minimum distance between two curves - Forum Open Cascade Technology

Aziz GH
Thu, 12/08/2022 - 14:04

Forums:

Hello together,
how can I use OCC to calculate the minimum distance between two curves, as in the picture?
GeomAPI_ExtremaCurveCurve calculates the distance between Extremas.

Attachments:

min-distance(1).png

Mikhail Sazonov
Thu, 12/08/2022 - 15:22

GeomAPI_ExtremaCurveCurve first calculates all minimal distances using Extrema_ExtCC, and optionally you can request solutions using the end points.

If the algorithm does not calculate expected solution you are welcome to create a bug.

Aziz GH
Sat, 12/10/2022 - 14:35

Thank you for your answer.

I have tested this function with the following data. The result is shown below.
For the two cases you don't get a distance between the lines, why?

Handle(Geom_TrimmedCurve) line1 = GC_MakeSegment(gp_Pnt(0, 0, 0), gp_Pnt(10, 0, 0));
Handle(Geom_TrimmedCurve) line2 = GC_MakeSegment(gp_Pnt(0, 10, 0), gp_Pnt(10, 10, 0));
Handle(Geom_TrimmedCurve) line3 = GC_MakeSegment(gp_Pnt(10, 10, 0), gp_Pnt(10, 0, 0));
Handle(Geom_TrimmedCurve) line4 = GC_MakeSegment(gp_Pnt(10, 20, 0), gp_Pnt(10, 10, 0));
Handle(Geom_TrimmedCurve) line5 = GC_MakeSegment(gp_Pnt(0, 10, 0), gp_Pnt(20, 0, 0));

GeomAPI_ExtremaCurveCurve extrema1(line1, line2);
GeomAPI_ExtremaCurveCurve extrema2(line1, line3);
GeomAPI_ExtremaCurveCurve extrema3(line1, line4);
GeomAPI_ExtremaCurveCurve extrema4(line1, line5);

qDebug() << "extream1:";
qDebug() << "nr: " << extrema1.NbExtrema();
if (extrema1.NbExtrema() > 0)
qDebug() << "lower distance: " << extrema1.LowerDistance();

qDebug() << "extream2:";
qDebug() << "nr: " << extrema2.NbExtrema();
if(extrema2.NbExtrema() > 0)
qDebug() << "lower distance: " << extrema2.LowerDistance();

qDebug() << "extream3:";
qDebug() << "nr: " << extrema3.NbExtrema();
if(extrema3.NbExtrema() > 0)
qDebug() << "lower distance: " << extrema3.LowerDistance();

qDebug() << "extream4:";
qDebug() << "nr: " << extrema4.NbExtrema();
if (extrema4.NbExtrema() > 0)
qDebug() << "lower distance: " << extrema4.LowerDistance();

output:

extream1:
nr: 1
lower distance: 10
extream2:
nr: 1
lower distance: 0
extream3:
nr: 0
extream4:
nr: 0

Mikhail Sazonov
Sat, 12/10/2022 - 23:34

NBExtrema returns only solutions where the distance vector is perpendicular to both curves.

Probably you need to request extended solution using the method TotalLowerDistance.

Aziz GH
Sun, 12/11/2022 - 12:10

Thank you, TotalLowerDistance is exactly what I need.
You really helped me a lot.

Mauro Mariotti
Wed, 11/15/2023 - 13:53

Thanks.
I used TotalLowerDistance but I found two trivial bugs:
1) square of RealLast(), with gave "inf" as result in my debugger, here
Standard_Real aTotalDist2 = myTotalDist * myTotalDist;
(line 390 in GeomAPI_ExtremaCurveCurve.cxx, version 7.7.0)
2) missing update of aTotalDist2 here
if(aTotalDist2 > d11) {
myTotalDist = sqrt (d11);
and in the three following "if" blocks (lines 392,403,414,425).

I attach my correction.
I can insert the bug if you tell me how to save two Geom_Curve's in a brep file. For shapes I use BRepTools::Write.

Regards.
Mauro

Attachments:

GeomAPI_ExtremaCurveCurve.cxx