How to read complex entities (AP203)?

[Anton Shabalin]

Hello everyone! 

I have a STEP(AP203) file. And I don't know how to read complex entity (#97):

#140=ADVANCED_FACE('',(#184),#97,.T.);

#97=(

BOUNDED_SURFACE()

B_SPLINE_SURFACE(3,3,((#1023,#1024,#1025,#1026),(#1027,#1028,#1029,#1030),

(#1031,#1032,#1033,#1034),(#1035,#1036,#1037,#1038)),.UNSPECIFIED.,.F.,.F.,

 .F.)

B_SPLINE_SURFACE_WITH_KNOTS((4,4),(4,4),(0.,1.),(0.,1.),.UNSPECIFIED.)

GEOMETRIC_REPRESENTATION_ITEM()

RATIONAL_B_SPLINE_SURFACE(((1.,0.949253021674191,0.949253021674191,1.),(0.804737854124365,

0.763899839683158,0.763899839683158,0.804737854124365),(0.804737854124365,

0.763899839683158,0.763899839683158,0.804737854124365),(1.,0.949253021674191,

0.949253021674191,1.)))

REPRESENTATION_ITEM('')

SURFACE()

);

Ok. I have an Advanced_Face and can take face geometry:

SdaiAdvanced_face *adv_face = ...; //#140
SdaiSurface_ptr surfPtr = adv_face->face_geometry_();

Then I need to know what type of geometry it is:

std::string ent_name = surfPtr->eDesc->Name(); // I got "B_Spline_Surface"

And then when I try to cast it to SdaiB_spline_surface I got NULL:

SdaiB_spline_surface* b_spline_surf    = dynamic_cast<SdaiB_spline_surface *>(surfPtr);

So, the Question is: How to read this in a right way ?

[Mark]

Hi Anton,

I was going to suggest that the pointer could be null before the dynamic cast, but of course you wouldn't be able to read the eDesc if that was the case.

Complex instances can be difficult to work with, and I'm not sure exactly what's going on here.  Do you have an example (preferably small) that you can share via pastebin? If you can't share your code publicly, you could also email it directly to me.

BRL-CAD uses Advanced_Face ( http://sourceforge.net/p/brlcad/code/HEAD/tree/brlcad/trunk/src/conv/step/g-step/ON_Brep.cpp#l431 ) and B_spline_surface_with_knots (in ON_Brep.cpp and ON_NurbsSurface.cpp), but it looks like they are not doing the same thing that you are doing.

Regards

Mark

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[Anton Shabalin]

Hi Mark, 

The pointer is not null. I attached the step-file I want to parse. So have a look at instance #140. It has an SdaiAdvanced_Face type.

I can read complex entities just as in the example below:

#include "stdafx.h"
#include <string>
#include <STEPfile.h>
#include <STEPComplex.h>
#include <SdaiCONFIG_CONTROL_DESIGN.h>

int _tmain(int argc, _TCHAR* argv[])
{

    InstMgr *instance_list;
    Registry *registry;    
    STEPfile *sfile;

    instance_list = new InstMgr();
    registry = new Registry(SchemaInit);
    sfile = new STEPfile(*registry, *instance_list);

    std::string filename = "skrugl2.stp";
       
    if (sfile->ReadExchangeFile(filename)<SEVERITY_WARNING) {
        const ErrorDescriptor SCLError=sfile->Error();
        printf("%s\n",SCLError.UserMsg());
        printf("Details:(%s)\n",SCLError.DetailMsg());            
        return -1;
    }

//Find our entity

    auto Ent = instance_list->GetSTEPentity(140);

    SdaiAdvanced_face* adv_face = (SdaiAdvanced_face*)Ent;
    SdaiSurface_ptr surf_ptr =  (SdaiSurface_ptr)adv_face->face_geometry_();

    std::string ent_name = surf_ptr->eDesc->Name(); // I got "B_Spline_Surface"

    bool isComplex = (bool)surf_ptr->IsComplex();
    if (isComplex)
    {                            
          auto sc = ( ( STEPcomplex * )surf_ptr )->head;

          //Now I can parse all sub-entities...          
          while (sc)
          {
              sc->ResetAttributes();
              std::string sc_name = sc->eDesc->Name();
             
              if ( sc->IsA(config_control_design::e_b_spline_surface) )
              {
                  auto _instPtr = sc->eDesc->NewSTEPentity();
                 
                  //SdaiB_spline_surface* b_spl_surfPtr1 = (SdaiB_spline_surface*)sc->eDesc->NewSTEPentity();   //WRONG
                  //SdaiB_spline_surface* b_spl_surfPtr2 = (SdaiB_spline_surface*)sc;                           //WRONG
             }

              //... and all the attributes
              STEPattribute * attr;
              while (attr = sc->NextAttribute())
              {
                  std::string atrName = attr->aDesc->Name();
                  auto atrTypeName = attr->TypeName();

                  unsigned int u_degree = 0;

                  if (atrName=="u_degree")
                  {
                    u_degree = *attr->ptr.i;
                  }
              }
            sc = sc->sc;
          }      

        }
    delete instance_list;
    delete registry;
    delete sfile;

    return 0;
}

But if there is a less complicated method to read such entities ?

[Mark]

Hi Anton,

I believe you're doing it the best way. I want to simplify working with complex instances, but haven't had an opportunity to look into it yet. If you have suggestions, I'm interested in hearing them. If you had the inclination to create a patch, I'd also be interested in that ;)

Regards

Mark

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