如何获取TopoDS_Face的质心坐标？

Question

和TopoDS_Vertex一样，我们可以得到坐标：

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，这就是我用来计算一系列点的质心的方法：

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

Open CASCADE计算TopoDS_Face质心的方法是

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，则此代码仍然可以工作，但多边形方法可能会失败。

Answer 2

您需要从面部获取顶点，因为面没有一个坐标。你做的看起来很好，我刚刚添加了我的代码片段，因为你的代码不是自包含的。

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);
}

如果你只想要一个位置，你可以从你收到的顶点计算中心（见Compute the Centroid of a 3D Planar Polygon）

如果这不是您想要的，请指出您的问题。