 = Geom2d_Ellipse(aAx2d , aMajor , aMinor / 4.0)

    anArc1 = Geom2d_TrimmedCurve(Handle_Geom2d_Ellipse(anEllipse1), 0, math.pi)
    anArc2 = Geom2d_TrimmedCurve(Handle_Geom2d_Ellipse(anEllipse2), 0, math.pi)
    
    anEllipsePnt2 = anEllipse1.Value(0.)
    anEllipsePnt1 = anEllipse1.Value(math.pi)
    
    aSegment = GCE2d_MakeSegment(anEllipsePnt1 , anEllipsePnt2)

    #Robovi in mreže
    aEdge1OnSurf1 = BRepBuilderAPI_MakeEdge(anArc1.GetHandle() , aCyl1.GetHandle())
    aEdge2OnSurf1 = BRepBuilderAPI_MakeEdge(aSegment.Value() , aCyl1.GetHandle())
    aEdge1OnSurf2 = BRepBuilderAPI_MakeEdge(anArc2.GetHandle() , aCyl2.GetHandle())
    aEdge2OnSurf2 = BRepBuilderAPI_MakeEdge(aSegment.Value() , aCyl2.GetHandle())
    #print (dir(aEdge1OnSurf1))
    threadingWire1 = BRepBuilderAPI_MakeWire(aEdge1OnSurf1.Edge() , aEdge2OnSurf1.Edge())
    threadingWire2 = BRepBuilderAPI_MakeWire(aEdge1OnSurf2.Edge() , aEdge2OnSurf2.Edge())

    #3D predstava robov/mrež
    breplib.BuildCurves3d(threadingWire1.Shape())
    breplib.BuildCurves3d(threadingWire2.Shape())
    
    #Površina navoja
    aTool = BRepOffsetAPI_ThruSections(True)
    aTool.AddWire(threadingWire1.Wire())
    aTool.AddWire(threadingWire2.Wire())
    aTool.CheckCompatibility(False)
    myThreading = aTool.Shape()

    ## Izdelava sestava
    aRes = TopoDS_Compound()

    aBuilder = BRep_Builder()
    aBuilder.MakeCompound (aRes)

    aBuilder.Add (aRes, myBody.Shape())
    aBuilder.Add (aRes, myThreading)

    ## Izris oblike
    show_bottle(aRes)

def draw_bottle(event=None):
    # Definiranje razdalj: širina, dolžina, višina
    myWidth = 50.0
    myThickness = 30.0
    myHeight = 70.0
    # Define Points
    define_body(myWidth, myThickness, myHeight)
    
if __name__ == '__main__':
    # OCC.Display.SimpleGui.init_display() returns multiple
    # values which are assigned here
    display, start_display, add_menu, add_function_to_menu = \
    init_display()
    draw_bottle() #kličemo podprogram za izris bottle
    start_display()

Izris CAD prizme

## Izdelava prizme --primer bottle

from OCC.Display.SimpleGui import *
from OCC.BRepPrimAPI import *
from OCC.gp import *
from OCC.GC import *
from OCC.BRepBuilderAPI import *
from OCC.TopoDS import *

display, start_display, add_menu, add_function_to_menu = init_display()

myWidth = 50.0
myThickness = 30.0
myHeight = 70.0

#Definiranje začetnih točk
aPnt1 = gp_Pnt(-myWidth / 2. , 0 , 0)
aPnt2 = gp_Pnt(-myWidth / 2. , -myThickness / 4. , 0)
aPnt3 = gp_Pnt(0 , -myThickness / 2. , 0)
aPnt4 = gp_Pnt(myWidth / 2. , -myThickness / 4. , 0)
aPnt5 = gp_Pnt(myWidth / 2. , 0 , 0)

#Izdelava segmentov--definiranje geometrije
aArcOfCircle = GC_MakeArcOfCircle(aPnt2,aPnt3 ,aPnt4)
aSegment1 = GC_MakeSegment(aPnt1 , aPnt2)
aSegment2 = GC_MakeSegment(aPnt4 , aPnt5)

#Izdelava robov -- definiranje topologije
aEdge1 = BRepBuilderAPI_MakeEdge(aSegment1.Value())
aEdge2 = BRepBuilderAPI_MakeEdge(aArcOfCircle.Value())
aEdge3 = BRepBuilderAPI_MakeEdge(aSegment2.Value())

#Povezovanje robov v mrežo
aWire  = BRepBuilderAPI_MakeWire(aEdge1.Edge() , aEdge2.Edge() ,\
                                 aEdge3.Edge())

#Izdelava celotnega profila - mirror
xAxis = gp_OX()
aTrsf = gp_Trsf()
aTrsf.SetMirror(xAxis)
aBRepTrsf = BRepBuilderAPI_Transform(aWire.Shape() , aTrsf)
aMirroredShape = aBRepTrsf.Shape()
aMirroredWire = topods.Wire(aMirroredShape)
mkWire = BRepBuilderAPI_MakeWire()
mkWire.Add(aWire.Wire())
mkWire.Add(aMirroredWire)
myWireProfile = mkWire.Wire()

#Telo: Iz profila se izdela telo
myFaceProfile = BRepBuilderAPI_MakeFace(myWireProfile)
aPrismVec = gp_Vec(0 , 0 , myHeight)
myBody = BRepPrimAPI_MakePrism(myFaceProfile.Face() , aPrismVec).Shape()

display.DisplayShape(myBody)
start_display()

Povzetek prve vaje

Prikaz enostavnega izvoza STEP formata za eno obliko

# Vključimo knjižnico za izvoz STEP formata
from OCC.STEPControl import *

from OCC.BRepPrimAPI import *

# Pripravimo enostaven CAD primer za izvoz v STEP format
my_box_shape = BRepPrimAPI_MakeBox(50,50,50).Shape() # Izdelava kocke

# Obliko my_box_shape izvozimo v STEP format
step_writer = STEPControl_Writer()
step_writer.Transfer(my_box_shape, STEPControl_AsIs)
step_writer.Write("result_export_single.stp")

Prikaz enostavnega izvoza STEP formata za več oblik

# Vključimo knjižnico za izvoz STEP formata
from OCC.STEPControl import *

from OCC.BRepPrimAPI import *

# Pripravimo enostavna CAD primera za izvoz v STEP format
my_box_shape = BRepPrimAPI_MakeBox(50,50,50).Shape() # Izdelava kocke
my_sphere_shape = BRepPrimAPI_MakeSphere(20).Shape() # Izdelava krogle

# Obliki my_box_shape in my_sphere_shape izvozimo v STEP format
step_writer = STEPControl_Writer()
step_writer.Transfer(my_box_shape, STEPControl_AsIs)
step_writer.Transfer(my_sphere_shape, STEPControl_AsIs)
step_writer.Write("result_export_multi.stp")

Prikaz izvoza CAD modelov z barvami in layer.ji

# Vključimo knjižnico za izvoz STEP formata
from OCC.Utils.DataExchange.STEP import StepOCAF_Export

from OCC.BRepPrimAPI import *

# Pripravimo enostavna CAD primera za izvoz v STEP format
my_box_shape = BRepPrimAPI_MakeBox(50,50,50).Shape() # Izdelava kocke
my_sphere_shape = BRepPrimAPI_MakeSphere(20).Shape() # Izdelava krogle

# Export to STEP
my_step_exporter = StepOCAF_Export("result_export_multi_color_layer.stp") # Določitev imena file.a
my_step_exporter.set_color(1,0,0) # določitev barve (rdeča) -> RedGreenBlue paleta barv (RGB)
my_step_exporter.set_layer('red') # določitev layer.ja
my_step_exporter.add_shape(my_box_shape) # izbira oblike za izbrane parametre my_box_shape
my_step_exporter.set_color(0,1,0) 
my_step_exporter.set_layer('green')
my_step_exporter.add_shape(my_sphere_shape)
my_step_exporter.write_file()

Pisanje datotek STL

Stereolitografski format je primeren za prikaz v spletnih pregledovalnikih (threejs z WebGL) saj vključuje zapis v trikotnikih. Ne vključuje barv in lahko izvozi le en Shape(). Da zmanjšamo velikost datoteke, namesto ASCII izberemo binarni format z "False". Naslednji primer shrani enotsko kroglo:

# -*- coding: utf-8 -*-
from OCC.StlAPI import *
from OCC.BRepPrimAPI import *
my_sphere_shape = BRepPrimAPI_MakeSphere(1).Shape()
stl_writer = StlAPI()
stl_writer.Write(my_sphere_shape, "krogla.stl", False)

Uporaba funkcije zaokrožitve, pozicioniranje valja na izbrano mesto, združevanje CAD modelov ter izvoz v STEP format

V naslednjem primeru so prikazane naslednje funkcije:

• zaokrožitve
• pozicioniranje elementa
• združevanje CAD modelov
• enostaven izvoz CAD modela v STEP format

##Copyright 2011 Simon Kulovec (simon.kulovec@lecad.si)
##This file is part of pythonOCC.

## Importanje razlicnih knjiznic

# Uporabniski vmesnik GUI
from OCC.Display.SimpleGui import *

# OpenCascade
from OCC.gp import *
from OCC.TopoDS import *
from OCC.GC import *
from OCC.BRepBuilderAPI import *
from OCC.BRepPrimAPI import *
from OCC.BRepFilletAPI import *
from OCC.BRepAlgoAPI import *
from OCC.Utils.Topology import *
from OCC.BRep import *
from OCC.Utils.DataExchange.STEP import STEPExporter

# OCC.Display.SimpleGui.init_display() returns multiple
# values which are assigned here
display, start_display, add_menu, add_function_to_menu = \
init_display()

# Definiranje spremenljivk
myWidth = 50.0
myThickness = 30.0
myHeight = 70.0

# Definiranje zacetnih tock
aPnt1 = gp_Pnt(-myWidth / 2. , 0 , 0)
aPnt2 = gp_Pnt(-myWidth / 2. , -myThickness / 4. , 0)
aPnt3 = gp_Pnt(0 , -myThickness / 2. , 0)
aPnt4 = gp_Pnt(myWidth / 2. , -myThickness / 4. , 0)
aPnt5 = gp_Pnt(myWidth / 2. , 0 , 0)

# Definiranje geometrije
aArcOfCircle = GC_MakeArcOfCircle(aPnt2,aPnt3 ,aPnt4)
aSegment1 = GC_MakeSegment(aPnt1 , aPnt2)
aSegment2 = GC_MakeSegment(aPnt4 , aPnt5)

# Definiranje topologije
aEdge1 = BRepBuilderAPI_MakeEdge(aSegment1.Value())
aEdge2 = BRepBuilderAPI_MakeEdge(aArcOfCircle.Value())
aEdge3 = BRepBuilderAPI_MakeEdge(aSegment2.Value())
aWire  = BRepBuilderAPI_MakeWire(aEdge1.Edge() , aEdge2.Edge() ,\
                                         aEdge3.Edge())

# Izdelava celotnega profila - mirror

xAxis = gp_OX()
aTrsf = gp_Trsf()
aTrsf.SetMirror(xAxis)
aBRepTrsf = BRepBuilderAPI_Transform(aWire.Shape() , aTrsf)
aMirroredShape = aBRepTrsf.Shape()
aMirroredWire = TopoDS_wire(aMirroredShape)
mkWire = BRepBuilderAPI_MakeWire()
mkWire.Add(aWire.Wire())
mkWire.Add(aMirroredWire)
myWireProfile = mkWire.Wire()

# Telo: Iz profila se izdela telo
myFaceProfile = BRepBuilderAPI_MakeFace(myWireProfile)
aPrismVec = gp_Vec(0 , 0 , myHeight)
myBody = BRepPrimAPI_MakePrism(myFaceProfile.Face() , aPrismVec)

# Telo: Dodamo zaokrozitve (fillet)
mkFillet = BRepFilletAPI_MakeFillet(myBody.Shape())
topology_traverser = Topo(myBody.Shape())
for aEdge in topology_traverser.edges(): #z uporabo for zanke iščemo robove na CAD modelu in jih zaokrožujemo s funkcijo mkFillet in združujemo z .Add
    mkFillet.Add(myThickness / 12. , aEdge) #velikost zaokrožitve myThickness / 12.
myBody = mkFillet.Shape() #vse zaokrožitve priključimo k prvotni obliki myBody

# Dodajanje grla na steklenico (valj)
neckLocation = gp_Pnt(0, 0, myHeight) #Določitev lokacije valja
neckNormal = gp_DZ() #smer normale, v katero bomo valj izvlekli
neckAx2 = gp_Ax2(neckLocation, neckNormal) 

myNeckRadius = myThickness / 4 #radij valja
myNeckHeight = myHeight / 10 # višina valja

mkCylinder = BRepPrimAPI_MakeCylinder(neckAx2 , myNeckRadius , \
                                          myNeckHeight)
myNeck = mkCylinder.Shape();

myBody = BRepAlgoAPI_Fuse(myBody, myNeck) #dodajanje valja k obliki myBody

# Izdelava sestava
aRes = TopoDS_Compound() #Določitev spremenljivke za sestav
aBuilder = BRep_Builder()
aBuilder.MakeCompound (aRes)
aBuilder.Add (aRes, myBody.Shape()) #Dodajanje različnih oblik v sestav aRes

# Export to STEP ()
my_step_exporter = STEPExporter("export_step_file.stp") #Določevanje imena STEP file.a 
my_step_exporter.add_shape(aRes) #Dodajanje oblike v STEP file
my_step_exporter.write_file()

# Izris oblike
display.EraseAll()
print dir(display)
display.DisplayShape(aRes)

start_display()

Povzetek druge vaje

Izdelava CAD kocke z predhodno definiranimi točkami (Uporaba for zanke za generiranje točk, površin, mreže)

import sys
from OCC.Display.SimpleGui import *

from OCC.gp import gp_Pnt
from OCC.GC import GC_MakeSegment
from OCC.BRepBuilderAPI import \
  BRepBuilderAPI_MakeEdge, BRepBuilderAPI_MakeFace, BRepBuilderAPI_MakeWire,\
  BRepBuilderAPI_MakeShell, BRepBuilderAPI_MakeSolid
from OCC.BRep import BRep_Builder
from OCC.TopoDS import TopoDS_Shell, TopoDS_Solid
from OCC import StlAPI

mesh = {
  "vertices":[[-0.2,-0.2,0.2],[0.2,-0.2,0.2],[0.2,0.2,0.2],[-0.2,0.2,0.2],\
                  [-0.2,-0.2,0.6000000000000001],[0.2,-0.2,0.6000000000000001],\
                  [0.2,0.2,0.6000000000000001],[-0.2,0.2,0.6000000000000001]],
  "faces":[[3,2,1,0],[4,5,6,7],[7,6,2,3],[5,4,0,1],[6,5,1,2],[4,7,3,0]]
}

def main():

  vertices = [ gp_Pnt(p[0],p[1],p[2]) for p in mesh['vertices'] ]
  oFaces = []

  builder = BRep_Builder()
  shell = TopoDS_Shell()
  builder.MakeShell(shell)

  for face in mesh['faces']:
    edges = []
    face.reverse()
    for i in range(len(face)):
      cur = face[i]
      nxt = face[(i+1)%len(face)]
      segment = GC_MakeSegment(vertices[cur],vertices[nxt])
      edges.append(BRepBuilderAPI_MakeEdge(segment.Value()))

    wire = BRepBuilderAPI_MakeWire()
    for edge in edges:
      wire.Add(edge.Edge())

    oFace = BRepBuilderAPI_MakeFace(wire.Wire())

    builder.Add(shell, oFace.Shape())
    display.DisplayShape(shell)

if __name__ == '__main__':
    display, start_display, add_menu, add_function_to_menu = \
        init_display()
    main()
    start_display()

Branje vrednosti iz datoteke (input_file.dat) in generiranje CAD modela (Parametriziran CAD model)

Datoteka: input_file.dat

70 70 70

Programska koda (.py)

#Odpiranje datoteke input_file.dat, ter branje iz nje v izbrane spremenljivke
#Simon Kulovec
from OCC.Display.SimpleGui import *
from OCC.BRepPrimAPI import *

display, start_display, add_menu, add_function_to_menu = init_display()

#Branje iz datoteke: input_file.dat
f= open("input_file.dat", "r")
lines = f.readlines()
box0 = [] #Vektor v katerega shranjujemo prebrane vrednosti

#Stevilo prebranih vrstic je 1
for i in range(1): 
    x,y,z=[eval(s) for s in lines[i].split(" ")]
    box0.append(x)
    box0.append(y)
    box0.append(z)
    #Izpis prebranih vrednosti iz datoteke v terminal
    print "%4.1f %4.1f %4.1f "  % ( box0[i], box0[i+1],\
                                        box0[i+2])
f.close()


my_box = BRepPrimAPI_MakeBox(box0[0],box0[1],box0[2]).Shape()

display.DisplayShape(my_box)
start_display()

Prikaz izdelave kocke in uporaba funkcije krožnega izvleka

##Prikaz izdelave kocke in uporaba funkcije krožnega izvleka
##S.Kulovec, 2011

from OCC.gp import *
from OCC.BRepPrimAPI import *
from OCC.TopExp import *
from OCC.TopAbs import *
import OCC.TopoDS
from OCC.BRep import *
from OCC.Geom import *
from OCC.GCE2d import *
from OCC.Geom2d import *
from OCC.BRepLib import *
from OCC.BRepFeat import *

from OCC.Utils.Topology import Topo
from OCC.BRepBuilderAPI import *

import sys, time
from OCC.Display.SimpleGui import *
display, start_display, add_menu, add_function_to_menu = init_display()

S = BRepPrimAPI_MakeBox(400.,250.,300.).Shape()
faces = list(Topo(S).faces())
F1 = faces[2]
surf = BRep_Tool_Surface(F1)
Pl = Handle_Geom_Plane_DownCast(surf)

D = gp.gp_OX()

MW1 = BRepBuilderAPI_MakeWire() 
p1 = gp_Pnt2d(100.,100.)
p2 = gp_Pnt2d(200.,100.)
aline = GCE2d_MakeLine(p1,p2).Value()
MW1.Add(BRepBuilderAPI_MakeEdge(aline,surf,0.,p1.Distance(p2)).Edge())

p1 = gp_Pnt2d(200.,100.)
p2 = gp_Pnt2d(150.,200.)
aline = GCE2d_MakeLine(p1,p2).Value()
MW1.Add(BRepBuilderAPI_MakeEdge(aline,surf,0.,p1.Distance(p2)).Edge())

p1 = gp_Pnt2d(150.,200.)
p2 = gp_Pnt2d(100.,100.)
aline = GCE2d_MakeLine(p1,p2).Value()
MW1.Add(BRepBuilderAPI_MakeEdge(aline,surf,0.,p1.Distance(p2)).Edge())

MKF1 = BRepBuilderAPI_MakeFace() 
MKF1.Init(surf,False)
MKF1.Add(MW1.Wire())
FP = MKF1.Face()
BRepLib_BuildCurves3d(FP)
MKrev = BRepFeat_MakeRevol(S,FP,F1,D,1,True)
F2 = faces[4]
MKrev.Perform(F2)
display.EraseAll()
display.DisplayShape(MKrev.Shape())

start_display()

Napotki

Q: Zanima me kako se v PythonOCC dela luknje oz izvrtine(ali izreze). Katere funkcije se uporablja?

A: Podobno kot fuse je za izreze cut.

import OCC.Utils.Construct as construct
drzalo = construct.boolean_fuse(roka,nosilec) #celoten sestav
drzalo = construct.boolean_cut(drzalo, izvrtina)

Boolove operacije.

Q: Rad bi zaokrožil le robove profila, ne pa tudi prereza.

A: Če želimo zaokrožiti le določene robove lahko uporabimo različne teste. Naslednji primer naredi kopijo stebra in v zanki preiskovalca topologije dodaja robove, ki jih je potrebno zaokrožiti tako, da preverja višino začetne in končne točke robu. V primeru, da točki nisti v ravnini (X,Y) ga zaokroži. Velikost zaokrožitve je lahko največ tolikšna, da se še da normalno zaokrožiti označene robove.

# Telo: Dodamo zaokrožitve (fillet)
mkFillet = BRepFilletAPI_MakeFillet(steber.Shape())
topology_traverser = Topo(steber.Shape())
for aEdge in topology_traverser.edges():
    first, last = TopExp().FirstVertex(aEdge), TopExp().LastVertex(aEdge)
    first_vert, last_vert = BRep_Tool().Pnt(first), BRep_Tool().Pnt(last)
    if first_vert.Z() != last_vert.Z():
        mkFillet.Add(1.2, aEdge)
display.DisplayShape(mkFillet.Shape())        

Q: Kako postavimo model v drugi položaj?

A: Okoli osi v prostoru lahko rotirate:

    LokacijaOsi1 = gp_Pnt(8, 45, -100) 
    RotacijaOs1 = gp_Ax1(LokacijaOsi1, gp_Dir(0,0,1)) #Os rotacije
    TransfRot1 = gp_Trsf()
    TransfRot1.SetRotation(RotacijaOs1, t1)
    J19 = BRepBuilderAPI_Transform(J18, TransfRot1).Shape()

Translacija je še lažja:

    Premik = gp_Vec(-130, -870, -2530)
    Translacija = gp_Trsf()
    Translacija.SetTranslation(Premik)
    rezultat = BRepBuilderAPI_Transform(J17, Translacija).Shape()

Ostale funkcije so opisane v ​http://api.pythonocc.org/OCC.gp.gp_Trsf-class.html

Prikaz torus modela v brskalniku

#!/usr/bin/env python

##Copyright 2009-2014 Thomas Paviot (tpaviot@gmail.com)
##
##This file is part of pythonOCC.
##
##pythonOCC is free software: you can redistribute it and/or modify
##it under the terms of the GNU Lesser General Public License as published by
##the Free Software Foundation, either version 3 of the License, or
##(at your option) any later version.
##
##pythonOCC is distributed in the hope that it will be useful,
##but WITHOUT ANY WARRANTY; without even the implied warranty of
##MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
##GNU Lesser General Public License for more details.
##
##You should have received a copy of the GNU Lesser General Public License
##along with pythonOCC.  If not, see <http://www.gnu.org/licenses/>.

from OCC.Display.WebGl import threejs_renderer
from OCC.BRepPrimAPI import BRepPrimAPI_MakeTorus

torus_shp = BRepPrimAPI_MakeTorus(20., 10.).Shape()
my_renderer = threejs_renderer.ThreejsRenderer(background_color="#123345")
my_renderer.DisplayShape(torus_shp)

Povezave in navodila za modeliranje z OCCT

• ​PythonOCC API’s dokumentacija na spletni strani
• ​Primeri PythonOCC
• Vizualizacija s PythonOCC -- v obliki PDF
• Modelling algorithms za OpenCASCADE 6.6
• Modelling data