How to read the units of a STEP file - Forum Open Cascade Technology

John Bijnens
Thu, 08/09/2018 - 21:34

Forums:

Can anyone point me into the right direction how to read the measurement units and the accuracy specified in a STEP file that is specified within the STEP that is generated with a CAD package like Creo?

#644=UNCERTAINTY_MEASURE_WITH_UNIT(LENGTH_MEASURE(1.E-2),#638,'closure',

#638=(LENGTH_UNIT()NAMED_UNIT(*)SI_UNIT(.MILLI.,.METRE.));

I've tried to do that with

const Handle(XSControl_WorkSession)& theSession = aReader.WS();
const Handle(Interface_InterfaceModel)& theModel = theSession->Model();

   Standard_Integer nb = theModel->NbEntities(); // Returns count of contained Entities.
   for (Standard_Integer i = 1; i <= nb; i++)
   {
       Handle(StepRepr_Representation) ent = Handle(StepRepr_Representation)::DownCast(theModel->Value(i));
       if (ent.IsNull())
           continue;
       if (ent->Name().IsNull())
           continue;
       printf("%s\n", ent->Name()->ToCString());
   }

Apparently this is not the correct way.
Any advice is much appreciated.

John Bijnens
Sat, 08/11/2018 - 23:21

I've tried to use the methode FileUnits*
I read however that this doesn't work when the STEP geometry is already converted to a BREP model in OCC.
So I tried
    Handle(StepData_StepModel) hModel = Handle(StepData_StepModel)::DownCast(aReader.Model());
   for (int i = 1; i <= hModel->NbEntities(); ++i)
   {
       if ((hModel->Entity(i))->IsKind(STANDARD_TYPE(StepBasic_ConversionBasedUnitAndLengthUnit)))
       {
           Handle(StepBasic_ConversionBasedUnitAndLengthUnit) convUnit = Handle(StepBasic_ConversionBasedUnitAndLengthUnit)::DownCast(hModel->Entity(i));
           TCollection_HAsciiString unitName = convUnit->Name();
           unitName.Print(cout);
           break;
       }
   }

The line if ((hModel->Entity(i))->IsKind(STANDARD_TYPE(StepBasic_ConversionBasedUnitAndLengthUnit)))

gives a false so this doesn't work either.

Any hint or advice is very much appreciated.