OpenCasCade由一个基础形状拉伸形成其它形状的问题

àì夳堔傛蜴生んèń 2022-03-14 14:56 463阅读 0赞

使用OCC有一段时间了，一直没有记录这方面的内容，为了以后的学习，决定整理一下（技术有限，错误请指正）。

OCC版本：6.8.0

操作系统：windows（7）

开发工具：vs2010，vs2017

UI框架：MFC

如题，今天的问题是关于OCC如何由一个基础的形状，通过拉伸，形成另一种图形，即三维视角。

OCC源码里面提供了MFC有关的很多例子，这对我来说是一个很好的学习资源，好多问题都是从例子源码里面的到的思路，

关于这个问题也是在稍微有点头绪的情况下去找的例子，这些都是惨不忍睹的探索过程，国内这方面的资料也不是很多，通过不断寻找找到了简单的实现方法那就是：BRepPrimAPI\_MakePrism类

这个类在OCC头文件BRepPrimAPI\_MakePrism.hxx 中

这里只看一下头文件，具体的实现源码就看个人兴趣爱好了，

BRepPrimAPI\_MakePrism.hxx 如下，全是导出函数，注释都是英文的（能看尽量自己阅读英文，不行就谷歌翻译吧）

// This file is generated by WOK (CPPExt).
    // Please do not edit this file; modify original file instead.
    // The copyright and license terms as defined for the original file apply to 
    // this header file considered to be the "object code" form of the original source.
    
    #ifndef _BRepPrimAPI_MakePrism_HeaderFile
    #define _BRepPrimAPI_MakePrism_HeaderFile
    
    #include <Standard.hxx>
    #include <Standard_DefineAlloc.hxx>
    #include <Standard_Macro.hxx>
    
    #include <BRepSweep_Prism.hxx>
    #include <BRepPrimAPI_MakeSweep.hxx>
    #include <Standard_Boolean.hxx>
    class TopoDS_Shape;
    class gp_Vec;
    class gp_Dir;
    class BRepSweep_Prism;
    class TopTools_ListOfShape;
    
    
    //! Describes functions to build linear swept topologies, called prisms.
    //! A prism is defined by:
    //! -   a basis shape, which is swept, and
    //! -   a sweeping direction, which is:
    //! -   a vector for finite prisms, or
    //! -   a direction for infinite or semi-infinite prisms.
    //! The basis shape must not contain any solids.
    //! The profile generates objects according to the following rules:
    //! -   Vertices generate Edges
    //! -   Edges generate Faces.
    //! -   Wires generate Shells.
    //! -   Faces generate Solids.
    //! -   Shells generate Composite Solids
    //! A MakePrism object provides a framework for:
    //! -   defining the construction of a prism,
    //! -   implementing the construction algorithm, and
    //! -   consulting the result.
    class BRepPrimAPI_MakePrism  : public BRepPrimAPI_MakeSweep
    {
    public:
    
      DEFINE_STANDARD_ALLOC
    
      
      //! Builds the prism of base S and vector V. If C is true,
      //! S is copied. If Canonize is true then generated surfaces
      //! are attempted to be canonized in simple types
      Standard_EXPORT BRepPrimAPI_MakePrism(const TopoDS_Shape& S, const gp_Vec& V, const Standard_Boolean Copy = Standard_False, const Standard_Boolean Canonize = Standard_True);
      
      //! Builds a semi-infinite or an infinite prism of base S.
      //! If Inf is true the prism  is infinite, if Inf is false
      //! the prism is semi-infinite (in the direction D).  If C
      //! is true S is copied (for semi-infinite prisms).
      //! If Canonize is true then generated surfaces
      //! are attempted to be canonized in simple types
      Standard_EXPORT BRepPrimAPI_MakePrism(const TopoDS_Shape& S, const gp_Dir& D, const Standard_Boolean Inf = Standard_True, const Standard_Boolean Copy = Standard_False, const Standard_Boolean Canonize = Standard_True);
      
      //! Returns the internal sweeping algorithm.
      Standard_EXPORT  const  BRepSweep_Prism& Prism()  const;
      
      //! Builds the resulting shape (redefined from MakeShape).
      Standard_EXPORT virtual   void Build() ;
      
      //! Returns the  TopoDS  Shape of the bottom of the prism.
      Standard_EXPORT   TopoDS_Shape FirstShape() ;
      
      //! Returns the TopoDS Shape of the top of the prism.
      //! In the case of a finite prism, FirstShape returns the
      //! basis of the prism, in other words, S if Copy is false;
      //! otherwise, the copy of S belonging to the prism.
      //! LastShape returns the copy of S translated by V at the
      //! time of construction.
      Standard_EXPORT   TopoDS_Shape LastShape() ;
      
      //! Returns ListOfShape from TopTools.
      Standard_EXPORT virtual  const  TopTools_ListOfShape& Generated (const TopoDS_Shape& S) ;
      
      //! Returns the TopoDS Shape of the bottom  of the  prism.
      //! generated  with  theShape (subShape of the  generating shape).
      Standard_EXPORT   TopoDS_Shape FirstShape (const TopoDS_Shape& theShape) ;
      
      //! Returns the  TopoDS  Shape of the top  of  the  prism.
      //! generated  with  theShape (subShape of the  generating shape).
      Standard_EXPORT   TopoDS_Shape LastShape (const TopoDS_Shape& theShape) ;
    
    protected:
    
    
    
    private:
    
      BRepSweep_Prism myPrism;
    
    
    };
    
    
    #endif // _BRepPrimAPI_MakePrism_HeaderFile

这个头文见虽然不算长，但内容还是挺多的。

回到正题，根据今天的问题，首先要构造一个基础图形，何为基础图形，看一下头文件，BRepPrimAPI\_MakePrism类的两个构造函数，这两个函数就是实现将一个基础图形向着某一个方向拉伸，具体拉伸的长度，有几方法实现。

我这里主要是用的是第一个构造函数，其他的一些方法可以获取一些拉伸后图形的基本元素等，可以结合自身情况查阅注释使用。

下面是第一个构造函数：

Standard_EXPORT BRepPrimAPI_MakePrism(const TopoDS_Shape& S, const gp_Vec& V, const Standard_Boolean Copy = Standard_False, const Standard_Boolean Canonize = Standard_True);

**const TopoDS\_Shape& S**：第一个参数，类型是TopoDS\_Shape，也是一个类，这个其实就是我们所说的基本形状。

在OCC里面可以是以下几种：

TopoDS\_Edge（边，可以自己由两点构成）

TopoDS\_Wire（由边组成的线框，可以自己在三维空间生成点，点构成边，然后构成线框）

TopoDS\_Face（面，可以由自定义线框构成，也可以采用现有的OCC API生成）

**const gp\_Vec& V：**第二个参数，类型是gp\_Vec，也是一个类，这个主要就是指定拉伸方向，有几种实现方式，可以在类的头文件里看一下，我选择的是一种比较直观的方法，直接在Z轴方向拉伸，在下面代码中。

其他几个参数可以不写，有默认值，如果需要做进一步编辑，可以看一下英文注释。

下面是我在项目代码中的使用例子：

BRepBuilderAPI_MakeWire mkw;
    	TopoDS_Edge E11 = BRepBuilderAPI_MakeEdge(gp_Pnt(40.,0.,0.), gp_Pnt(82.5,25.,0.));
    	TopoDS_Edge E12 = BRepBuilderAPI_MakeEdge(gp_Pnt(82.5,25.,0.), gp_Pnt(42.5,93.,0.));
    	TopoDS_Edge E13 = BRepBuilderAPI_MakeEdge(gp_Pnt(42.5,93.,0.), gp_Pnt(0.,68.,0.));
    	TopoDS_Edge E14 = BRepBuilderAPI_MakeEdge(gp_Pnt(0.,68.,0.), gp_Pnt(40.,0.,0.));
    	TopoDS_Wire W1 = BRepBuilderAPI_MakeWire(E11,E12,E13,E14);
    
    	//TopoDS_Shape S = BRepPrimAPI_MakePrism(W1,gp_Vec(0.,0.,50));                          //线框TopoDS_Wire在指定向量拉伸
    	//TopoDS_Shape S = BRepPrimAPI_MakePrism(E14,gp_Vec(0.,0.,50));                           //边TopoDS_Edge在指定向量拉伸
    	TopoDS_Shape S =BRepPrimAPI_MakePrism(BRepBuilderAPI_MakeFace(W1),gp_Vec(0.,0.,50));   //面TopoDS_Face在指定向量拉伸
    	Handle(AIS_Shape) ais1 = new AIS_Shape(S);                                                
    	
    	
    	myAISContext->SetColor(ais1,Quantity_NOC_CYAN2,Standard_False); 
    	myAISContext->SetMaterial(ais1,Graphic3d_NOM_PLASTIC,Standard_False);   
    	myAISContext->Display(ais1,Standard_False);
    	myAISContext->SetCurrentObject(ais1,Standard_False);
    	Fit();

**下面看一下拉伸后的效果（部分图形因为鼠标旋转可能位置不是比较一致，旋转一下位置即可）**

**第一种：**由基础图形（面）拉伸成长方体：

基础图形面如下：

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzIyNjQyMjM5_size_16_color_FFFFFF_t_70][]

拉伸后的三维图形如下：

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzIyNjQyMjM5_size_16_color_FFFFFF_t_70 1][]

**第二种：**由基础图形（边）拉伸成面：

基础边如下：

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzIyNjQyMjM5_size_16_color_FFFFFF_t_70 2][]

拉伸后的面如下：

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzIyNjQyMjM5_size_16_color_FFFFFF_t_70 3][]

**第三种：**由基础图形（线框）拉伸成实体：

基础线框如下：

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzIyNjQyMjM5_size_16_color_FFFFFF_t_70 4][]

拉伸后的实体如下：

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzIyNjQyMjM5_size_16_color_FFFFFF_t_70 5][]

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[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzIyNjQyMjM5_size_16_color_FFFFFF_t_70 1]: /images/20220312/eb5ab0c0f5d0494694067edebf91f65e.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzIyNjQyMjM5_size_16_color_FFFFFF_t_70 2]: /images/20220312/baa599105d0743f194bd5de91aa941ca.png
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