0030024: Data Exchange - STEP, IGES export support of BRep shapes based on tessellated geometry

Support of reading and writing tessellated geometry is added for the following STEP entities:
- triangulated face
- complex triangulated face
- tessellated shell
- tessellated solid
- tessellated shape representation

Models without BRep geometry (mesh formats like STL, OBJ and so on) are supported for writing to STEP.

New parameters are added to enable/disable tessellated geometry reading and writing:
- read.step.tessellated (On/Off/OnNoBRep) (On by default)
- write.step.tessellated (On/Off/OnNoBRep) (OnNoBRep by default)

OnNoBRep - tessellation is read/written only for entities for which there is no BRep representation.

Faces with poly triangulation are written in STEP as triangulated face entities with one coordinates list per face.
Only one poly triangulation per face (returned by BRep_Tool::Triangulation) is written to STEP.

src/STEPControl/STEPControl_ActorRead.cxx

@@ -88,6 +88,10 @@
 #include <StepShape_ShapeDefinitionRepresentation.hxx>
 #include <StepShape_ShapeRepresentation.hxx>
 #include <StepShape_ShellBasedSurfaceModel.hxx>
+#include <StepVisual_TriangulatedFace.hxx>
+#include <StepVisual_TessellatedShell.hxx>
+#include <StepVisual_TessellatedShapeRepresentation.hxx>
+#include <StepVisual_TessellatedSolid.hxx>
 #include <StepToGeom.hxx>
 #include <StepToTopoDS_Builder.hxx>
 #include <StepToTopoDS_DataMapOfTRI.hxx>
@@ -95,6 +99,7 @@
 #include <StepToTopoDS_Tool.hxx>
 #include <StepToTopoDS_TranslateFace.hxx>
 #include <TColStd_HSequenceOfTransient.hxx>
+#include <TopExp.hxx>
 #include <TopExp_Explorer.hxx>
 #include <TopoDS.hxx>
 #include <TopoDS_Compound.hxx>
@@ -103,6 +108,7 @@
 #include <TopoDS_Shape.hxx>
 #include <TopoDS_Shell.hxx>
 #include <TopoDS_Solid.hxx>
+#include <TopTools_IndexedMapOfShape.hxx>
 #include <TopTools_ListIteratorOfListOfShape.hxx>
 #include <TopTools_ListOfShape.hxx>
 #include <TopTools_MapOfShape.hxx>
@@ -209,6 +215,7 @@ STEPControl_ActorRead::STEPControl_ActorRead()
   myMaxTol(0.0)
 {
 }
+
 // ============================================================================
 // Method  : STEPControl_ActorRead::Recognize
 // Purpose : tells if an entity is valid for transfer by this Actor
@@ -236,6 +243,8 @@ Standard_Boolean  STEPControl_ActorRead::Recognize
     return Standard_False;
   }
 
+  const Standard_Boolean aCanReadTessGeom = (Interface_Static::IVal("read.step.tessellated") != 0);
+
   if (start->IsKind(STANDARD_TYPE(StepShape_FacetedBrep))) return Standard_True;
   if (start->IsKind(STANDARD_TYPE(StepShape_BrepWithVoids))) return Standard_True;
   if (start->IsKind(STANDARD_TYPE(StepShape_ManifoldSolidBrep))) return Standard_True;
@@ -246,6 +255,10 @@ Standard_Boolean  STEPControl_ActorRead::Recognize
   if (start->IsKind(STANDARD_TYPE(StepShape_FaceSurface))) return Standard_True;
   if (start->IsKind(STANDARD_TYPE(StepShape_EdgeBasedWireframeModel))) return Standard_True;
   if (start->IsKind(STANDARD_TYPE(StepShape_FaceBasedSurfaceModel))) return Standard_True;
+  if (aCanReadTessGeom && start->IsKind(STANDARD_TYPE(StepVisual_TessellatedFace))) return Standard_True;
+  if (aCanReadTessGeom && start->IsKind(STANDARD_TYPE(StepVisual_TessellatedShell))) return Standard_True;
+  if (aCanReadTessGeom && start->IsKind(STANDARD_TYPE(StepVisual_TessellatedSolid))) return Standard_True;
+  if (aCanReadTessGeom && start->IsKind(STANDARD_TYPE(StepVisual_TessellatedShapeRepresentation))) return Standard_True;
 
 
 //  REPRESENTATION_RELATIONSHIP et consorts : on regarde le contenu ...
@@ -859,6 +872,7 @@ Handle(TransferBRep_ShapeBinder) STEPControl_ActorRead::TransferEntity(
   gp_Trsf aTrsf;
   Message_ProgressScope aPSRoot(theProgress, "Sub-assembly", isManifold ? 1 : 2);
   Message_ProgressScope aPS (aPSRoot.Next(), "Transfer", nb);
+  TopTools_IndexedMapOfShape aCompoundedShapes;
   for (Standard_Integer i = 1; i <= nb && aPS.More(); i ++)
   {
     Message_ProgressRange aRange = aPS.Next();
@@ -915,8 +929,13 @@ Handle(TransferBRep_ShapeBinder) STEPControl_ActorRead::TransferEntity(
     TopoDS_Shape theResult = TransferBRep::ShapeResult (binder);
     if (!theResult.IsNull()) {
       OneResult = theResult;
-      B.Add(comp, theResult);
-      nsh ++;
+      if (!aCompoundedShapes.Contains(theResult)) 
+      {
+        aCompoundedShapes.Add(theResult);
+        TopExp::MapShapes(theResult, aCompoundedShapes, Standard_False, Standard_False);
+        B.Add(comp, theResult);
+        nsh++;
+      }
     }
   }
 
@@ -1396,6 +1415,8 @@ Handle(TransferBRep_ShapeBinder) STEPControl_ActorRead::TransferEntity
   // Start progress scope (no need to check if progress exists -- it is safe)
   Message_ProgressScope aPS(theProgress, "Transfer stage", isManifold ? 2 : 1);
 
+  const Standard_Boolean aReadTessellatedWhenNoBRepOnly = (Interface_Static::IVal("read.step.tessellated") == 2);
+  Standard_Boolean aHasGeom = Standard_True;
   try {
     OCC_CATCH_SIGNALS
     Message_ProgressRange aRange = aPS.Next();
@@ -1431,6 +1452,27 @@ Handle(TransferBRep_ShapeBinder) STEPControl_ActorRead::TransferEntity
       myShapeBuilder.Init(GetCasted(StepShape_FaceBasedSurfaceModel, start), TP);
       found = Standard_True;
     }
+    // TODO: Normally, StepVisual_Tessellated* entities should be processed after
+    //       StepShape_* entities in order to resolve links to BRep topological objects.
+    //       Currently it is not guaranteed and might require changes in the processing order.
+    else if (start->IsKind(STANDARD_TYPE(StepVisual_TessellatedSolid))) 
+    {
+      myShapeBuilder.Init(GetCasted(StepVisual_TessellatedSolid, start), TP, 
+                          aReadTessellatedWhenNoBRepOnly, aHasGeom, aRange);
+      found = Standard_True;
+    }
+    else if (start->IsKind(STANDARD_TYPE(StepVisual_TessellatedShell))) 
+    {
+      myShapeBuilder.Init(GetCasted(StepVisual_TessellatedShell, start), TP, 
+                          aReadTessellatedWhenNoBRepOnly, aHasGeom, aRange);
+      found = Standard_True;
+    }
+    else if (start->IsKind(STANDARD_TYPE(StepVisual_TessellatedFace))) 
+    {
+      myShapeBuilder.Init(GetCasted(StepVisual_TessellatedFace, start), TP, 
+                          aReadTessellatedWhenNoBRepOnly, aHasGeom);
+      found = Standard_True;
+    }
   }
   catch(Standard_Failure const&) {
     TP->AddFail(start,"Exception is raised. Entity was not translated.");
@@ -1444,7 +1486,8 @@ Handle(TransferBRep_ShapeBinder) STEPControl_ActorRead::TransferEntity
   if (found && myShapeBuilder.IsDone()) {
     mappedShape = myShapeBuilder.Value();
     // Apply ShapeFix (on manifold shapes only. Non-manifold topology is processed separately: ssv; 13.11.2010)
-    if (isManifold) {
+    if (isManifold && aHasGeom) 
+    {
       Handle(Standard_Transient) info;
       mappedShape = 
         XSAlgo::AlgoContainer()->ProcessShape( mappedShape, myPrecision, myMaxTol,