DAE cf WRL at code level

Compare G4DAE and VRML2 geometry handling code

1. comparing VRML2 and G4DAE code for vertices : looks identical,
   • maybe some parameters : dont think so, all seem at defaults
   • precision issue

Promising explanation but seemingly not the case

DAE creation so far uses expedient of running from a Geant4 geometry created from an exported GDML file, for development speed. BUT that compounds precision issues. The polyhedron creation algorithm appears sensitive to precise geometry especially when you have subtraction/union solids. Checked this by testing DAE creation direct from original in memory model, not the one loaded from the GDML. This allows to compare apples-to-apples rather than comparison against 2nd generation geometry filtered thru GDML precision.

The results of that comparison are precisely the same, perhaps some parameter tweaks in VRML2 ?

BooleanProcessor

graphics_reps/src/BooleanProcessor.src

G4Polyhedron::SetNumberOfRotationSteps ?

Given that the differences are all in subtraction/union solids it seems unlikely to be a difference in such a parameter. To determine perhaps could add some extra metadata to the exported DAE with param values ?

[blyth@belle7 source]$ find . -exec grep -H G4Polyhedron:: {} \;
./visualization/modeling/src/G4PhysicalVolumeModel.cc:      G4Polyhedron::SetNumberOfRotationSteps
./visualization/modeling/src/G4PhysicalVolumeModel.cc:      G4Polyhedron::SetNumberOfRotationSteps(fpMP->GetNoOfSides());
./visualization/modeling/src/G4PhysicalVolumeModel.cc:    G4Polyhedron::ResetNumberOfRotationSteps();
./visualization/management/src/G4VSceneHandler.cc:    G4Polyhedron::SetNumberOfRotationSteps (GetNoOfSides (fpVisAttribs));
./visualization/management/src/G4VSceneHandler.cc:    G4Polyhedron::ResetNumberOfRotationSteps ();
./geometry/solids/specific/src/G4TwistedTubs.cc:    G4int(G4Polyhedron::GetNumberOfRotationSteps() * dA / twopi) + 2;
./geometry/solids/specific/src/G4TwistedTubs.cc:    G4int(G4Polyhedron::GetNumberOfRotationSteps() * fPhiTwist / twopi) + 2;
./geometry/solids/specific/src/G4VTwistedFaceted.cc:    G4int(G4Polyhedron::GetNumberOfRotationSteps() * fPhiTwist / twopi) + 2;
./geometry/solids/specific/src/G4Polycone.cc:          G4int(G4Polyhedron::GetNumberOfRotationSteps()
./geometry/solids/specific/History:  G4Polyhedron::GetNumberOfRotationSteps().
./graphics_reps/include/HepPolyhedron.h://    G4Polyhedron::SetNumberOfRotationSteps
./graphics_reps/include/HepPolyhedron.h://    G4Polyhedron::ResetNumberOfRotationSteps ();
./graphics_reps/src/G4Polyhedron.cc:G4Polyhedron::G4Polyhedron ():
./graphics_reps/src/G4Polyhedron.cc:G4Polyhedron::~G4Polyhedron () {}
./graphics_reps/src/G4Polyhedron.cc:G4Polyhedron::G4Polyhedron (const HepPolyhedron& from)
./graphics_reps/History:- Added G4Polyhedron::Transform and G4Polyhedron::InvertFacets (Evgeni
[blyth@belle7 source]$

graphics_reps/include/HepPolyhedron.h:

105 //   GetNumberOfRotationSteps()   - get number of steps for whole circle;
106 //   SetNumberOfRotationSteps (n) - set number of steps for whole circle;
107 //   ResetNumberOfRotationSteps() - reset number of steps for whole circle
108 //                            to default value;
109 //   IsErrorBooleanProcess()- true if there has been an error during the
110 //                            processing of a Boolean operation.
...
168 #ifndef HEP_POLYHEDRON_HH
169 #define HEP_POLYHEDRON_HH
170
171 #include <CLHEP/Geometry/Point3D.h>
172 #include <CLHEP/Geometry/Normal3D.h>
173
174 #ifndef DEFAULT_NUMBER_OF_STEPS
175 #define DEFAULT_NUMBER_OF_STEPS 24
176 #endif

LCG/geant4.9.2.p01/source/visualization/management/src/G4VSceneHandler.cc:

421 void G4VSceneHandler::RequestPrimitives (const G4VSolid& solid) {
422   BeginPrimitives (*fpObjectTransformation);
423   G4NURBS* pNURBS = 0;
424   G4Polyhedron* pPolyhedron = 0;
425   switch (fpViewer -> GetViewParameters () . GetRepStyle ()) {
426   case G4ViewParameters::nurbs:
427     pNURBS = solid.CreateNURBS ();
428     if (pNURBS) {
429       pNURBS -> SetVisAttributes (fpVisAttribs);
430       AddPrimitive (*pNURBS);
431       delete pNURBS;
432       break;
433     }
434     else {
435       G4VisManager::Verbosity verbosity =
436     G4VisManager::GetInstance()->GetVerbosity();
437       if (verbosity >= G4VisManager::errors) {
438     G4cout <<
439       "ERROR: G4VSceneHandler::RequestPrimitives"
440       "\n  NURBS not available for "
441            << solid.GetName () << G4endl;
442     G4cout << "Trying polyhedron." << G4endl;
443       }
444     }
445     // Dropping through to polyhedron...
446   case G4ViewParameters::polyhedron:
447   default:
448     G4Polyhedron::SetNumberOfRotationSteps (GetNoOfSides (fpVisAttribs));
449     pPolyhedron = solid.GetPolyhedron ();
450     G4Polyhedron::ResetNumberOfRotationSteps ();
451     if (pPolyhedron) {
452       pPolyhedron -> SetVisAttributes (fpVisAttribs);
453       AddPrimitive (*pPolyhedron);
454     }
455     else {
456       G4VisManager::Verbosity verbosity =
457     G4VisManager::GetInstance()->GetVerbosity();
458       if (verbosity >= G4VisManager::errors) {
459     G4cout <<
460       "ERROR: G4VSceneHandler::RequestPrimitives"
461       "\n  Polyhedron not available for " << solid.GetName () <<
462       ".\n  This means it cannot be visualized on most systems."
463       "\n  Contact the Visualization Coordinator." << G4endl;
464       }
465     }
466     break;
467   }
468   EndPrimitives ();
469 }

859 G4int G4VSceneHandler::GetNoOfSides(const G4VisAttributes* pVisAttribs)
860 {
861   // No. of sides (lines segments per circle) is normally determined
862   // by the view parameters, but it can be overriddden by the
863   // ForceLineSegmentsPerCircle in the vis attributes.
864   G4int lineSegmentsPerCircle = fpViewer->GetViewParameters().GetNoOfSides();
865   if (pVisAttribs) {
866     if (pVisAttribs->IsForceLineSegmentsPerCircle())
867       lineSegmentsPerCircle = pVisAttribs->GetForcedLineSegmentsPerCircle();
868     const G4int nSegmentsMin = 12;
869     if (lineSegmentsPerCircle < nSegmentsMin) {
870       lineSegmentsPerCircle = nSegmentsMin;
871       G4cout <<
872     "G4VSceneHandler::GetNoOfSides: attempt to set the"
873     "\nnumber of line segements per circle < " << nSegmentsMin
874          << "; forced to " << lineSegmentsPerCircle << G4endl;
875     }
876   }
877   return lineSegmentsPerCircle;
878 }

Geant4

geometry/solids/Boolean/src/G4UnionSolid.cc:

453 G4Polyhedron*
454 G4UnionSolid::CreatePolyhedron () const
455 {
456   G4Polyhedron* pA = fPtrSolidA->GetPolyhedron();
457   G4Polyhedron* pB = fPtrSolidB->GetPolyhedron();
458   if (pA && pB) {
459     G4Polyhedron* resultant = new G4Polyhedron (pA->add(*pB));
460     return resultant;
461   } else {
462     std::ostringstream oss;
463     oss << GetName() <<
464       ": one of the Boolean components has no corresponding polyhedron.";
465     G4Exception("G4UnionSolid::CreatePolyhedron",
466         "", JustWarning, oss.str().c_str());
467     return 0;
468   }
469 }

geometry/solids/Boolean/src/G4SubtractionSolid.cc:

466 G4Polyhedron*
467 G4SubtractionSolid::CreatePolyhedron () const
468 {
469   G4Polyhedron* pA = fPtrSolidA->GetPolyhedron();
470   G4Polyhedron* pB = fPtrSolidB->GetPolyhedron();
471   if (pA && pB)
472   {
473     G4Polyhedron* resultant = new G4Polyhedron (pA->subtract(*pB));
474     return resultant;
475   }
476   else
477   {
478     std::ostringstream oss;
479     oss << "Solid - " << GetName()
480         << " - one of the Boolean components has no" << G4endl
481         << " corresponding polyhedron. Returning NULL !";
482     G4Exception("G4SubtractionSolid::CreatePolyhedron()", "InvalidSetup",
483                 JustWarning, oss.str().c_str());
484     return 0;
485   }
486 }