OpenCasCade入门tutorial

其他 2018-07-18 19:00:26 阅读次数: 0

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。
——————————————————————————————
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;
}

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