Open CASCADE学习|BRepFill_SectionPlacement-编程知识

BRepFill_SectionPlacement 是一个与计算机辅助设计（CAD）相关的术语，通常用于指代一个几何对象或操作，它是Open CASCADE Technology（OCCT）中的一个类。Open CASCADE Technology是一个开源的CAD内核，广泛应用于工业软件中，用于处理3D模型的创建、编辑和数据交换。

在OCCT中，BRepFill_SectionPlacement 类的作用是将一个截面（或称为剖面）放置在特定的位置和方向上。这个类是用于填充操作的一部分，填充操作涉及创建一个3D实体，这个实体是通过将一个2D截面沿着一个路径或导线扫掠（sweep）形成的。

以下是关于 BRepFill_SectionPlacement 类的一些关键点：

截面（Section）：这是填充操作中的2D几何形状，可以是任何形状的轮廓，比如圆形、矩形或其他复杂形状。

放置（Placement）：这定义了截面在3D空间中的确切位置和方向。放置可以通过平移（translation）和旋转（rotation）来指定。

路径（Path）：在某些情况下，截面不是简单地放置在一个位置，而是沿着一个路径移动，从而创建一个更为复杂的3D形状。

生成实体（Generating Solids）：通过 BRepFill_SectionPlacement 可以生成3D实体，这些实体可以是实体的几何形状，如块、圆柱、管道等。

参数化（Parametric）：OCCT中的类通常是参数化的，这意味着它们的行为可以通过设置不同的参数来控制。

API（Application Programming Interface）：BRepFill_SectionPlacement 是OCCT提供的API的一部分，允许开发者在他们的应用程序中实现复杂的几何建模功能。

#include <BRepFill_LocationLaw.hxx>
#include <BRepFill_SectionPlacement.hxx>
#include <TopoDS_Shape.hxx>
#include <gp_Trsf.hxx>
#include <TColgp_HArray1OfPnt.hxx>
#include <Geom_CylindricalSurface.hxx>
#include <GeomAPI_PointsToBSpline.hxx>
#include <Geom_BSplineCurve.hxx>
#include <BRepBuilderAPI_MakeEdge.hxx>
#include <TopoDS_Edge.hxx>
#include <GC_MakeSegment.hxx>
#include <gp_Lin2d.hxx>
#include <GC_MakeArcOfCircle.hxx>
#include <IntAna2d_AnaIntersection.hxx>
#include <BRepBuilderAPI_MakeWire.hxx>
#include <BRepPrimAPI_MakeRevol.hxx>
#include <BRepBuilderAPI_Transform.hxx>
#include <GeomFill_TrihedronLaw.hxx>
#include <GeomFill_Frenet.hxx>
#include <GeomFill_CurveAndTrihedron.hxx>
#include <BRepFill_Edge3DLaw.hxx>
#include"Viewer.h"
TopoDS_Edge createHelix(const Standard_Real HelixRadius, const Standard_Real HelixAngle, const Standard_Real HelixLength)
{Standard_Real u0 = 0.0;Standard_Real u1 = 2 * M_PI;Standard_Real v0 = 0.0;Standard_Real v1 = HelixLength;double uInter = (u1 - u0) / 1000;double vInter = (v1 - v0) / 1000;TColgp_HArray1OfPnt Points(1, 1001);Handle(Geom_CylindricalSurface) aCylinder = new Geom_CylindricalSurface(gp::XOY(), HelixRadius);double u;double v;//生成点for (int i = 0; i < 1001; i++) {u = i * vInter * tan(HelixAngle) / HelixRadius;v = i * vInter;Points[i + 1] = aCylinder->Value(u, v);}GeomAPI_PointsToBSpline Approx(Points);Handle_Geom_BSplineCurve K = Approx.Curve();TopoDS_Edge aHelixEdge = BRepBuilderAPI_MakeEdge(K);return aHelixEdge;
}

TopoDS_Shape createGrindingwheel2()
{Standard_Real Line1_angle = 280 * M_PI / 180;Standard_Real Line1_length = 0.5031;Standard_Real Line2_angle = 236 * M_PI / 180;Standard_Real Line2_length = 0.5925;Standard_Real Arc1_r = 0.112;Standard_Real Arc1_angle = (180 + 10 + 50) * M_PI / 180;gp_Pnt Line1_p1(-0.6822 / 2, 0, 0);gp_Pnt Line2_p1(0.6822 / 2, 0, 0);gp_Lin Line1(Line1_p1, gp_Dir(cos(Line1_angle), sin(Line1_angle), 0.));gp_Lin Line2(Line2_p1, gp_Dir(cos(Line2_angle), sin(Line2_angle), 0.));Handle(Geom_TrimmedCurve) L1 = GC_MakeSegment(Line1, 0., Line1_length);TopoDS_Edge L1e = BRepBuilderAPI_MakeEdge(L1);Handle(Geom_TrimmedCurve) L2 = GC_MakeSegment(Line2, 0., Line2_length);TopoDS_Edge L2e = BRepBuilderAPI_MakeEdge(L2);gp_Pnt l1end = L1->EndPoint();gp_Pnt l2end = L2->EndPoint();gp_Lin Line1v(l1end, gp_Dir(cos(Line1_angle + M_PI_2), sin(Line1_angle + M_PI_2), 0.));gp_Lin2d Line2v(gp_Pnt2d(l2end.X(), l2end.Y()), gp_Dir2d(cos(Line2_angle - M_PI_2), sin(Line2_angle - M_PI_2)));gp_Lin Line2v3d(l2end, gp_Dir(cos(Line2_angle - M_PI_2), sin(Line2_angle - M_PI_2), 0.));Handle(Geom_TrimmedCurve) L1v = GC_MakeSegment(Line1v, 0., Arc1_r);gp_Pnt l1vend = L1v->EndPoint();gp_Circ c1(gp_Ax2(l1vend, gp_Dir(0, 0, 1)), Arc1_r);Handle(Geom_TrimmedCurve) c1c = GC_MakeArcOfCircle(c1, l1end, Arc1_angle, 1);gp_Pnt c1end = c1c->EndPoint();gp_Lin2d Line3(gp_Pnt2d(c1end.X(), c1end.Y()), gp_Dir2d(l2end.X() - c1end.X(), l2end.Y() - c1end.Y()));gp_Lin2d Line3v = Line3.Normal(gp_Pnt2d((l2end.X() + c1end.X()) / 2, (l2end.Y() + c1end.Y()) / 2));IntAna2d_AnaIntersection aIntAna;aIntAna.Perform(Line2v, Line3v);IntAna2d_IntPoint aIntPoint = aIntAna.Point(1);gp_Pnt o2(aIntPoint.Value().X(), aIntPoint.Value().Y(), 0.);Handle(Geom_TrimmedCurve) L2v = GC_MakeSegment(Line2v3d, l2end, o2);Standard_Real r2 = L2v->LastParameter();gp_Circ c2(gp_Ax2(o2, gp_Dir(0, 0, 1)), r2);Handle(Geom_TrimmedCurve) c2c = GC_MakeArcOfCircle(c2, c1end, l2end, 0);gp_Pnt c2low = c2c->Value(M_PI_2);
TopoDS_Edge c1ce = BRepBuilderAPI_MakeEdge(c1c);TopoDS_Edge L1ev = BRepBuilderAPI_MakeEdge(L1v);TopoDS_Edge c2ce = BRepBuilderAPI_MakeEdge(c2c);
gp_Pnt Line1_up(-0.9832 / 2, 5, 0);gp_Pnt Line2_up(0.9832 / 2, 5, 0);TopoDS_Edge anEdge1 = BRepBuilderAPI_MakeEdge(Line1_p1, Line1_up);TopoDS_Edge anEdge2 = BRepBuilderAPI_MakeEdge(Line1_up, Line2_up);TopoDS_Edge anEdge3 = BRepBuilderAPI_MakeEdge(Line2_up, Line2_p1);TopTools_ListOfShape listEdge;listEdge.Append(anEdge1);listEdge.Append(anEdge2);listEdge.Append(anEdge3);listEdge.Append(L1e);listEdge.Append(c1ce);listEdge.Append(c2ce);listEdge.Append(L2e);BRepBuilderAPI_MakeWire mw;mw.Add(listEdge);mw.Build();
TopoDS_Shape gwheel = BRepPrimAPI_MakeRevol(mw, gp_Ax1(gp_Pnt(0, 5, 0), gp_Dir(1, 0, 0)), 2 * M_PI);//平移：gp_Trsf theTransformation1;gp_Vec theVectorOfTranslation1(-c2low.X(), -c2low.Y(), 0.);theTransformation1.SetTranslation(theVectorOfTranslation1);
BRepBuilderAPI_Transform myBRepTransformation1(gwheel, theTransformation1);TopoDS_Shape outzero = myBRepTransformation1.Shape();

gp_Trsf theTransformation2;gp_Vec theVectorOfTranslation2(0., 0.525 / 2, 0.);theTransformation2.SetTranslation(theVectorOfTranslation2);//绕一个轴旋转：gp_Trsf theTransformation3;gp_Ax1 axez = gp_Ax1(gp_Pnt(0, 0, 0), gp_Dir(0., 0., 1.));theTransformation3.SetRotation(axez, -90 * M_PI / 180);
gp_Trsf theTransformation4;gp_Ax1 axex = gp_Ax1(gp_Pnt(0, 0, 0), gp_Dir(1., 0., 0.));theTransformation4.SetRotation(axex, -50 * M_PI / 180);
BRepBuilderAPI_Transform myBRepTransformation(outzero, theTransformation4 * theTransformation3 * theTransformation2);TopoDS_Shape TransformedShape = myBRepTransformation.Shape();
return TransformedShape;
}

int main() {// 假设已经有了一个截面形状 sectionShape 和一个路径定律 lawTopoDS_Shape sectionShape = createGrindingwheel2(); // 这里需要你填入实际的截面形状Standard_Real R = 0.306 / 2;TopoDS_Edge aE = createHelix(R, M_PI / 4, 6.);TopoDS_Wire spine = BRepBuilderAPI_MakeWire(aE);Handle(GeomFill_TrihedronLaw) TLaw;TLaw = new GeomFill_Frenet();Handle(GeomFill_CurveAndTrihedron) Loc = new (GeomFill_CurveAndTrihedron) (TLaw);Handle(BRepFill_LocationLaw) law; // 这里需要你填入实际的路径定律law = new (BRepFill_Edge3DLaw) (spine, Loc);// 创建 BRepFill_SectionPlacement 对象进行自动放置BRepFill_SectionPlacement placement(law, sectionShape, Standard_False, Standard_False);
// 获取放置操作产生的变换矩阵gp_Trsf transformation = placement.Transformation();
// 打印变换矩阵（或者进行其他操作）std::cout << "Transformation matrix:" << std::endl;for (Standard_Integer i = 1; i <= 3; ++i) {for (Standard_Integer j = 1; j <= 4; ++j) {std::cout << transformation.Value(i, j) << " ";}std::cout << std::endl;}
// 获取截面在路径上的曲线坐标Standard_Real abscissa = placement.AbscissaOnPath();std::cout << "Abscissa on path: " << abscissa << std::endl;TopoDS_Shape ch = BRepBuilderAPI_Transform(sectionShape, transformation, Standard_True);
Viewer vout(50, 50, 500, 500);vout << sectionShape;vout << spine;vout << ch;
vout.StartMessageLoop();return 0;
}

Transformation matrix:

-0.985547 -0.133209 0.104656 0.150789

0.167884 -0.685475 0.708476 -0.0256862

-0.0226364 0.715806 0.697932 0.00346336

Abscissa on path: 0