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Open cascade中如何使用BRepAlgoAPI_Splitter分割一个Face

news 2025/9/15 12:49:28

理论介绍

在OpenCASCADE几何建模内核中，BRepAlgoAPI_Splitter是一个强大的工具，用于将一个形状（Shape）用另一个形状（Tool）进行分割。这种操作在CAD建模中非常常见，比如用平面切割实体、用曲线分割曲面等。

BRepAlgoAPI_Splitter的工作原理是基于布尔运算的切割算法。它能够处理各种拓扑形状之间的分割操作，包括：

用边分割面
用面分割体
用线分割边

分割操作的结果取决于输入形状和工具的几何关系。当工具完全穿过被分割形状时，通常会产生多个子形状；当工具只部分接触时，则可能只修改原有形状而不分割。

核心代码分析

1. 创建被分割的面

TopoDS_Face makeFace(){gp_Pnt P1(-1.0/2.0, -1.0/2.0, 0);gp_Pnt P2(-1.0/2.0, 1.0/2.0, 0);gp_Pnt P3(1.0/2.0, 1.0/2.0, 0);gp_Pnt P4(极1.0/2.0, -1.0/2.0, 0);BRepBuilderAPI_MakePolygon mkPoly(P1,P2,P3,P4);mkPoly.Add(mkPoly.FirstVertex());TopoDS_Wire wire = mkPoly.Wire();BRepBuilderAPI_MakeFace face(wire);return face.Face();
}

这个函数创建一个正方形面，位于XY平面，边长1个单位，中心在原点。我们使用BRepBuilderAPI_MakePolygon创建多边形，然后将其闭合为Wire，最后用Wire创建Face。

2. 创建分割工具

TopoDS_Face makeTool(){static constexpr double bigNumber {100};gp_Pnt P1(0, -bigNumber, -bigNumber);gp_Pnt P极2(0, -bigNumber, bigNumber);gp_Pnt P3(0, bigNumber, bigNumber);gp_Pnt P4(0, bigNumber, -bigNumber);BRepBuilderAPI_MakePoly极gon mkPoly(P1,P2,P3,P4);mkPoly.Add(mkPoly.FirstVertex());TopoDS_Wire wire = mkPoly.Wire();BRepBuilderAPI_MakeFace tool(wire);return tool.Face();}

这里创建一个无限大的YZ平面（实际用大数100近似），作为分割工具。这个平面将垂直于X轴，穿过原点。

3. 执行分割操作

TopoDS_Face face = makeFace();TopoDS_Face tool = makeTool();TopTools_ListOfShape originalArguments;originalArguments.Append (face);TopTools_ListOfShape firstSplitLine;firstSplitLine.Append(tool);auto squareSplitOnce = BRepAlgoAPI_Splitter();squareSplitOnce.SetArguments(originalArguments);squareSplitOnce.SetTools(firstSplitLine);squareSplitOnce.Build();

关键步骤：

创建被分割的面和分割工具
将面添加到参数列表（Arguments）
将工具添加到工具列表（Tools）
创建BRepAlgoAPI_Splitter对象并设置参数和工具
调用Build()方法执行分割

4. 分析结果

Handle(BRepTools_History) hist = squareSplitOnce.History();hist->Dump(std::cout);auto generated = squareSplitOnce.Generated(face);std::cout << "generated: " << generated.Size() << '\n';auto modified = squareSplitOnce.Modified(face);std::cout << "modified: " << modified.Size() << '\n';

History()方法返回操作的历史记录，可以查询哪些形状被修改、生成或移除。Generated()和Modified()方法分别返回由输入形状生成的新形状和被修改的形状。

完整代码

#include <BRepBuilderAPI_MakeFace.hxx>
#include <BRepBuilderAPI_MakePolygon.hxx>
#include <BRepAlgoAPI_Splitter.hxx>
#include <TopoDS.hxx>
#include <TopoDS_Face.hxx>
#include <TopoDS_Wire.hxx>
#include <TopoDS_Iterator.hxx>
#include <TopExp_Explorer.hxx>
#include <TopTools_IndexedMapOfShape.hxx>
#include <iostream>TopoDS_Face makeFace()
{gp_Pnt P1(-1.0/2.0, -1.0/2.0, 0);gp_Pnt P2(-1.0/2.0, 1.0/2.0, 0);gp_Pnt P3(1.0/2.0, 1.0/2.0, 0);gp_Pnt P4(1.0/2.0, -1.0/2.0, 0);BRepBuilderAPI_MakePolygon mkPoly(P1,P2,P3,P4);mkPoly.Add(mkPoly.FirstVertex());TopoDS_Wire wire = mkPoly.Wire();BRepBuilderAPI_MakeFace face(wire);return face.Face();
}TopoDS_Face makeTool()
{static constexpr double bigNumber {100};gp_Pnt P1(0, -bigNumber, -bigNumber);gp_Pnt P2(0, -bigNumber, bigNumber);gp_Pnt P3(0, bigNumber, bigNumber);gp_Pnt P4(0, bigNumber, -bigNumber);BRepBuilderAPI_MakePolygon mkPoly(P1,P2,P3,P4);mkPoly.Add(mkPoly.FirstVertex());TopoDS_Wire wire = mkPoly.Wire();BRepBuilderAPI_MakeFace tool(wire);return tool.Face();
}void CountSubShape(const TopoDS_Face& face)
{TopTools_IndexedMapOfShape faces;TopTools_IndexedMapOfShape wires;TopTools_IndexedMapOfShape edges;TopTools_IndexedMapOfShape vertexes;for (TopExp_Explorer it(face, TopAbs_FACE); it.More(); it.Next()) {faces.Add(it.Current());}for (TopExp_Explorer it(face, TopAbs_WIRE); it.More(); it.Next()) {wires.Add(it.Current());}for (TopExp_Explorer it(face, TopAbs_EDGE); it.More(); it.Next()) {edges.Add(it.Current());}for (TopExp_Explorer it(face, TopAbs_VERTEX); it.More(); it.Next()) {vertexes.Add(it.Current());}std::cout << " faces=" << faces.Size()<< " wires=" << wires.Size()<< " edges=" << edges.Size()<< " vertexes=" << vertexes.Size()<< '\n';
}void PrintHistory(const TopTools_IndexedMapOfShape& map, Handle(BRepTools_History) hist)
{for (Standard_Integer i = 1; i <= map.Extent(); i++) {const TopoDS_Shape& shape = map(i);std::cout << "    modified: " << hist->Modified(shape).Size() << '\n';std::cout << "    generated: " << hist->Generated(shape).Size() << '\n';std::cout << "    removed: " << hist->IsRemoved(shape) << '\n';}
}void PrintHistory(const TopoDS_Face& face, Handle(BRepTools_History) hist)
{TopTools_IndexedMapOfShape faces;TopTools_IndexedMapOfShape wires;TopTools_IndexedMapOfShape edges;TopTools_IndexedMapOfShape vertexes;for (TopExp_Explorer it(face, TopAbs_FACE); it.More(); it.Next()) {faces.Add(it.Current());}for (TopExp_Explorer it(face, TopAbs_WIRE); it.More(); it.Next()) {wires.Add(it.Current());}for (TopExp_Explorer it(face, TopAbs_EDGE); it.More(); it.Next()) {edges.Add(it.Current());}for (TopExp_Explorer it(face, TopAbs_VERTEX); it.More(); it.Next()) {vertexes.Add(it.Current());}std::cout << "  faces:\n";PrintHistory(faces, hist);std::cout << "  wires:\n";PrintHistory(wires, hist);std::cout << "  edges:\n";PrintHistory(edges, hist);std::cout << "  vertexes:\n";PrintHistory(vertexes, hist);
}int main()
{TopoDS_Face face = makeFace();//CountSubShape(face);TopoDS_Face tool = makeTool();//CountSubShape(tool);TopTools_ListOfShape originalArguments;originalArguments.Append (face);TopTools_ListOfShape firstSplitLine;firstSplitLine.Append(tool);auto squareSplitOnce = BRepAlgoAPI_Splitter();squareSplitOnce.SetArguments(originalArguments);squareSplitOnce.SetTools(firstSplitLine);squareSplitOnce.Build();Handle(BRepTools_History) hist = squareSplitOnce.History();hist->Dump(std::cout);auto generated = squareSplitOnce.Generated(face);std::cout << "generated: " << generated.Size() << '\n';auto modified = squareSplitOnce.Modified(face);std::cout << "modified: " << modified.Size() << '\n';
#if 0std::cout << "\nface:\n";PrintHistory(face, hist);std::cout << "\ntool:\n";PrintHistory(tool, hist);
#endif
}