获得轮廓上距离鼠标最近的点

Handle(V3d_View) view3d = ...;

V3d_Coordinate XEye,YEye,ZEye,XAt,YAt,ZAt;
view3d->Eye(XEye,YEye,ZEye);
view3d->At(XAt,YAt,ZAt);
gp_Pnt EyePoint(XEye,YEye,ZEye);
gp_Pnt AtPoint(XAt,YAt,ZAt);
gp_Vec EyeVector(EyePoint,AtPoint);
gp_Dir EyeDir(EyeVector);

Standard_Real x, y, z;
view3d->Convert(scP.x, scP.y, x, y, z);
gp_Pnt tempPnt(x, y, z);

TopoDS_Wire sh = ...;

gp_Pnt aPnt;

  gp_Dir aDir;

pickNearestPoint(tempPnt,EyeDir, Sh, aPnt,aDir,TopAbs_EDGE);

Standard_Real DistanceOut(const TopoDS_Shape& S1, const TopoDS_Shape& S2)
{
Bnd_Box BBox1, BBox2;
BRepBndLib::Add(S1, BBox1);
BRepBndLib::Add(S2, BBox2);
return BBox1.Distance(BBox2);
}

Standard_Real DistanceIn(const TopoDS_Shape& S1, const TopoDS_Shape& S2)
{
Bnd_Box LBBox, SBBox;
BRepBndLib::Add(S1, SBBox);
BRepBndLib::Add(S2, LBBox);

Standard_Real LXmin, LYmin, LZmin, LXmax, LYmax, LZmax,
SXmin, SYmin, SZmin, SXmax, SYmax, SZmax;
SBBox.Get(SXmin, SYmin, SZmin,
SXmax, SYmax, SZmax);
LBBox.Get(LXmin, LYmin, LZmin,
LXmax, LYmax, LZmax);

//Compute the max distance between input shapes------------//
gp_XYZ Lmin(LXmin, LYmin, LZmin),
Lmax(LXmax, LYmax, LZmax);
gp_XYZ Smin(SXmin, SYmin, SZmin),
Smax(SXmax, SYmax, SZmax);
Lmax.Subtract(Lmin);
Smax.Subtract(Smin);
return Lmax.Modulus() + Smax.Modulus() + DistanceOut(S1, S2);
}

bool pickNearestPoint(const gp_Pnt& P, const gp_Dir& viewDir, const TopoDS_Shape &S, gp_Pnt& relPoint, gp_Dir& faceNormal,bool onlyEdges)
    {
        if (S.IsNull())
            return false;
        
        if (onlyEdges)
        {
            TopTools_IndexedMapOfShape M;
            TopExp::MapShapes(S, TopAbs_EDGE, M);
            int count = M.Extent();
            if (count == 0) return false;
            gp_Pnt tempProjPnt;
            gp_Dir tempProjPntFaceNormal;
            double maxDis = Precision::Infinite(), dis;
            bool isOk = false;
            for (int i = 1; i <= count; i++)
            {
                const TopoDS_Edge &E = TopoDS::Edge(M.FindKey(i));
                if (pickNearestPoint(P,viewDir,E, tempProjPnt, tempProjPntFaceNormal,false))
                {
                    dis = tempProjPnt.Distance(P);
                    if (dis < maxDis)
                    {
                        maxDis = dis;
                        relPoint = tempProjPnt;
                    }
                    isOk = true;
                }
            }
            return isOk;
        }
        else
        {
            double d = DistanceIn(BRepBuilderAPI_MakeVertex(P), S);
            gp_Vec Vsup(viewDir.XYZ() * 2 * d);


            TopoDS_Edge tempEdge = BRepBuilderAPI_MakeEdge(P.Translated(-1 * Vsup), P.Translated(Vsup)/*EyePoint*/);
            bool ok = false;
            //速度快
            if (S.ShapeType() == TopAbs_EDGE || S.ShapeType() == TopAbs_WIRE)
            {
                if (S.ShapeType() == TopAbs_EDGE)
                {
                    BRepExtrema_ExtCC ext(tempEdge, TopoDS::Edge(S));
                    if (ext.IsDone() && ext.NbExt() > 0)
                    {
                        //get min distance
                        double distance = Precision::Infinite();
                        for (int i = 1; i <= ext.NbExt(); i++)
                        {
                            Standard_Real d = ext.SquareDistance(i);
                            if (d < distance)
                            {
                                relPoint = ext.PointOnE2(i);
                                distance = d;
                                ok = true;
                            }
                        }
                    }
                }
            }
}
return true;
}

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