OpenCasCade部分API剖析--入门tutorial

约定不等于承诺〃 2022-03-01 00:10 521阅读 0赞

Tutorial简述

gp_XXX
    Standard_XXX
    Geom_XXX
    GC_MakeXXX
    TopoDS_XXX
    BRepBuilderAPI_XXX
    BRepPrimAPI_XXX
    BRepFilletAPI_XXX
    TopExp_Explorer
    TopAbs_ShapeEnum
    BRepAlgoAPI_XXX
    BRep_Tool与 Standard_Transient
    TopTools_XXX
    BRepOffsetAPI_XXX

Tutorial源代码  
OCC接触两年有余了，以前使用频率不高，好多东西一知半解，现在是需要用到它的时候了。

**Tutorial简述**  
Tutorial用一个绘制Bottle的例子描述了OCC建模的基本步骤。这里涉及了一些概念和类的用法，不细心看做笔记是很容易忘掉的。

**gp\_XXX**  
gp\_Pnt 是最简单的“点”；此外对应的有还有许多这样的简单结构,这些类从其类名就可以知道它可能有哪些参数，没错，这些类包含了点、线、面、轴以及各种曲面等，其中的参数都是构建这些几何结构必须的参数，我们可以称gp\_Pnt这一类的类为基本几何类。  
——————————————————————————————

- gp_Ax2 
    - gp_Ax2d 
    - gp_Ax3 
    - gp_Ax3d 
    - gp_Ax22 
    - gp_Ax22d 
    - gp_Circ 
    - gp_Circ2d 
    - gp_Cone 
    - gp_Cylinder 
    - gp_Dir 
    - gp_Dir2d 
    - gp_Elips 
    - gp_Elips2d 
    - gp_EulerSequence 
    - gp_GTrsf 
    - gp_GTrsf2d 
    - gp_Hypr 
    - gp_Hypr2d 
    - gp_Lin 
    - gp_Lin2d 
    - gp_Mat 
    - gp_Mat2d 
    - gp_Parab 
    - gp_Parab2d 
    - gp_Pln 
    - gp_Pnt2d 
    - gp_Quaternion 
    - gp_QuaternionNLerp 
    - gp_QuaternionSLerp 
    - gp_Sphere 
    - gp_Torus 
    - gp_Trsf 
    - gp_Trsf2d 
    - gp_TrsfForm 
    - gp_TrsfNLerp 
    - gp_Vec 
    - gp_Vec2d 
    - gp_VectorWithNullMagnitude 
    - gp_XY 
    - gp_XYZ

**Standard\_XXX**  
Standard\_XXX类型的类是OCC的类型定义、宏定义的数据结构，与我们常用的C++没有区别的，我们可以称其为OCC定义数值类型。

#define Standard_False false
    #define Standard_True  true
    typedef int           Standard_Integer;
    typedef double        Standard_Real;
    typedef bool          Standard_Boolean;
    typedef float         Standard_ShortReal;
    typedef char          Standard_Character;
    typedef unsigned char Standard_Byte;
    typedef void*         Standard_Address;
    typedef size_t        Standard_Size;
    typedef std::time_t   Standard_Time;
    
    // Unicode primitives, char16_t, char32_t
    typedef char          Standard_Utf8Char;     //!< signed   UTF-8 char
    typedef unsigned char Standard_Utf8UChar;    //!< unsigned UTF-8 char

**Geom\_XXX**  
Geom定义了几何数据结构，但也仅此而已，并不包含什么算法，可以说它是由gp\_XXX构建而成的数据结构，比gp\_XXX高级一些。我们可以称其为构建几何类。  
——————————————————————————————

Geom_Axis1Placement 
    Geom_Axis2Placement 
    Geom_AxisPlacement 
    Geom_BezierCurve 
    Geom_BezierSurface 
    Geom_BoundedCurve 
    Geom_BoundedSurface 
    Geom_BSplineCurve 
    Geom_BSplineSurface 
    Geom_CartesianPoint 
    Geom_Circle 
    Geom_Conic 
    ……

**GC\_MakeXXX**  
GC\_MakeXXX由简单的几何数据结构构建复杂的、常见的、带参数的几何结构Geom\_XXX，它主要包含的就是构建算法，我们可以称其为几何形状构建包，构建的结果是指向Geom\_XXX的指针。  
——————————————————————————————

GC_MakeArcOfCircle 
    GC_MakeArcOfEllipse 
    GC_MakeArcOfHyperbola 
    GC_MakeArcOfParabola 
    GC_MakeCircle 
    GC_MakeConicalSurface 
    GC_MakeCylindricalSurface 
    GC_MakeEllipse 
    GC_MakeHyperbola. 
    GC_MakeLine 
    GC_MakeMirror 
    GC_MakePlane 
    GC_MakeRotation 
    GC_MakeScale 
    GC_MakeSegment 
    GC_MakeTranslation 
    GC_MakeTrimmedCone 
    GC_MakeTrimmedCylinder 
    GC_Root
    
    Handle(Geom_TrimmedCurve) aArcOfCircle = GC_MakeArcOfCircle(aPnt2,aPnt3,aPnt4);

**TopoDS\_XXX**  
TopoDS\_XXX比Geom\_XXX再高一级，是多个Geom\_XXX的一种组合。每一个TopoDS\_XXX类都继承至TopoDS\_Shape。我们可以称这一层为几何拓扑结构。包含了拓扑点、线、面、体等简单的、复杂的几何拓扑结构。注意：这层也只是数据结构，并不包含算法。  
——————————————————————————————

TopoDS_AlertWithShape 
    TopoDS_Builder 
    TopoDS_Compound 
    TopoDS_CompSolid 
    TopoDS_Edge 
    TopoDS_Face 
    TopoDS_FrozenShape 
    TopoDS_HShape 
    TopoDS_Iterator 
    TopoDS_ListIteratorOfListOfShape 
    TopoDS_ListOfShape 
    TopoDS_LockedShape 
    TopoDS_Shape 
    TopoDS_Shell 
    TopoDS_Solid 
    TopoDS_TCompound 
    TopoDS_TCompSolid 
    TopoDS_TEdge 
    TopoDS_TFace 
    TopoDS_TShape 
    TopoDS_TShell 
    TopoDS_TSolid 
    TopoDS_TVertex 
    TopoDS_TWire 
    TopoDS_UnCompatibleShapes 
    TopoDS_Vertex 
    TopoDS_Wire

**BRepBuilderAPI\_XXX**  
前边说了TopoDS\_XXX只是数据结构，那么如何由Geom\_XXX构建TopoDS\_XXX呢，这就是BRepBuilderAPI\_XXX的工作了。我们可以称这一层为拓扑结构构建包。它的返回值直接就是TopoDS\_XXX。

此外这一部分有好多需要注意的事项:

通过矩阵变换获取拓扑结构  
通过向下转型(TopoDS::XXX)获取拓扑结构  
通过TopoDS的组合获取TopoDS结构  
也就是说：这一步骤相当于使用一个CAD、SolidWorks等的造型软件。熟悉造型的功能，想必更熟悉这部分要完成的工作。——————————————————————————————

BRepBuilderAPI_BndBoxTreeSelector 
    BRepBuilderAPI_CellFilter 
    BRepBuilderAPI_Collect 
    BRepBuilderAPI_Command 
    BRepBuilderAPI_Copy 
    BRepBuilderAPI_EdgeError 
    BRepBuilderAPI_FaceError 
    BRepBuilderAPI_FastSewing 
    BRepBuilderAPI_FindPlane 
    BRepBuilderAPI_GTransform 
    BRepBuilderAPI_MakeEdge 
    BRepBuilderAPI_MakeEdge2d 
    BRepBuilderAPI_MakeFace 
    BRepBuilderAPI_MakePolygon 
    BRepBuilderAPI_MakeShape 
    BRepBuilderAPI_MakeShell 
    BRepBuilderAPI_MakeSolid 
    BRepBuilderAPI_MakeVertex 
    BRepBuilderAPI_MakeWire 
    BRepBuilderAPI_ModifyShape 
    BRepBuilderAPI_NurbsConvert 
    BRepBuilderAPI_PipeError 
    BRepBuilderAPI_Sewing 
    BRepBuilderAPI_ShapeModification 
    BRepBuilderAPI_ShellError 
    BRepBuilderAPI_Transform 
    BRepBuilderAPI_TransitionMode 
    BRepBuilderAPI_VertexInspector 
    BRepBuilderAPI_WireError
    
    TopoDS_Edge aEdge1 = BRepBuilderAPI_MakeEdge(aSegment1); 
    TopoDS_Edge aEdge2 = BRepBuilderAPI_MakeEdge(aArcOfCircle); 
    TopoDS_Edge aEdge3 = BRepBuilderAPI_MakeEdge(aSegment2);

**BRepPrimAPI\_XXX**  
这一层包的功能是把之前的拓扑结构建立成实体，它们构建的结果当然也是拓扑结果的TopoDS\_XXX。我们可以称这一层为实体构建包，拓扑构建满足以下的规律：

形状 生成形状  
顶点(vertex) 边(edge)  
边(edge) 面(face)  
线(wire) 壳(shell)  
面(face) 体(solid)  
壳(shell) 组合体(compound of solids)  
——————————————————————————————

BRepPrimAPI_MakeBox 
    BRepPrimAPI_MakeCone 
    BRepPrimAPI_MakeCylinder 
    BRepPrimAPI_MakeHalfSpace 
    BRepPrimAPI_MakeOneAxis 
    BRepPrimAPI_MakePrism 
    BRepPrimAPI_MakeRevol 
    BRepPrimAPI_MakeRevolution 
    BRepPrimAPI_MakeSphere 
    BRepPrimAPI_MakeSweep 
    BRepPrimAPI_MakeTorus 
    BRepPrimAPI_MakeWedge

**BRepFilletAPI\_XXX**  
倒角包：计算倒角。  
——————————————————————————————

BRepFilletAPI_LocalOperation 
    BRepFilletAPI_MakeChamfer 
    BRepFilletAPI_MakeFillet 
    BRepFilletAPI_MakeFillet2d

**TopExp\_Explorer**  
这个类比较特殊，专门用于TopoDS\_XXX的解析的，就是将已知实体(拓扑结构)解析为边组合、面组合等等。我们可以称其为拓扑解析包。

for(TopExp_Explorer aFaceExplorer(myBody, TopAbs_FACE) ; aFaceExplorer.More() ; aFaceExplorer.Next())
    { 
        TopoDS_Face aFace = TopoDS::Face(aFaceExplorer.Current()); 
    }

**TopAbs\_ShapeEnum**  
这也是一个特殊的结构，类似一个拓扑结构的数组，具有.More().Next().Current()三个重要的方法，我们可以称其为拓扑解析结果集。

**BRepAlgoAPI\_XXX**  
这个是核心算法包，专门用于Shape的交common(Boolean intersection)、差cut(Boolean subtraction)、和fuse(Boolean union)的计算。底层采用的是布尔操作。我们可以称其为几何算法包。  
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BRepAlgoAPI_Algo 
    BRepAlgoAPI_BooleanOperation 
    BRepAlgoAPI_BuilderAlgo 
    BRepAlgoAPI_Check 
    BRepAlgoAPI_Common 
    BRepAlgoAPI_Cut 
    BRepAlgoAPI_Defeaturing 
    BRepAlgoAPI_Fuse 
    BRepAlgoAPI_Section 
    BRepAlgoAPI_Splitter

**BRep\_Tool与 Standard\_Transient**  
这个BRep\_Tool类主要有三个方法，用于从TopoDS\_XXX向Geom\_XXX转换。

TopoDS_Face -> Geom_Surface 
    TopoDS_Edge -> Geom_Curve 
    TopoDS_Vertex -> Geom_Point

而**Standard\_Transient**类主要有两个用途。  
**DynamicType** 函数用来获取 Handle(Geom\_Surface)的真实类型，因为Geom\_Surface有可能是任何一种面。  
IsKind 用来判断该类型是否是某个类的子类。

Handle(Geom_Surface) aSurface = BRep_Tool::Surface(aFace);
    
    if(aSurface->DynamicType() == STANDARD_TYPE(Geom_Plane))
    { 
        Handle(Geom_Plane) aPlane = Handle(Geom_Plane)::DownCast(aSurface);
        //
    }

**TopTools\_XXX**  
组。List，Array，Sequence等。

TopTools_Array1OfListOfShape 
    TopTools_Array1OfShape 
    TopTools_Array2OfShape 
    TopTools_DataMapIteratorOfDataMapOfIntegerListOfShape 
    TopTools_DataMapIteratorOfDataMapOfIntegerShape 
    ……

**BRepOffsetAPI\_XXX**  
非常有用的包，通俗点讲它的功能：如果你的线框模型可以生成实体，模型，那么它可以……里边是一个复杂而漫长的过程……我可以称他形体生成包

BRepOffsetAPI_ThruSections aTool(Standard_True); 
    aTool.AddWire(threadingWire1); 
    aTool.AddWire(threadingWire2); 
    aTool.CheckCompatibility(Standard_False); 
    TopoDS_Shape myThreading = aTool.Shape();

**Tutorial源代码**

TopoDS_Shape MakeBottle(const Standard_Real myWidth, const Standard_Real myHeight, const Standard_Real myThickness) 
    { 
        // Profile : Define Support Points 
        gp_Pnt aPnt2(-myWidth / 2., -myThickness / 4., 0); 
        gp_Pnt aPnt3(0, -myThickness / 2., 0); 
        gp_Pnt aPnt4(myWidth / 2., -myThickness / 4., 0); 
        gp_Pnt aPnt5(myWidth / 2., 0, 0);
        // Profile : Define the Geometry 
        Handle(Geom_TrimmedCurve) aSegment1 = GC_MakeSegment(aPnt1, aPnt2); 
        Handle(Geom_TrimmedCurve) aSegment2 = GC_MakeSegment(aPnt4, aPnt5);
        // Profile : Define the Topology 
        TopoDS_Edge anEdge1 = BRepBuilderAPI_MakeEdge(aSegment1); 
        TopoDS_Edge anEdge3 = BRepBuilderAPI_MakeEdge(aSegment2); 
        TopoDS_Wire aWire = BRepBuilderAPI_MakeWire(anEdge1, anEdge2, anEdge3);
        // Complete Profile 
        gp_Ax1 xAxis = gp::OX(); 
        gp_Trsf aTrsf;
        aTrsf.SetMirror(xAxis); 
        BRepBuilderAPI_Transform aBRepTrsf(aWire, aTrsf); 
        TopoDS_Wire aMirroredWire = TopoDS::Wire(aMirroredShape);
        BRepBuilderAPI_MakeWire mkWire; 
        mkWire.Add(aMirroredWire); 
        TopoDS_Wire myWireProfile = mkWire.Wire();
        // Body : Prism the Profile 
        TopoDS_Face myFaceProfile = BRepBuilderAPI_MakeFace(myWireProfile); 
        gp_Vec aPrismVec(0, 0, myHeight); 
        TopoDS_Shape myBody = BRepPrimAPI_MakePrism(myFaceProfile, aPrismVec);
        // Body : Apply Fillets 
        BRepFilletAPI_MakeFillet mkFillet(myBody); 
        TopExp_Explorer anEdgeExplorer(myBody, TopAbs_EDGE); 
        while(anEdgeExplorer.More())
        { 
            TopoDS_Edge anEdge = TopoDS::Edge(anEdgeExplorer.Current()); //Add edge to fillet algorithm 
            mkFillet.Add(myThickness / 12., anEdge); 
            anEdgeExplorer.Next(); 
        }
        myBody = mkFillet.Shape();
        // Body : Add the Neck 
        gp_Pnt neckLocation(0, 0, myHeight); 
        gp_Dir neckAxis = gp::DZ(); 
        gp_Ax2 neckAx2(neckLocation, neckAxis);
        Standard_Real myNeckRadius = myThickness / 4.; 
        Standard_Real myNeckHeight = myHeight / 10.;
        BRepPrimAPI_MakeCylinder MKCylinder(neckAx2, myNeckRadius, myNeckHeight); 
        TopoDS_Shape myNeck = MKCylinder.Shape();
        myBody = BRepAlgoAPI_Fuse(myBody, myNeck);
        // Body : Create a Hollowed Solid 
        TopoDS_Face faceToRemove; 
        Standard_Real zMax = -1;
        for(TopExp_Explorer aFaceExplorer(myBody, TopAbs_FACE); aFaceExplorer.More(); aFaceExplorer.Next())
        { 
            TopoDS_Face aFace = TopoDS::Face(aFaceExplorer.Current()); // Check if <aFace> is the top face of the bottle’s neck 
            Handle(Geom_Surface) aSurface = BRep_Tool::Surface(aFace); 
            if(aSurface->DynamicType() == STANDARD_TYPE(Geom_Plane))
            { 
                Handle(Geom_Plane) aPlane = Handle(Geom_Plane)::DownCast(aSurface); 
                gp_Pnt aPnt = aPlane->Location(); 
                Standard_Real aZ = aPnt.Z(); 
                if(aZ > zMax)
                { 
                    zMax = aZ; 
                    faceToRemove = aFace; 
                }
            }
        }
        TopTools_ListOfShape facesToRemove; 
        facesToRemove.Append(faceToRemove); 
        BRepOffsetAPI_MakeThickSolid BodyMaker; 
        BodyMaker.MakeThickSolidByJoin(myBody, facesToRemove, -myThickness / 50, 1.e-3); 
        myBody = BodyMaker.Shape(); 
        // Threading : Create Surfaces 
        Handle(Geom_CylindricalSurface) aCyl1 = new Geom_CylindricalSurface(neckAx2, myNeckRadius * 0.99); 
        Handle(Geom_CylindricalSurface) aCyl2 = new Geom_CylindricalSurface(neckAx2, myNeckRadius * 1.05);
        // Threading : Define 2D Curves 
        gp_Pnt2d aPnt(2. * M_PI, myNeckHeight / 2.); 
        gp_Dir2d aDir(2. * M_PI, myNeckHeight / 4.); 
        gp_Ax2d anAx2d(aPnt, aDir);
        Standard_Real aMajor = 2. * M_PI; 
        Standard_Real aMinor = myNeckHeight / 10;
        Handle(Geom2d_Ellipse) anEllipse1 = new Geom2d_Ellipse(anAx2d, aMajor, aMinor); 
        Handle(Geom2d_Ellipse) anEllipse2 = new Geom2d_Ellipse(anAx2d, aMajor, aMinor / 4); 
        Handle(Geom2d_TrimmedCurve) anArc1 = new Geom2d_TrimmedCurve(anEllipse1, 0, M_PI); 
        Handle(Geom2d_TrimmedCurve) anArc2 = new Geom2d_TrimmedCurve(anEllipse2, 0, M_PI); 
        gp_Pnt2d anEllipsePnt1 = anEllipse1->Value(0); 
        gp_Pnt2d anEllipsePnt2 = anEllipse1->Value(M_PI);
        Handle(Geom2d_TrimmedCurve) aSegment = GCE2d_MakeSegment(anEllipsePnt1, anEllipsePnt2); 
        // Threading : Build Edges and Wires 
        TopoDS_Edge anEdge1OnSurf1 = BRepBuilderAPI_MakeEdge(anArc1, aCyl1); 
        TopoDS_Edge anEdge2OnSurf1 = BRepBuilderAPI_MakeEdge(aSegment, aCyl1); 
        TopoDS_Edge anEdge1OnSurf2 = BRepBuilderAPI_MakeEdge(anArc2, aCyl2); 
        TopoDS_Edge anEdge2OnSurf2 = BRepBuilderAPI_MakeEdge(aSegment, aCyl2); 
        TopoDS_Wire threadingWire1 = BRepBuilderAPI_MakeWire(anEdge1OnSurf1, anEdge2OnSurf1); 
        TopoDS_Wire threadingWire2 = BRepBuilderAPI_MakeWire(anEdge1OnSurf2, anEdge2OnSurf2); 
        BRepLib::BuildCurves3d(threadingWire1); 
        BRepLib::BuildCurves3d(threadingWire2);
        // Create Threading 
        BRepOffsetAPI_ThruSections aTool(Standard_True); 
        aTool.AddWire(threadingWire1); 
        aTool.AddWire(threadingWire2); 
        aTool.CheckCompatibility(Standard_False);
        TopoDS_Shape myThreading = aTool.Shape();
        // Building the Resulting Compound 
        TopoDS_Compound aRes; 
        BRep_Builder aBuilder; 
        aBuilder.MakeCompound (aRes); 
        aBuilder.Add (aRes, myBody); 
        aBuilder.Add (aRes, myThreading);
        return aRes;
    }

原文：https://blog.csdn.net/u012541187/article/details/81021064