how to verify 2 faces share one same edge - Forum Open Cascade Technology

Boqing Dong
Sat, 12/16/2023 - 04:19

Forums:

For any 2 faces that join at one edge, I usually iterate each edge edge1 from face 1 and edge2 from face 2, and then make a comparison by using the below code:
edge1.TShape() == edge2.TShape()
or
edge1.IsPartner(edge2)

It doesn't work as expected always, as sometimes the edges' TShape do differ, even though they're actually the same in the model, I mean, they have the same curve type and start/end points.

Is there a better way to verify it?

Thanks.

Boqing Dong
Sat, 12/16/2023 - 04:24

I tried to dump the json data of the 2 edges in question if it's goanna help:

The json data here:

Edge1:
"className": "BRep_TEdge"
"className": "TopoDS_TShape"
"this": "0x2137B5F97F0"
"ShapeType": 6
"NbChildren": 2
"Flags": 10
"Free": 0
"Free": 0
"Locked": 0
"Modified": 1
"Checked": 0
"Orientable": 1
"Closed": 0
"Infinite": 0
"Convex": 0
"Tolerance": 1e-07
"Flags": 3
"CurveRepresentation":
{
"className": "BRep_Curve3D", "className": "BRep_GCurve", "className": "BRep_CurveRepresentation", "Location": {"className": "TopLoc_Location", "Transformation": {"Location": [0, 0, 0], "Matrix": [1, 0, 0, 0, 1, 0, 0, 0, 1], "shape": 0, "scale": 1}, "IsIdentity": 1}, "First": 0, "Last": 10, "Curve": {"className": "Geom_BSplineCurve", "className": "Geom_BoundedCurve", "className": "Geom_Curve", "className": "Geom_Geometry", "rational": 0, "periodic": 0, "knotSet": 3, "smooth": 6, "deg": 1, "poles->Size": 2, "flatknots->Size": 4, "knots->Size": 2, "mults->Size": 2, "maxderivinv": 0, "maxderivinvok": 0}}
"CurveRepresentation":
{
"className": "BRep_CurveOnSurface", "className": "BRep_GCurve", "className": "BRep_CurveRepresentation", "Location": {"className": "TopLoc_Location", "Transformation": {"Location": [0, 0, 0], "Matrix": [1, 0, 0, 0, 1, 0, 0, 0, 1], "shape": 0, "scale": 1}, "IsIdentity": 1}, "First": 0, "Last": 10, "UV1": {"gp_Pnt2d": [0, 10]}, "UV2": {"gp_Pnt2d": [10, 10]}, "PCurve": {"className": "Geom2d_Line", "className": "Geom2d_Curve", "className": "Geom2d_Geometry", "pos": {"className": "gp_Ax2d", "loc": {"gp_Pnt2d": [0, 10]}, "vdir": {"gp_Dir2d": [1, 0]}}}, "Surface": {"className": "Geom_BSplineSurface", "className": "Geom_Surface", "className": "Geom_Geometry", "urational": 0, "vrational": 0, "uperiodic": 0, "vperiodic": 0, "uknotSet": 3, "vknotSet": 3, "Usmooth": 6, "Vsmooth": 6, "udeg": 1, "vdeg": 1, "poles->Size": 4, "weights->Size": 4, "ufknots->Size": 4, "vfknots->Size": 4, "uknots->Size": 2, "vknots->Size": 2, "umults->Size": 2, "vmults->Size": 2, "umaxderivinv": 0.707107, "vmaxderivinv": 0.707107, "maxderivinvok": 1}}
===============================================================================================

Edge2:
"className": "BRep_TEdge"
"className": "TopoDS_TShape"
"this": "0x2137B5F9F70"
"ShapeType": 6
"NbChildren": 2
"Flags": 10
"Free": 0
"Free": 0
"Locked": 0
"Modified": 1
"Checked": 0
"Orientable": 1
"Closed": 0
"Infinite": 0
"Convex": 0
"Tolerance": 1e-07
"Flags": 3
"CurveRepresentation":
{
"className": "BRep_Curve3D", "className": "BRep_GCurve", "className": "BRep_CurveRepresentation", "Location": {"className": "TopLoc_Location", "Transformation": {"Location": [0, 0, 0], "Matrix": [1, 0, 0, 0, 1, 0, 0, 0, 1], "shape": 0, "scale": 1}, "IsIdentity": 1}, "First": 20, "Last": 30, "Curve": {"className": "Geom_BSplineCurve", "className": "Geom_BoundedCurve", "className": "Geom_Curve", "className": "Geom_Geometry", "rational": 0, "periodic": 0, "knotSet": 3, "smooth": 6, "deg": 1, "poles->Size": 2, "flatknots->Size": 4, "knots->Size": 2, "mults->Size": 2, "maxderivinv": 0, "maxderivinvok": 0}}
"CurveRepresentation":
{
"className": "BRep_CurveOnSurface", "className": "BRep_GCurve", "className": "BRep_CurveRepresentation", "Location": {"className": "TopLoc_Location", "Transformation": {"Location": [0, 0, 0], "Matrix": [1, 0, 0, 0, 1, 0, 0, 0, 1], "shape": 0, "scale": 1}, "IsIdentity": 1}, "First": 20, "Last": 30, "UV1": {"gp_Pnt2d": [20, 10]}, "UV2": {"gp_Pnt2d": [30, 10]}, "PCurve": {"className": "Geom2d_Line", "className": "Geom2d_Curve", "className": "Geom2d_Geometry", "pos": {"className": "gp_Ax2d", "loc": {"gp_Pnt2d": [0, 10]}, "vdir": {"gp_Dir2d": [1, 0]}}}, "Surface": {"className": "Geom_BSplineSurface", "className": "Geom_Surface", "className": "Geom_Geometry", "urational": 0, "vrational": 0, "uperiodic": 0, "vperiodic": 0, "uknotSet": 3, "vknotSet": 3, "Usmooth": 6, "Vsmooth": 6, "udeg": 1, "vdeg": 1, "poles->Size": 4, "weights->Size": 4, "ufknots->Size": 4, "vfknots->Size": 4, "uknots->Size": 2, "vknots->Size": 2, "umults->Size": 2, "vmults->Size": 2, "umaxderivinv": 0.707107, "vmaxderivinv": 0.707107, "maxderivinvok": 1}}

Dmitrii Pasukhin
Sun, 12/17/2023 - 15:11

Hello, in this case it is not possible to easy equal. The pointers are different. As a solution, you can additionally compare Handle of own curve. If the the same, it can helps. But if it is not. You will need to make deep comparison. Unfortunately, I don't know the prepared functions for that.

Best regards,Dmitrii.

Boqing Dong
Mon, 12/18/2023 - 05:22

Dear Dmitrii,

Thank you very much for the elaboration.

You mentioned the comparison of curve handles. Can you give me a quick example of how to do it?

Best regards, Boqing

Dmitrii Pasukhin
Mon, 12/18/2023 - 13:37

TopoDS_Edge anOrigin, aNewEdge;
TopLoc_Location aDummyLoc;
Standard_Real aDummyEnd, aDummyStart;
cons auto anOrigCurve = BRep_Tool::Curve(anOrigin, aDummyLoc, aDummyStart, aDummyEnd);
cons auto anNewCurve = BRep_Tool::Curve(aNewEdge, aDummyLoc, aDummyStart, aDummyEnd);
return anOrigCurve == anNewCurve;