OpenCascade笔记：TopoDS_Shape数据结构的访问

以box为例

BRepPrimAPI_MakeBox mkBox(10, 10, 10);
TopoDS_Shape aShape = mkBox.Shape();

TopoDS_Shape数据结构

参看：OpenCascade笔记：【OpenCascade拓扑对象之：TopoDS_Shape的三要素】

TopoDS_Shape的HashCode

以下俩成员，作为生成hashCode的主要元素

• Handle(TopoDS_TShape) myTShape;
• TopLoc_Location myLocation;

方向成员TopAbs_Orientation myOrient;不参与HashCode的生成。

访问顶点

第一种遍历方式拿到的是体构建的TopoDS_Face、TopoDS_Edge、TopoDS_Vertex的数量；
第二种遍历方式拿到的是体构建的BRep_TFace、BRep_TEdge、BRep_TVertex的数量（最终展现形式还是TopoDS_Face、TopoDS_Edge、TopoDS_Vertex）。 举个例子：以BOX为例 TopExp_Explorer 遍历出48个顶点、24条边、6片面； TopExp遍历出8个顶点、12条边、6片面

	//第一种遍历方式拿到的是体构建的TopoDS_Face、TopoDS_Edge、TopoDS_Vertex的数量；
	//第二种遍历方式拿到的是体构建的BRep_TFace、BRep_TEdge、BRep_TVertex的数量（最终展现形式还是TopoDS_Face、TopoDS_Edge、TopoDS_Vertex）。
	//举个例子：以BOX为例
	//TopExp_Explorer 遍历出48个顶点、24条边、6片面；
	//TopExp遍历出8个顶点、12条边、6片面；


	//第一种遍历方式
	TopExp_Explorer aExp;
	int i = 1;
	for (aExp.Init(aShape, TopAbs_VERTEX); aExp.More(); aExp.Next(), ++i )
	{
		const TopoDS_Vertex& aVertex = TopoDS::Vertex(aExp.Current());
		gp_Pnt aPnt = BRep_Tool::Pnt(aVertex);

		std::cout << "vertex " << i << ": (" << aPnt.X() << ", " << aPnt.Y()
			<< ", " << aPnt.Z() << "), vertex's hash code is " 
			<< aVertex.HashCode(INT_MAX) << std::endl;
	}

	//第二种遍历方式
	TopTools_IndexedMapOfShape aVertexMap;
	TopExp::MapShapes(aShape, TopAbs_VERTEX, aVertexMap);
	cout << "vertex count is " << aVertexMap.Extent() << std::endl;
	for (int i = 1; i <= aVertexMap.Extent(); ++i)
	{
		const TopoDS_Vertex& aVertex = TopoDS::Vertex(aVertexMap(i));
		gp_Pnt aPnt = BRep_Tool::Pnt(aVertex);

		std::cout << "vertex " << i << ": (" << aPnt.X() << ", " << aPnt.Y()
			<< ", " << aPnt.Z() << "), vertex's hash code is "
			<< aVertex.HashCode(INT_MAX) << std::endl;
	}

访问边

	//第一种遍历方式拿到的是体构建的TopoDS_Face、TopoDS_Edge、TopoDS_Vertex的数量；
	//第二种遍历方式拿到的是体构建的BRep_TFace、BRep_TEdge、BRep_TVertex的数量（最终展现形式还是TopoDS_Face、TopoDS_Edge、TopoDS_Vertex）。
	//举个例子：以BOX为例
	//TopExp_Explorer 遍历出48个顶点、24条边、6片面；
	//TopExp遍历出8个顶点、12条边、6片面；


	//第一种遍历方式
	TopExp_Explorer aExp;
	int i = 1;
	for (aExp.Init(aShape, TopAbs_EDGE); aExp.More(); aExp.Next(), ++i )
	{
		const TopoDS_Edge& aEdge = TopoDS::Edge(aExp.Current());
		const TopoDS_Vertex& aFirstVertex = TopExp::FirstVertex(aEdge);
		const TopoDS_Vertex& aLastVertex = TopExp::LastVertex(aEdge);
	}

	//第二种遍历方式
	TopTools_IndexedMapOfShape aEdgeMap;
	TopExp::MapShapes(aShape, TopAbs_EDGE, aEdgeMap);
	cout << "edge count is " << aEdgeMap.Extent() << std::endl;
	for (int i = 1; i <= aEdgeMap.Extent(); ++i)
	{
		const TopoDS_Edge& aEdge = TopoDS::Edge(aEdgeMap(i));
		const TopoDS_Vertex& aFirstVertex = TopExp::FirstVertex(aEdge);
		const TopoDS_Vertex& aLastVertex = TopExp::LastVertex(aEdge);

		Standard_Real fBegin = 0, fEnd = 0;
		Handle(Geom_Curve) hCurve = BRep_Tool::Curve(aEdge, fBegin, fEnd);
		if (!hCurve.IsNull()) 
		{
			//边是条几何线，如直线、椭圆线、贝塞尔曲线等等

			//散列化，进行取点
			float fLen = float(fEnd - fBegin);
			int ulNbOfPoints = 30;
			for (int i = 0; i < ulNbOfPoints; i++)
			{
				const gp_Pnt& ptPoint = hCurve->Value(fBegin + (fLen * float(i)) / float(ulNbOfPoints - 1));
				
			}

			continue;
		}



		TopLoc_Location locPolygon;
		Handle(Poly_Polygon3D) hPolygon3D = BRep_Tool::Polygon3D(aEdge, locPolygon);
		if (!hPolygon3D.IsNull())
		{
			//边是条多段线（曲线的近似表示）
			Standard_Integer nNodeCount = hPolygon3D->NbNodes();
			const TColgp_Array1OfPnt& mNodes = hPolygon3D->Nodes();
			for (int i = 1; i <= nNodeCount; ++i)
			{
				const gp_Pnt& ptPoint = mNodes(i);
			}
		}

	}

附上occ中几何曲线的类层次

面的访问

	//拆分三角形
	Bnd_Box bounds;
	BRepBndLib::Add(aShape, bounds);
	bounds.SetGap(0.0);
	Standard_Real xMin, yMin, zMin, xMax, yMax, zMax;
	bounds.Get(xMin, yMin, zMin, xMax, yMax, zMax);
	Standard_Real deflection = ((xMax - xMin) + (yMax - yMin) + (zMax - zMin)) / 300.0 *0.5;
	BRepMesh_IncrementalMesh(aShape, deflection, false);


	//第一种遍历方式拿到的是体构建的TopoDS_Face、TopoDS_Edge、TopoDS_Vertex的数量；
	//第二种遍历方式拿到的是体构建的BRep_TFace、BRep_TEdge、BRep_TVertex的数量（最终展现形式还是TopoDS_Face、TopoDS_Edge、TopoDS_Vertex）。
	//举个例子：以BOX为例
	//TopExp_Explorer 遍历出48个顶点、24条边、6片面；
	//TopExp遍历出8个顶点、12条边、6片面；


	//第一种遍历方式
	TopExp_Explorer aExp;
	int i = 1;
	for (aExp.Init(aShape, TopAbs_FACE); aExp.More(); aExp.Next(), ++i )
	{
		const TopoDS_Edge& aEdge = TopoDS::Edge(aExp.Current());
		const TopoDS_Vertex& aFirstVertex = TopExp::FirstVertex(aEdge);
		const TopoDS_Vertex& aLastVertex = TopExp::LastVertex(aEdge);
	}

	//第二种遍历方式
	TopTools_IndexedMapOfShape aFaceMap;
	TopExp::MapShapes(aShape, TopAbs_FACE, aFaceMap);
	cout << "face count is " << aFaceMap.Extent() << std::endl;
	for (int i = 1; i <= aFaceMap.Extent(); ++i)
	{
		const TopoDS_Face& curFace = TopoDS::Face(aFaceMap(i));
		BRepAdaptor_Surface adaptorSurface(curFace);
		GeomAbs_SurfaceType surfaceType = adaptorSurface.GetType();
		//GeomAbs_Plane,
		//GeomAbs_Cylinder,
		//GeomAbs_Cone,
		//GeomAbs_Sphere,
		//GeomAbs_Torus,
		//GeomAbs_BezierSurface,
		//GeomAbs_BSplineSurface,
		//GeomAbs_SurfaceOfRevolution,
		//GeomAbs_SurfaceOfExtrusion,
		//GeomAbs_OffsetSurface,
		//GeomAbs_OtherSurface

		//前面对面进行了三角化（BRepMesh_IncrementalMesh）
		//此处可以取出三角面信息
		TopLoc_Location aLoc;
		Handle(Poly_Triangulation) mesh = BRep_Tool::Triangulation(
			curFace, aLoc);
		if (mesh.IsNull())
		{
			continue;
		}

		const Poly_Array1OfTriangle& mTriangles = mesh->Triangles();
		const TColgp_Array1OfPnt& mNodes = mesh->Nodes();
		for (int g = 1; g <= mesh->NbTriangles(); g++)
		{
			// Get the triangle
			Standard_Integer N1, N2, N3;
			mTriangles(g).Get(N1, N2, N3);

			// change orientation of the triangles
			if (curFace.Orientation() != TopAbs_FORWARD) {
				Standard_Integer tmp = N1;
				N1 = N2;
				N2 = tmp;
			}

			gp_Pnt V1 = mNodes(N1);
			gp_Pnt V2 = mNodes(N2);
			gp_Pnt V3 = mNodes(N3);

			if (!aLoc.IsIdentity())
			{
				V1.Transform(aLoc.Transformation());
				V2.Transform(aLoc.Transformation());
				V3.Transform(aLoc.Transformation());
			}
		}

		//.....

	}

附上occ中几何面的类层次

Wire、Shell、Solid的访问

与上文类似

参看

https://blog.csdn.net/Mengxy_2021/article/details/117732021