如何获取TopoDS_Face的质心坐标？

Question

与 TopoDS_Vertex 一样，我们可以通过以下方式获取坐标：

int i=0;
exp0.Init(shape, TopAbs_VERTEX);
for(exp0.Init(shape, TopAbs_VERTEX); exp0.More(); exp0.Next()) {
    TopoDS_Vertex vertex = TopoDS::Vertex(exp0.Current());
    gp_Pnt pnt = BRep_Tool::Pnt(vertex);
    cout <<"Edge " << i << ": X: " << pnt.X() << " - Y:" << pnt.Y() << " - Z: " << pnt.Z();
    i++;
}

我想知道是否有类似的机制来获取TopoDS_Face的坐标。

编辑

根据@jaba的建议，我就是这样做来计算一系列点的质心的：

vtkSmartPointer<vtkPoints> facePoints = vtkSmartPointer<vtkPoints>::New();
int i=0;
for(exp0.Init(shape, TopAbs_FACE); exp0.More(); exp0.Next(), i++, count++) {
    facePoints->Reset();
    TopoDS_Face aFace = TopoDS::Face(exp0.Current());
    for (TopExp_Explorer Vex(aFace, TopAbs_VERTEX); Vex.More(); Vex.Next()) {
        TopoDS_Vertex vertex = TopoDS::Vertex(Vex.Current());
        gp_Pnt pnt = BRep_Tool::Pnt(vertex);
        facePoints->InsertNextPoint(p);
    }
    vtkSmartPointer<vtkPolyData> polydata = vtkSmartPointer<vtkPolyData>::New();
    polydata->SetPoints(facePoints);

    // Compute the center of mass
    vtkSmartPointer<vtkCenterOfMass> centerOfMassFilter = vtkSmartPointer<vtkCenterOfMass>::New();
    centerOfMassFilter->SetInputData(polydata);
    centerOfMassFilter->SetUseScalarsAsWeights(false);
    centerOfMassFilter->Update();
    double center[3];
    centerOfMassFilter->GetCenter(center);
}

Answer 1

你需要从面上获取一个顶点，因为一张面没有一个坐标。你所做的看起来很好，我只是添加了我的代码片段，因为你的代码不是独立的。

for (TopExp_Explorer vertexEx(face, TopAbs_VERTEX); vertexEx.More(); vertexEx.Next())
{
    TopoDS_Vertex vertex = TopoDS::Vertex(vertexEx.Current());
    gp_Pnt currentPnt = BRep_Tool::Pnt(vertex);
}

如果您只需要一个位置，您可以根据收到的顶点计算中心（参见 Compute the Centroid of a 3D Planar Polygon）

如果这不是您想要的，请说明您的问题。

Answer 2

计算 TopoDS_Face 质心的 Open CASCADE 方法是

TopoDS_Face face = ...;

GProp_GProps shellProps;
BRepGProp::SurfaceProperties(face, shellProps);

if (shellProps.Mass() < Precision::Confusion())
{
    throw Exception("Failed to Calculate the area of the face.", __TRACE__);
}

const gp_Pnt centerOfMass = shellProps.CentreOfMass();

这应该会给出正确的结果。如果面不受凸多边形的约束，其中面的顶点是多边形点，此代码应该仍然有效，但多边形方法可能会失败。

如何获取TopoDS_Face的质心坐标？

How to get the coordinates of the center of mass of a TopoDS_Face?

c++

vtk

opencascade