pythonocc基础使用：1.读取/写入brep，iges，step，stl文件

灰太狼 2022-04-06 15:58 1069阅读 0赞

## **总目录** >> [PythonOCC入门进阶到实战][PythonOCC](目前已更新入门篇、基础篇和进阶篇) ##

--------------------

**由作者实现的国产云端CAD** [**www.yuntucad.com**][www.yuntucad.com]

对于cad系统的开发，读入外界的文件很重要。  
目前OCC开发者已经支持快速读入brep,igs,stp,stl格式了（但是这部分的资源目前还未同步到0.18.1版本），具体使用方法见下

### 1.读取/写入 brep 格式文件 ###

brep作为opencascade官方推出的格式，内核对其解析会更快。  
参考：https://www.opencascade.com/doc/occt-7.3.0/overview/html/occt\_user\_guides\_\_brep\_wp.html

##brep作为occ原生的格式，加载速度快，需要特别注意。
    from OCC.Core.BRepPrimAPI import BRepPrimAPI_MakeBox
    from OCC.Display.SimpleGui import init_display
    from OCC.Core.BRepTools import breptools_Read,breptools_Write
    from OCC.Core.TopoDS import TopoDS_Shape
    from OCC.Core.BRep import BRep_Builder
    
    
    # 建造一个正方体，并写入brep
    box_shp = BRepPrimAPI_MakeBox(10, 20, 20).Shape()
    
    breptools_Write(box_shp,'box.brep')
    print("已经成功写入brep")
    
    #读入一个brep
    read_box = TopoDS_Shape()
    builder = BRep_Builder()
    breptools_Read(read_box, 'box.brep', builder)
    
    
    
    display, start_display, add_menu, add_function_to_menu = init_display()
    display.DisplayShape(read_box, update=True)
    start_display()

### 2.读取/写入 iges，step，stl格式文件 ###

from OCC.Display.SimpleGui import init_display
    from OCC.Extend.DataExchange import read_iges_file,read_step_file,read_stl_file
    shapes=read_iges_file(fileName1)
    #shapes=read_step_file(fileName1)
    #shapes=read_stl_file(fileName1)
    display, start_display, add_menu, add_function_to_menu = init_display()
    display.DisplayShape(shapes, update=True)

如果你懒得去找官方写的资源，我下面也会展示read\_iges\_file，read\_step\_file，read\_stl\_file函数是如何定义的：  
***read\_iges\_file函数***

def read_iges_file(filename, return_as_shapes=False, verbosity=False):
        """ read the IGES file and returns a compound
        filename: the file path
        return_as_shapes: optional, False by default. If True returns a list of shapes,
                          else returns a single compound
        verbosity: optionl, False by default.
        """
    
        assert os.path.isfile(filename)
    
        iges_reader = IGESControl_Reader()
        status = iges_reader.ReadFile(filename)
    
        _shapes = []
    
        if status == IFSelect_RetDone:  # check status
            if verbosity:
                failsonly = False
                iges_reader.PrintCheckLoad(failsonly, IFSelect_ItemsByEntity)
                iges_reader.PrintCheckTransfer(failsonly, IFSelect_ItemsByEntity)
            iges_reader.TransferRoots()
            nbr = iges_reader.NbRootsForTransfer()
            for n in range(1, nbr+1):
                nbs = iges_reader.NbShapes()
                if nbs == 0:
                    print("At least one shape in IGES cannot be transfered")
                elif nbr == 1 and nbs == 1:
                    a_res_shape = iges_reader.Shape(1)
                    if a_res_shape.IsNull():
                        print("At least one shape in IGES cannot be transferred")
                    else:
                        _shapes.append(a_res_shape)
                else:
                    for i in range(1, nbs+1):
                        a_shape = iges_reader.Shape(i)
                        if a_shape.IsNull():
                            print("At least one shape in STEP cannot be transferred")
                        else:
                            _shapes.append(a_shape)
        # if not return as shapes
        # create a compound and store all shapes
        if not return_as_shapes:
            builder = BRep_Builder()
            compound = TopoDS_Compound()
            builder.MakeCompound(compound)
            for s in _shapes:
                builder.Add(compound, s)
            _shapes = compound
        return _shapes

***read\_step\_file函数***

def read_step_file(filename, return_as_shapes=False, verbosity=False):
        """ read the STEP file and returns a compound
        filename: the file path
        return_as_shapes: optional, False by default. If True returns a list of shapes,
                          else returns a single compound
        verbosity: optionl, False by default.
        """
        assert os.path.isfile(filename)
    
        step_reader = STEPControl_Reader()
        status = step_reader.ReadFile(filename)
    
        if status == IFSelect_RetDone:  # check status
            if verbosity:
                failsonly = False
                step_reader.PrintCheckLoad(failsonly, IFSelect_ItemsByEntity)
                step_reader.PrintCheckTransfer(failsonly, IFSelect_ItemsByEntity)
            ok = step_reader.TransferRoot(1)
            _nbs = step_reader.NbShapes()
            shape_to_return = step_reader.Shape(1)  # a compound
            assert not shape_to_return.IsNull()
        else:
            raise AssertionError("Error: can't read file.")
        if return_as_shapes:
            shape_to_return = TopologyExplorer(shape_to_return).solids()
    
        return shape_to_return

***read\_stl\_file函数***

def read_stl_file(filename):
        """ opens a stl file, reads the content, and returns a BRep topods_shape object
        """
        assert os.path.isfile(filename)
    
        stl_reader = StlAPI_Reader()
        the_shape = TopoDS_Shape()
        stl_reader.Read(the_shape, filename)
    
        assert not the_shape.IsNull()
    
        return the_shape

[PythonOCC]: https://blog.csdn.net/weixin_42755384/article/details/87893697
[www.yuntucad.com]: https://www.yuntucad.com