0026338: STL export (especially binary) needs a lot of time if selected export path is not local

Method StlAPI_Writer::Write() is reimplemented to write triangulation directly, without conversion to StlMesh_Mesh.

New DRAW command "tessellate" is added to generate rapidly triangulation of prescribed size (on surface).

Command "tricheck" is protected to deal correctly with triangulation without UV data.

New tests added: perf de bug26338_1 and _2; bugs stlvrml bug26338

Correction of testing environment

src/StlAPI/StlAPI_ErrorStatus.hxx

@@ -23,7 +23,8 @@ enum StlAPI_ErrorStatus
 {
 StlAPI_StatusOK,
 StlAPI_MeshIsEmpty,
-StlAPI_CannotOpenFile
+StlAPI_CannotOpenFile,
+StlAPI_WriteError
 };
 
 #endif // _StlAPI_ErrorStatus_HeaderFile

src/StlAPI/StlAPI_Writer.cxx

@@ -15,11 +15,16 @@
 #include <Bnd_Box.hxx>
 #include <BRepBndLib.hxx>
 #include <OSD_Path.hxx>
+#include <OSD_OpenFile.hxx>
 #include <RWStl.hxx>
 #include <StlAPI_Writer.hxx>
 #include <StlMesh_Mesh.hxx>
 #include <StlTransfer.hxx>
-#include <TopoDS_Shape.hxx>
+#include <BRep_Tool.hxx>
+#include <TopoDS.hxx>
+#include <TopoDS_Face.hxx>
+#include <TopExp_Explorer.hxx>
+#include <Poly_Triangulation.hxx>
 
 StlAPI_Writer::StlAPI_Writer()
 {
@@ -32,26 +37,172 @@ Standard_Boolean& StlAPI_Writer::ASCIIMode()
   return theASCIIMode;
 }
 
-StlAPI_ErrorStatus StlAPI_Writer::Write(const TopoDS_Shape& theShape, const Standard_CString theFileName)
+// Auxiliary tools
+namespace
 {
-  OSD_Path aFile(theFileName);
-  StlTransfer::RetrieveMesh(theShape, theStlMesh);
-
-  if (theStlMesh.IsNull() || theStlMesh->IsEmpty())
-    return StlAPI_MeshIsEmpty;
-
-  // Write the built mesh
-  Standard_Boolean wasFileOpened = Standard_False;
-  if (theASCIIMode) {
-    wasFileOpened = RWStl::WriteAscii(theStlMesh, aFile);
-    }  
-  else {
-    wasFileOpened = RWStl::WriteBinary(theStlMesh, aFile);
+  // Tool to get triangles from triangulation taking into account face
+  // orientation and location
+  class TriangleAccessor
+  {
+  public:
+    TriangleAccessor (const TopoDS_Face& aFace)
+    {
+      TopLoc_Location aLoc;
+      myPoly = BRep_Tool::Triangulation (aFace, aLoc);
+      myTrsf = aLoc.Transformation();
+      myNbTriangles = (myPoly.IsNull() ? 0 : myPoly->Triangles().Length());
+      myInvert = (aFace.Orientation() == TopAbs_REVERSED);
+      if (myTrsf.IsNegative())
+        myInvert = ! myInvert;
     }
 
-  if (!wasFileOpened)
-    return StlAPI_CannotOpenFile;
+    int NbTriangles () const { return myNbTriangles; } 
 
-  return StlAPI_StatusOK;
+    // get i-th triangle and outward normal
+    void GetTriangle (int iTri, gp_Vec &theNormal, gp_Pnt &thePnt1, gp_Pnt &thePnt2, gp_Pnt &thePnt3)
+    {
+      // get positions of nodes
+      int iNode1, iNode2, iNode3;
+      myPoly->Triangles()(iTri).Get (iNode1, iNode2, iNode3);
+      thePnt1 = myPoly->Nodes()(iNode1);
+      thePnt2 = myPoly->Nodes()(myInvert ? iNode3 : iNode2);
+      thePnt3 = myPoly->Nodes()(myInvert ? iNode2 : iNode3);
+
+      // apply transormation if not identity
+      if (myTrsf.Form() != gp_Identity)
+      {
+        thePnt1.Transform (myTrsf);
+        thePnt2.Transform (myTrsf);
+        thePnt3.Transform (myTrsf);
+      }
+
+      // calculate normal
+      theNormal = (thePnt2.XYZ() - thePnt1.XYZ()) ^ (thePnt3.XYZ() - thePnt1.XYZ());
+      Standard_Real aNorm = theNormal.Magnitude();
+      if (aNorm > gp::Resolution())
+        theNormal /= aNorm;
+    }
+
+  private:
+    Handle(Poly_Triangulation) myPoly;
+    gp_Trsf myTrsf;
+    int myNbTriangles;
+    bool myInvert;
+  };
+
+  // convert to float and, on big-endian platform, to little-endian representation
+  inline float convertFloat (Standard_Real aValue)
+  {
+#ifdef OCCT_BINARY_FILE_DO_INVERSE
+    return OSD_BinaryFile::InverseShortReal ((float)aValue);
+#else
+    return (float)aValue;
+#endif
+  }
+}
+
+StlAPI_ErrorStatus StlAPI_Writer::Write(const TopoDS_Shape& theShape, const Standard_CString theFileName)
+{
+  // open file
+  FILE* aFile = OSD_OpenFile (theFileName, "wb");
+  if (!aFile)
+    return StlAPI_CannotOpenFile;
+
+  // write
+  if (theASCIIMode)
+  {
+    // header 
+    Fprintf (aFile, "solid shape, STL ascii file, created with Open CASCADE Technology\n");
+
+    // facets
+    for (TopExp_Explorer exp (theShape, TopAbs_FACE); exp.More(); exp.Next())
+    {
+      TriangleAccessor aTool (TopoDS::Face (exp.Current()));
+      for (int iTri = 1; iTri <= aTool.NbTriangles(); iTri++)
+      {
+        gp_Vec aNorm;
+        gp_Pnt aPnt1, aPnt2, aPnt3;
+        aTool.GetTriangle (iTri, aNorm, aPnt1, aPnt2, aPnt3);
+
+        Fprintf (aFile,
+          " facet normal %12e %12e %12e\n"
+          "   outer loop\n"
+          "     vertex %12e %12e %12e\n"
+          "     vertex %12e %12e %12e\n"
+          "     vertex %12e %12e %12e\n"
+          "   endloop\n"
+          " endfacet\n",
+          aNorm.X(), aNorm.Y(), aNorm.Z(),
+          aPnt1.X(), aPnt1.Y(), aPnt1.Z(),
+          aPnt2.X(), aPnt2.Y(), aPnt2.Z(),
+          aPnt3.X(), aPnt3.Y(), aPnt3.Z());
+      }
+    }
+
+    // footer
+    Fprintf (aFile, "endsolid shape\n");
+  }
+  else
+  {
+    // header block (meaningless 80 bytes)
+    Fprintf (aFile, "%-80.80s", "STL binary file, created with Open CASCADE Technology");
+
+    // number of facets
+    int32_t aNbTri = 0;
+    for (TopExp_Explorer exp (theShape, TopAbs_FACE); exp.More(); exp.Next())
+    {
+      TopLoc_Location aLoc;
+      Handle(Poly_Triangulation) aPoly =
+        BRep_Tool::Triangulation (TopoDS::Face (exp.Current()), aLoc);
+      if (! aPoly.IsNull())
+        aNbTri += aPoly->NbTriangles();
+    }
+    // suppose that number of triangles must be little endian...
+#ifdef OCCT_BINARY_FILE_DO_INVERSE
+    aNbTri = OSD_BinaryFile::InverseInteger (aNbTri);
+#endif
+    fwrite (&aNbTri, sizeof(int32_t), 1, aFile);
+
+    // facets
+    struct Facet {
+      float nx, ny, nz;
+      float x1, y1, z1;
+      float x2, y2, z2;
+      float x3, y3, z3;
+      uint16_t dummy;
+    } f;
+    f.dummy = 0;
+    for (TopExp_Explorer exp (theShape, TopAbs_FACE); exp.More(); exp.Next())
+    {
+      TriangleAccessor aTool (TopoDS::Face (exp.Current()));
+      for (int iTri = 1; iTri <= aTool.NbTriangles(); iTri++)
+      {
+        gp_Vec aNorm;
+        gp_Pnt aPnt1, aPnt2, aPnt3;
+        aTool.GetTriangle (iTri, aNorm, aPnt1, aPnt2, aPnt3);
+
+        f.nx = convertFloat (aNorm.X());
+        f.ny = convertFloat (aNorm.Y());
+        f.nz = convertFloat (aNorm.Z());
+
+        f.x1 = convertFloat (aPnt1.X());
+        f.y1 = convertFloat (aPnt1.Y());
+        f.z1 = convertFloat (aPnt1.Z());
+
+        f.x2 = convertFloat (aPnt2.X());
+        f.y2 = convertFloat (aPnt2.Y());
+        f.z2 = convertFloat (aPnt2.Z());
+
+        f.x3 = convertFloat (aPnt3.X());
+        f.y3 = convertFloat (aPnt3.Y());
+        f.z3 = convertFloat (aPnt3.Z());
+
+        fwrite (&f, 50 /* 50 bytes per facet */, 1, aFile);
+      }
+    }
+  }
+
+  fclose (aFile);
+  return ferror(aFile) ? StlAPI_WriteError : StlAPI_StatusOK;
 }